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java.awt
class Component

java.lang.Object extended by java.awt.Component
All Implemented Interfaces:
MenuContainer, ImageObserver, Serializable
Direct Known Subclasses:
Button, Canvas, Checkbox, Choice, Container, Label, List, Scrollbar, TextComponent

public abstract class Component
extends Object
implements ImageObserver, MenuContainer, Serializable

A component is an object having a graphical representation that can be displayed on the screen and that can interact with the user. Examples of components are the buttons, checkboxes, and scrollbars of a typical graphical user interface.

The Component class is the abstract superclass of the nonmenu-related Abstract Window Toolkit components. Class Component can also be extended directly to create a lightweight component. A lightweight component is a component that is not associated with a native opaque window.

Serialization

It is important to note that only AWT listeners which conform to the Serializable protocol will be saved when the object is stored. If an AWT object has listeners that aren't marked serializable, they will be dropped at writeObject time. Developers will need, as always, to consider the implications of making an object serializable. One situation to watch out for is this:
    import java.awt.*;
    import java.awt.event.*;
    import java.io.Serializable;
    
    class MyApp implements ActionListener, Serializable
    {
        BigObjectThatShouldNotBeSerializedWithAButton bigOne;
        Button aButton = new Button();
      
        MyApp()
        {
            // Oops, now aButton has a listener with a reference
            // to bigOne!
            aButton.addActionListener(this);
        }
    
        public void actionPerformed(ActionEvent e)
        {
            System.out.println("Hello There");
        }
    }
 
In this example, serializing aButton by itself will cause MyApp and everything it refers to to be serialized as well. The problem is that the listener is serializable by coincidence, not by design. To separate the decisions about MyApp and the ActionListener being serializable one can use a nested class, as in the following example:
    import java.awt.*;
    import java.awt.event.*;
    import java.io.Serializable;

    class MyApp java.io.Serializable
    {
         BigObjectThatShouldNotBeSerializedWithAButton bigOne;
         Button aButton = new Button();

         static class MyActionListener implements ActionListener
         {
             public void actionPerformed(ActionEvent e)
             {
                 System.out.println("Hello There");
             }
         }
 
         MyApp()
         {
             aButton.addActionListener(new MyActionListener());
         }
    }
 

Note: For more information on the paint mechanisms utilitized by AWT and Swing, including information on how to write the most efficient painting code, see Painting in AWT and Swing.

For details on the focus subsystem, see How to Use the Focus Subsystem, a section in The Java Tutorial, and the Focus Specification for more information.


Nested Class Summary
protected abstract class

           Inner class of Component used to provide default support for accessibility.
static enum

           Enumeration of the common ways the baseline of a component can change as the size changes.
protected class

           Inner class for blitting offscreen surfaces to a component.
protected class

           Inner class for flipping buffers on a component.
 
Field Summary
static float BOTTOM_ALIGNMENT
          Ease-of-use constant for getAlignmentY.
static float CENTER_ALIGNMENT
          Ease-of-use constant for getAlignmentY and getAlignmentX.
static float LEFT_ALIGNMENT
          Ease-of-use constant for getAlignmentX.
static float RIGHT_ALIGNMENT
          Ease-of-use constant for getAlignmentX.
static float TOP_ALIGNMENT
          Ease-of-use constant for getAlignmentY().
 
Constructor Summary
protected

          Constructs a new component.
 
Method Summary
 boolean
action(Event evt, Object what)

          
 void
add(PopupMenu popup)

          Adds the specified popup menu to the component.
 void

          Adds the specified component listener to receive component events from this component.
 void

          Adds the specified focus listener to receive focus events from this component when this component gains input focus.
 void

          Adds the specified hierarchy bounds listener to receive hierarchy bounds events from this component when the hierarchy to which this container belongs changes.
 void

          Adds the specified hierarchy listener to receive hierarchy changed events from this component when the hierarchy to which this container belongs changes.
 void

          Adds the specified input method listener to receive input method events from this component.
 void

          Adds the specified key listener to receive key events from this component.
 void

          Adds the specified mouse listener to receive mouse events from this component.
 void

          Adds the specified mouse motion listener to receive mouse motion events from this component.
 void

          Adds the specified mouse wheel listener to receive mouse wheel events from this component.
 void

          Makes this Component displayable by connecting it to a native screen resource.
 void

          Adds a PropertyChangeListener to the listener list.
 void

          Adds a PropertyChangeListener to the listener list for a specific property.
 void

          Sets the ComponentOrientation property of this component and all components contained within it.
 boolean

          Returns whether the Set of focus traversal keys for the given focus traversal operation has been explicitly defined for this Component.
 Rectangle

          
 int
checkImage(Image image, ImageObserver observer)

          Returns the status of the construction of a screen representation of the specified image.
 int
checkImage(Image image, int width, int height, ImageObserver observer)

          Returns the status of the construction of a screen representation of the specified image.
protected AWTEvent
coalesceEvents(AWTEvent existingEvent, AWTEvent newEvent)

          Potentially coalesce an event being posted with an existing event.
 boolean
contains(int x, int y)

          Checks whether this component "contains" the specified point, where x and y are defined to be relative to the coordinate system of this component.
 boolean

          Checks whether this component "contains" the specified point, where the point's x and y coordinates are defined to be relative to the coordinate system of this component.
 Image

          Creates an image from the specified image producer.
 Image
createImage(int width, int height)

          Creates an off-screen drawable image to be used for double buffering.
 VolatileImage
createVolatileImage(int width, int height)

          Creates a volatile off-screen drawable image to be used for double buffering.
 VolatileImage
createVolatileImage(int width, int height, ImageCapabilities caps)

          Creates a volatile off-screen drawable image, with the given capabilities.
 void

          
 void

          
protected void
disableEvents(long eventsToDisable)

          Disables the events defined by the specified event mask parameter from being delivered to this component.
 void

          Dispatches an event to this component or one of its sub components.
 void

          Prompts the layout manager to lay out this component.
 void

          
 void
enable(boolean b)

          
protected void
enableEvents(long eventsToEnable)

          Enables the events defined by the specified event mask parameter to be delivered to this component.
 void
enableInputMethods(boolean enable)

          Enables or disables input method support for this component.
protected void
firePropertyChange(String propertyName, boolean oldValue, boolean newValue)

          Support for reporting bound property changes for boolean properties.
 void
firePropertyChange(String propertyName, byte oldValue, byte newValue)

          Reports a bound property change.
 void
firePropertyChange(String propertyName, char oldValue, char newValue)

          Reports a bound property change.
 void
firePropertyChange(String propertyName, double oldValue, double newValue)

          Reports a bound property change.
 void
firePropertyChange(String propertyName, float oldValue, float newValue)

          Reports a bound property change.
protected void
firePropertyChange(String propertyName, int oldValue, int newValue)

          Support for reporting bound property changes for integer properties.
 void
firePropertyChange(String propertyName, long oldValue, long newValue)

          Reports a bound property change.
protected void
firePropertyChange(String propertyName, Object oldValue, Object newValue)

          Support for reporting bound property changes for Object properties.
 void
firePropertyChange(String propertyName, short oldValue, short newValue)

          Reports a bound property change.
 AccessibleContext

          Gets the AccessibleContext associated with this Component.
 float

          Returns the alignment along the x axis.
 float

          Returns the alignment along the y axis.
 Color

          Gets the background color of this component.
 int
getBaseline(int width, int height)

          Returns the baseline.
 Component.BaselineResizeBehavior

          Returns an enum indicating how the baseline of the component changes as the size changes.
 Rectangle

          Gets the bounds of this component in the form of a Rectangle object.
 Rectangle

          Stores the bounds of this component into "return value" rv and return rv.
 ColorModel

          Gets the instance of ColorModel used to display the component on the output device.
 Component
getComponentAt(int x, int y)

          Determines if this component or one of its immediate subcomponents contains the (xy) location, and if so, returns the containing component.
 Component

          Returns the component or subcomponent that contains the specified point.
 ComponentListener[]

          Returns an array of all the component listeners registered on this component.
 ComponentOrientation

          Retrieves the language-sensitive orientation that is to be used to order the elements or text within this component.
 Cursor

          Gets the cursor set in the component.
 DropTarget

          Gets the DropTarget associated with this Component.
 Container

          Returns the Container which is the focus cycle root of this Component's focus traversal cycle.
 FocusListener[]

          Returns an array of all the focus listeners registered on this component.
 Set

          Returns the Set of focus traversal keys for a given traversal operation for this Component.
 boolean

          Returns whether focus traversal keys are enabled for this Component.
 Font

          Gets the font of this component.
 FontMetrics

          Gets the font metrics for the specified font.
 Color

          Gets the foreground color of this component.
 Graphics

          Creates a graphics context for this component.
 GraphicsConfiguration

          Gets the GraphicsConfiguration associated with this Component.
 int

          Returns the current height of this component.
 HierarchyBoundsListener[]

          Returns an array of all the hierarchy bounds listeners registered on this component.
 HierarchyListener[]

          Returns an array of all the hierarchy listeners registered on this component.
 boolean

          
 InputContext

          Gets the input context used by this component for handling the communication with input methods when text is entered in this component.
 InputMethodListener[]

          Returns an array of all the input method listeners registered on this component.
 InputMethodRequests

          Gets the input method request handler which supports requests from input methods for this component.
 KeyListener[]

          Returns an array of all the key listeners registered on this component.
 EventListener[]
getListeners(Class listenerType)

          Returns an array of all the objects currently registered as FooListeners upon this Component.
 Locale

          Gets the locale of this component.
 Point

          Gets the location of this component in the form of a point specifying the component's top-left corner.
 Point

          Stores the x,y origin of this component into "return value" rv and return rv.
 Point

          Gets the location of this component in the form of a point specifying the component's top-left corner in the screen's coordinate space.
 Dimension

          Gets the maximum size of this component.
 Dimension

          Gets the mininimum size of this component.
 MouseListener[]

          Returns an array of all the mouse listeners registered on this component.
 MouseMotionListener[]

          Returns an array of all the mouse motion listeners registered on this component.
 Point

          Returns the position of the mouse pointer in this Component's coordinate space if the Component is directly under the mouse pointer, otherwise returns null.
 MouseWheelListener[]

          Returns an array of all the mouse wheel listeners registered on this component.
 String

          Gets the name of the component.
 Container

          Gets the parent of this component.
 ComponentPeer

          
 Dimension

          Gets the preferred size of this component.
 PropertyChangeListener[]

          Returns an array of all the property change listeners registered on this component.
 PropertyChangeListener[]

          Returns an array of all the listeners which have been associated with the named property.
 Dimension

          Returns the size of this component in the form of a Dimension object.
 Dimension

          Stores the width/height of this component into "return value" rv and return rv.
 Toolkit

          Gets the toolkit of this component.
 Object

          Gets this component's locking object (the object that owns the thread sychronization monitor) for AWT component-tree and layout operations.
 int

          Returns the current width of this component.
 int

          Returns the current x coordinate of the components origin.
 int

          Returns the current y coordinate of the components origin.
 boolean
gotFocus(Event evt, Object what)

          
 boolean

          
 boolean

          Returns true if this Component is the focus owner.
 void

          
 boolean
imageUpdate(Image img, int infoflags, int x, int y, int w, int h)

          Repaints the component when the image has changed.
 boolean
inside(int x, int y)

          
 void

          Invalidates this component.
 boolean

          Returns whether the background color has been explicitly set for this Component.
 boolean

          Returns whether the cursor has been explicitly set for this Component.
 boolean

          Determines whether this component is displayable.
 boolean

          Returns true if this component is painted to an offscreen image ("buffer") that's copied to the screen later.
 boolean

          Determines whether this component is enabled.
 boolean

          Returns whether this Component can be focused.
 boolean

          Returns whether the specified Container is the focus cycle root of this Component's focus traversal cycle.
 boolean

          Returns true if this Component is the focus owner.
 boolean

          Returns whether this Component can become the focus owner.
 boolean

          Returns whether the font has been explicitly set for this Component.
 boolean

          Returns whether the foreground color has been explicitly set for this Component.
 boolean

          A lightweight component doesn't have a native toolkit peer.
 boolean

          Returns true if the maximum size has been set to a non-null value otherwise returns false.
 boolean

          Returns whether or not setMinimumSize has been invoked with a non-null value.
 boolean

          Returns true if this component is completely opaque, returns false by default.
 boolean

          Returns true if the preferred size has been set to a non-null value otherwise returns false.
 boolean

          Determines whether this component is showing on screen.
 boolean

          Determines whether this component is valid.
 boolean

          Determines whether this component should be visible when its parent is visible.
 boolean
keyDown(Event evt, int key)

          
 boolean
keyUp(Event evt, int key)

          
 void

          
 void

          Prints a listing of this component to the standard system output stream System.out.
 void

          Prints a listing of this component to the specified output stream.
 void
list(PrintStream out, int indent)

          Prints out a list, starting at the specified indentation, to the specified print stream.
 void

          Prints a listing to the specified print writer.
 void
list(PrintWriter out, int indent)

          Prints out a list, starting at the specified indentation, to the specified print writer.
 Component
locate(int x, int y)

          
 Point

          
 boolean
lostFocus(Event evt, Object what)

          
 Dimension

          
 boolean
mouseDown(Event evt, int x, int y)

          
 boolean
mouseDrag(Event evt, int x, int y)

          
 boolean
mouseEnter(Event evt, int x, int y)

          
 boolean
mouseExit(Event evt, int x, int y)

          
 boolean
mouseMove(Event evt, int x, int y)

          
 boolean
mouseUp(Event evt, int x, int y)

          
 void
move(int x, int y)

          
 void

          
 void

          Paints this component.
 void

          Paints this component and all of its subcomponents.
protected String

          Returns a string representing the state of this component.
 boolean

          
 Dimension

          
 boolean
prepareImage(Image image, ImageObserver observer)

          Prepares an image for rendering on this component.
 boolean
prepareImage(Image image, int width, int height, ImageObserver observer)

          Prepares an image for rendering on this component at the specified width and height.
 void

          Prints this component.
 void

          Prints this component and all of its subcomponents.
protected void

          Processes component events occurring on this component by dispatching them to any registered ComponentListener objects.
protected void

          Processes events occurring on this component.
protected void

          Processes focus events occurring on this component by dispatching them to any registered FocusListener objects.
protected void

          Processes hierarchy bounds events occurring on this component by dispatching them to any registered HierarchyBoundsListener objects.
protected void

          Processes hierarchy events occurring on this component by dispatching them to any registered HierarchyListener objects.
protected void

          Processes input method events occurring on this component by dispatching them to any registered InputMethodListener objects.
protected void

          Processes key events occurring on this component by dispatching them to any registered KeyListener objects.
protected void

          Processes mouse events occurring on this component by dispatching them to any registered MouseListener objects.
protected void

          Processes mouse motion events occurring on this component by dispatching them to any registered MouseMotionListener objects.
protected void

          Processes mouse wheel events occurring on this component by dispatching them to any registered MouseWheelListener objects.
 void

          Removes the specified popup menu from the component.
 void

          Removes the specified component listener so that it no longer receives component events from this component.
 void

          Removes the specified focus listener so that it no longer receives focus events from this component.
 void

          Removes the specified hierarchy bounds listener so that it no longer receives hierarchy bounds events from this component.
 void

          Removes the specified hierarchy listener so that it no longer receives hierarchy changed events from this component.
 void

          Removes the specified input method listener so that it no longer receives input method events from this component.
 void

          Removes the specified key listener so that it no longer receives key events from this component.
 void

          Removes the specified mouse listener so that it no longer receives mouse events from this component.
 void

          Removes the specified mouse motion listener so that it no longer receives mouse motion events from this component.
 void

          Removes the specified mouse wheel listener so that it no longer receives mouse wheel events from this component.
 void

          Makes this Component undisplayable by destroying it native screen resource.
 void

          Removes a PropertyChangeListener from the listener list.
 void

          Removes a PropertyChangeListener from the listener list for a specific property.
 void

          Repaints this component.
 void
repaint(int x, int y, int width, int height)

          Repaints the specified rectangle of this component.
 void
repaint(long tm)

          Repaints the component.
 void
repaint(long tm, int x, int y, int width, int height)

          Repaints the specified rectangle of this component within tm milliseconds.
 void

          Requests that this Component get the input focus, and that this Component's top-level ancestor become the focused Window.
protected boolean
requestFocus(boolean temporary)

          Requests that this Component get the input focus, and that this Component's top-level ancestor become the focused Window.
 boolean

          Requests that this Component get the input focus, if this Component's top-level ancestor is already the focused Window.
protected boolean
requestFocusInWindow(boolean temporary)

          Requests that this Component get the input focus, if this Component's top-level ancestor is already the focused Window.
 void
reshape(int x, int y, int width, int height)

          
 void

          
 void
resize(int width, int height)

          
 void

          Sets the background color of this component.
 void
setBounds(int x, int y, int width, int height)

          Moves and resizes this component.
 void

          Moves and resizes this component to conform to the new bounding rectangle r.
 void

          Sets the language-sensitive orientation that is to be used to order the elements or text within this component.
 void
setCursor(Cursor cursor)

          Sets the cursor image to the specified cursor.
 void

          Associate a DropTarget with this component.
 void
setEnabled(boolean b)

          Enables or disables this component, depending on the value of the parameter b.
 void
setFocusable(boolean focusable)

          Sets the focusable state of this Component to the specified value.
 void
setFocusTraversalKeys(int id, Set keystrokes)

          Sets the focus traversal keys for a given traversal operation for this Component.
 void
setFocusTraversalKeysEnabled(boolean focusTraversalKeysEnabled)

          Sets whether focus traversal keys are enabled for this Component.
 void

          Sets the font of this component.
 void

          Sets the foreground color of this component.
 void
setIgnoreRepaint(boolean ignoreRepaint)

          Sets whether or not paint messages received from the operating system should be ignored.
 void

          Sets the locale of this component.
 void
setLocation(int x, int y)

          Moves this component to a new location.
 void

          Moves this component to a new location.
 void

          Sets the maximum size of this component to a constant value.
 void

          Sets the minimum size of this component to a constant value.
 void

          Sets the name of the component to the specified string.
 void
setPreferredSize(Dimension preferredSize)

          Sets the preferred size of this component to a constant value.
 void

          Resizes this component so that it has width d.width and height d.height.
 void
setSize(int width, int height)

          Resizes this component so that it has width width and height height.
 void
setVisible(boolean b)

          Shows or hides this component depending on the value of parameter b.
 void

          
 void
show(boolean b)

          
 Dimension

          
 String

          Returns a string representation of this component and its values.
 void

          Transfers the focus to the next component, as though this Component were the focus owner.
 void

          Transfers the focus to the previous component, as though this Component were the focus owner.
 void

          Transfers the focus up one focus traversal cycle.
 void

          Updates this component.
 void

          Ensures that this component has a valid layout.
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Field Detail

BOTTOM_ALIGNMENT

public static final float BOTTOM_ALIGNMENT
Ease-of-use constant for getAlignmentY. Specifies an alignment to the bottom of the component.

CENTER_ALIGNMENT

public static final float CENTER_ALIGNMENT
Ease-of-use constant for getAlignmentY and getAlignmentX. Specifies an alignment to the center of the component

LEFT_ALIGNMENT

public static final float LEFT_ALIGNMENT
Ease-of-use constant for getAlignmentX. Specifies an alignment to the left side of the component.

RIGHT_ALIGNMENT

public static final float RIGHT_ALIGNMENT
Ease-of-use constant for getAlignmentX. Specifies an alignment to the right side of the component.

TOP_ALIGNMENT

public static final float TOP_ALIGNMENT
Ease-of-use constant for getAlignmentY(). Specifies an alignment to the top of the component.
Constructor Detail

Component

protected Component()
Constructs a new component. Class Component can be extended directly to create a lightweight component that does not utilize an opaque native window. A lightweight component must be hosted by a native container somewhere higher up in the component tree (for example, by a Frame object).

Method Detail

action

public boolean action(Event evt,
                      Object what)
Parameters:
evt
what

add

public synchronized void add(PopupMenu popup)
Adds the specified popup menu to the component.

Parameters:
popup - the popup menu to be added to the component.

addComponentListener

public synchronized void addComponentListener(ComponentListener l)
Adds the specified component listener to receive component events from this component. If listener l is null, no exception is thrown and no action is performed.

Refer to AWT Threading Issues for details on AWT's threading model.

Parameters:
l - the component listener

addFocusListener

public synchronized void addFocusListener(FocusListener l)
Adds the specified focus listener to receive focus events from this component when this component gains input focus. If listener l is null, no exception is thrown and no action is performed.

Refer to AWT Threading Issues for details on AWT's threading model.

Parameters:
l - the focus listener

addHierarchyBoundsListener

public void addHierarchyBoundsListener(HierarchyBoundsListener l)
Adds the specified hierarchy bounds listener to receive hierarchy bounds events from this component when the hierarchy to which this container belongs changes. If listener l is null, no exception is thrown and no action is performed.

Refer to AWT Threading Issues for details on AWT's threading model.

Parameters:
l - the hierarchy bounds listener

addHierarchyListener

public void addHierarchyListener(HierarchyListener l)
Adds the specified hierarchy listener to receive hierarchy changed events from this component when the hierarchy to which this container belongs changes. If listener l is null, no exception is thrown and no action is performed.

Refer to AWT Threading Issues for details on AWT's threading model.

Parameters:
l - the hierarchy listener

addInputMethodListener

public synchronized void addInputMethodListener(InputMethodListener l)
Adds the specified input method listener to receive input method events from this component. A component will only receive input method events from input methods if it also overrides getInputMethodRequests to return an InputMethodRequests instance. If listener l is null, no exception is thrown and no action is performed.

Refer to AWT Threading Issues for details on AWT's threading model.

Parameters:
l - the input method listener

addKeyListener

public synchronized void addKeyListener(KeyListener l)
Adds the specified key listener to receive key events from this component. If l is null, no exception is thrown and no action is performed.

Refer to AWT Threading Issues for details on AWT's threading model.

Parameters:
l - the key listener.

addMouseListener

public synchronized void addMouseListener(MouseListener l)
Adds the specified mouse listener to receive mouse events from this component. If listener l is null, no exception is thrown and no action is performed.

Refer to AWT Threading Issues for details on AWT's threading model.

Parameters:
l - the mouse listener

addMouseMotionListener

public synchronized void addMouseMotionListener(MouseMotionListener l)
Adds the specified mouse motion listener to receive mouse motion events from this component. If listener l is null, no exception is thrown and no action is performed.

Refer to AWT Threading Issues for details on AWT's threading model.

Parameters:
l - the mouse motion listener

addMouseWheelListener

public synchronized void addMouseWheelListener(MouseWheelListener l)
Adds the specified mouse wheel listener to receive mouse wheel events from this component. Containers also receive mouse wheel events from sub-components.

For information on how mouse wheel events are dispatched, see the class description for {@link MouseWheelEvent}.

If l is null, no exception is thrown and no action is performed.

Refer to AWT Threading Issues for details on AWT's threading model.

Parameters:
l - the mouse wheel listener

addNotify

public void addNotify()
Makes this Component displayable by connecting it to a native screen resource. This method is called internally by the toolkit and should not be called directly by programs.


addPropertyChangeListener

public synchronized void addPropertyChangeListener(PropertyChangeListener listener)
Adds a PropertyChangeListener to the listener list. The listener is registered for all bound properties of this class, including the following: Note that if this Component is inheriting a bound property, then no event will be fired in response to a change in the inherited property.

If listener is null, no exception is thrown and no action is performed.

Parameters:
listener - the property change listener to be added

addPropertyChangeListener

public synchronized void addPropertyChangeListener(String propertyName,
                                                   PropertyChangeListener listener)
Adds a PropertyChangeListener to the listener list for a specific property. The specified property may be user-defined, or one of the following: Note that if this Component is inheriting a bound property, then no event will be fired in response to a change in the inherited property.

If propertyName or listener is null, no exception is thrown and no action is taken.

Parameters:
propertyName - one of the property names listed above
listener - the property change listener to be added

applyComponentOrientation

public void applyComponentOrientation(ComponentOrientation orientation)
Sets the ComponentOrientation property of this component and all components contained within it.

Parameters:
orientation - the new component orientation of this component and the components contained within it.

areFocusTraversalKeysSet

public boolean areFocusTraversalKeysSet(int id)
Returns whether the Set of focus traversal keys for the given focus traversal operation has been explicitly defined for this Component. If this method returns false, this Component is inheriting the Set from an ancestor, or from the current KeyboardFocusManager.

Parameters:
id - one of KeyboardFocusManager.FORWARD_TRAVERSAL_KEYS, KeyboardFocusManager.BACKWARD_TRAVERSAL_KEYS, or KeyboardFocusManager.UP_CYCLE_TRAVERSAL_KEYS
Returns:
true if the the Set of focus traversal keys for the given focus traversal operation has been explicitly defined for this Component; false otherwise.

bounds

public Rectangle bounds()

checkImage

public int checkImage(Image image,
                      ImageObserver observer)
Returns the status of the construction of a screen representation of the specified image.

This method does not cause the image to begin loading. An application must use the prepareImage method to force the loading of an image.

Information on the flags returned by this method can be found with the discussion of the ImageObserver interface.

Parameters:
image - the Image object whose status is being checked
observer - the ImageObserver object to be notified as the image is being prepared
Returns:
the bitwise inclusive OR of ImageObserver flags indicating what information about the image is currently available

checkImage

public int checkImage(Image image,
                      int width,
                      int height,
                      ImageObserver observer)
Returns the status of the construction of a screen representation of the specified image.

This method does not cause the image to begin loading. An application must use the prepareImage method to force the loading of an image.

The checkImage method of Component calls its peer's checkImage method to calculate the flags. If this component does not yet have a peer, the component's toolkit's checkImage method is called instead.

Information on the flags returned by this method can be found with the discussion of the ImageObserver interface.

Parameters:
image - the Image object whose status is being checked
width - the width of the scaled version whose status is to be checked
height - the height of the scaled version whose status is to be checked
observer - the ImageObserver object to be notified as the image is being prepared
Returns:
the bitwise inclusive OR of ImageObserver flags indicating what information about the image is currently available

coalesceEvents

protected AWTEvent coalesceEvents(AWTEvent existingEvent,
                                  AWTEvent newEvent)
Potentially coalesce an event being posted with an existing event. This method is called by EventQueue.postEvent if an event with the same ID as the event to be posted is found in the queue (both events must have this component as their source). This method either returns a coalesced event which replaces the existing event (and the new event is then discarded), or null to indicate that no combining should be done (add the second event to the end of the queue). Either event parameter may be modified and returned, as the other one is discarded unless null is returned.

This implementation of coalesceEvents coalesces two event types: mouse move (and drag) events, and paint (and update) events. For mouse move events the last event is always returned, causing intermediate moves to be discarded. For paint events, the new event is coalesced into a complex RepaintArea in the peer. The new AWTEvent is always returned.

Parameters:
existingEvent - the event already on the EventQueue
newEvent - the event being posted to the EventQueue
Returns:
a coalesced event, or null indicating that no coalescing was done

contains

public boolean contains(int x,
                        int y)
Checks whether this component "contains" the specified point, where x and y are defined to be relative to the coordinate system of this component.

Parameters:
x - the x coordinate of the point
y - the y coordinate of the point

contains

public boolean contains(Point p)
Checks whether this component "contains" the specified point, where the point's x and y coordinates are defined to be relative to the coordinate system of this component.

Parameters:
p - the point

createImage

public Image createImage(ImageProducer producer)
Creates an image from the specified image producer.

Parameters:
producer - the image producer
Returns:
the image produced

createImage

public Image createImage(int width,
                         int height)
Creates an off-screen drawable image to be used for double buffering.

Parameters:
width - the specified width
height - the specified height
Returns:
an off-screen drawable image, which can be used for double buffering. The return value may be null if the component is not displayable. This will always happen if GraphicsEnvironment.isHeadless() returns true.

createVolatileImage

public VolatileImage createVolatileImage(int width,
                                         int height)
Creates a volatile off-screen drawable image to be used for double buffering.

Parameters:
width - the specified width.
height - the specified height.
Returns:
an off-screen drawable image, which can be used for double buffering. The return value may be null if the component is not displayable. This will always happen if GraphicsEnvironment.isHeadless() returns true.

createVolatileImage

public VolatileImage createVolatileImage(int width,
                                         int height,
                                         ImageCapabilities caps)
                                  throws AWTException
Creates a volatile off-screen drawable image, with the given capabilities. The contents of this image may be lost at any time due to operating system issues, so the image must be managed via the VolatileImage interface.

Parameters:
width - the specified width.
height - the specified height.
caps - the image capabilities
Returns:
a VolatileImage object, which can be used to manage surface contents loss and capabilities.
Throws:
AWTException - if an image with the specified capabilities cannot be created

deliverEvent

public void deliverEvent(Event e)
Parameters:
e

disable

public void disable()

disableEvents

protected final void disableEvents(long eventsToDisable)
Disables the events defined by the specified event mask parameter from being delivered to this component.

Parameters:
eventsToDisable - the event mask defining the event types

dispatchEvent

public final void dispatchEvent(AWTEvent e)
Dispatches an event to this component or one of its sub components. Calls processEvent before returning for 1.1-style events which have been enabled for the Component.

Parameters:
e - the event

doLayout

public void doLayout()
Prompts the layout manager to lay out this component. This is usually called when the component (more specifically, container) is validated.


enable

public void enable()

enable

public void enable(boolean b)
Parameters:
b

enableEvents

protected final void enableEvents(long eventsToEnable)
Enables the events defined by the specified event mask parameter to be delivered to this component.

Event types are automatically enabled when a listener for that event type is added to the component.

This method only needs to be invoked by subclasses of Component which desire to have the specified event types delivered to processEvent regardless of whether or not a listener is registered.

Parameters:
eventsToEnable - the event mask defining the event types

enableInputMethods

public void enableInputMethods(boolean enable)
Enables or disables input method support for this component. If input method support is enabled and the component also processes key events, incoming events are offered to the current input method and will only be processed by the component or dispatched to its listeners if the input method does not consume them. By default, input method support is enabled.

Parameters:
enable - true to enable, false to disable

firePropertyChange

protected void firePropertyChange(String propertyName,
                                  boolean oldValue,
                                  boolean newValue)
Support for reporting bound property changes for boolean properties. This method can be called when a bound property has changed and it will send the appropriate PropertyChangeEvent to any registered PropertyChangeListeners.

Parameters:
propertyName - the property whose value has changed
oldValue - the property's previous value
newValue - the property's new value

firePropertyChange

public void firePropertyChange(String propertyName,
                               byte oldValue,
                               byte newValue)
Reports a bound property change.

Parameters:
propertyName - the programmatic name of the property that was changed
oldValue - the old value of the property (as a byte)
newValue - the new value of the property (as a byte)

firePropertyChange

public void firePropertyChange(String propertyName,
                               char oldValue,
                               char newValue)
Reports a bound property change.

Parameters:
propertyName - the programmatic name of the property that was changed
oldValue - the old value of the property (as a char)
newValue - the new value of the property (as a char)

firePropertyChange

public void firePropertyChange(String propertyName,
                               double oldValue,
                               double newValue)
Reports a bound property change.

Parameters:
propertyName - the programmatic name of the property that was changed
oldValue - the old value of the property (as a double)
newValue - the new value of the property (as a double)

firePropertyChange

public void firePropertyChange(String propertyName,
                               float oldValue,
                               float newValue)
Reports a bound property change.

Parameters:
propertyName - the programmatic name of the property that was changed
oldValue - the old value of the property (as a float)
newValue - the new value of the property (as a float)

firePropertyChange

protected void firePropertyChange(String propertyName,
                                  int oldValue,
                                  int newValue)
Support for reporting bound property changes for integer properties. This method can be called when a bound property has changed and it will send the appropriate PropertyChangeEvent to any registered PropertyChangeListeners.

Parameters:
propertyName - the property whose value has changed
oldValue - the property's previous value
newValue - the property's new value

firePropertyChange

public void firePropertyChange(String propertyName,
                               long oldValue,
                               long newValue)
Reports a bound property change.

Parameters:
propertyName - the programmatic name of the property that was changed
oldValue - the old value of the property (as a long)
newValue - the new value of the property (as a long)

firePropertyChange

protected void firePropertyChange(String propertyName,
                                  Object oldValue,
                                  Object newValue)
Support for reporting bound property changes for Object properties. This method can be called when a bound property has changed and it will send the appropriate PropertyChangeEvent to any registered PropertyChangeListeners.

Parameters:
propertyName - the property whose value has changed
oldValue - the property's previous value
newValue - the property's new value

firePropertyChange

public void firePropertyChange(String propertyName,
                               short oldValue,
                               short newValue)
Reports a bound property change.

Parameters:
propertyName - the programmatic name of the property that was changed
oldValue - the old value of the property (as a short)
newValue - the old value of the property (as a short)

getAccessibleContext

public AccessibleContext getAccessibleContext()
Gets the AccessibleContext associated with this Component. The method implemented by this base class returns null. Classes that extend Component should implement this method to return the AccessibleContext associated with the subclass.

Returns:
the AccessibleContext of this Component

getAlignmentX

public float getAlignmentX()
Returns the alignment along the x axis. This specifies how the component would like to be aligned relative to other components. The value should be a number between 0 and 1 where 0 represents alignment along the origin, 1 is aligned the furthest away from the origin, 0.5 is centered, etc.


getAlignmentY

public float getAlignmentY()
Returns the alignment along the y axis. This specifies how the component would like to be aligned relative to other components. The value should be a number between 0 and 1 where 0 represents alignment along the origin, 1 is aligned the furthest away from the origin, 0.5 is centered, etc.


getBackground

public Color getBackground()
Gets the background color of this component.

Returns:
this component's background color; if this component does not have a background color, the background color of its parent is returned

getBaseline

public int getBaseline(int width,
                       int height)
Returns the baseline. The baseline is measured from the top of the component. This method is primarily meant for LayoutManagers to align components along their baseline. A return value less than 0 indicates this component does not have a reasonable baseline and that LayoutManagers should not align this component on its baseline.

The default implementation returns -1. Subclasses that support baseline should override appropriately. If a value >= 0 is returned, then the component has a valid baseline for any size >= the minimum size and getBaselineResizeBehavior can be used to determine how the baseline changes with size.

Parameters:
width - the width to get the baseline for
height - the height to get the baseline for
Returns:
the baseline or < 0 indicating there is no reasonable baseline

getBaselineResizeBehavior

public Component.BaselineResizeBehavior getBaselineResizeBehavior()
Returns an enum indicating how the baseline of the component changes as the size changes. This method is primarily meant for layout managers and GUI builders.

The default implementation returns BaselineResizeBehavior.OTHER. Subclasses that have a baseline should override appropriately. Subclasses should never return null; if the baseline can not be calculated return BaselineResizeBehavior.OTHER. Callers should first ask for the baseline using getBaseline and if a value >= 0 is returned use this method. It is acceptable for this method to return a value other than BaselineResizeBehavior.OTHER even if getBaseline returns a value less than 0.

Returns:
an enum indicating how the baseline changes as the component size changes

getBounds

public Rectangle getBounds()
Gets the bounds of this component in the form of a Rectangle object. The bounds specify this component's width, height, and location relative to its parent.

Returns:
a rectangle indicating this component's bounds

getBounds

public Rectangle getBounds(Rectangle rv)
Stores the bounds of this component into "return value" rv and return rv. If rv is null a new Rectangle is allocated. This version of getBounds is useful if the caller wants to avoid allocating a new Rectangle object on the heap.

Parameters:
rv - the return value, modified to the components bounds
Returns:
rv

getColorModel

public ColorModel getColorModel()
Gets the instance of ColorModel used to display the component on the output device.

Returns:
the color model used by this component

getComponentAt

public Component getComponentAt(int x,
                                int y)
Determines if this component or one of its immediate subcomponents contains the (xy) location, and if so, returns the containing component. This method only looks one level deep. If the point (xy) is inside a subcomponent that itself has subcomponents, it does not go looking down the subcomponent tree.

The locate method of Component simply returns the component itself if the (xy) coordinate location is inside its bounding box, and null otherwise.

Parameters:
x - the x coordinate
y - the y coordinate
Returns:
the component or subcomponent that contains the (xy) location; null if the location is outside this component

getComponentAt

public Component getComponentAt(Point p)
Returns the component or subcomponent that contains the specified point.

Parameters:
p - the point

getComponentListeners

public synchronized ComponentListener[] getComponentListeners()
Returns an array of all the component listeners registered on this component.

Returns:
all of this comonent's ComponentListeners or an empty array if no component listeners are currently registered

getComponentOrientation

public ComponentOrientation getComponentOrientation()
Retrieves the language-sensitive orientation that is to be used to order the elements or text within this component. LayoutManager and Component subclasses that wish to respect orientation should call this method to get the component's orientation before performing layout or drawing.


getCursor

public Cursor getCursor()
Gets the cursor set in the component. If the component does not have a cursor set, the cursor of its parent is returned. If no cursor is set in the entire hierarchy, Cursor.DEFAULT_CURSOR is returned.


getDropTarget

public synchronized DropTarget getDropTarget()
Gets the DropTarget associated with this Component.


getFocusCycleRootAncestor

public Container getFocusCycleRootAncestor()
Returns the Container which is the focus cycle root of this Component's focus traversal cycle. Each focus traversal cycle has only a single focus cycle root and each Component which is not a Container belongs to only a single focus traversal cycle. Containers which are focus cycle roots belong to two cycles: one rooted at the Container itself, and one rooted at the Container's nearest focus-cycle-root ancestor. For such Containers, this method will return the Container's nearest focus-cycle- root ancestor.

Returns:
this Component's nearest focus-cycle-root ancestor

getFocusListeners

public synchronized FocusListener[] getFocusListeners()
Returns an array of all the focus listeners registered on this component.

Returns:
all of this component's FocusListeners or an empty array if no component listeners are currently registered

getFocusTraversalKeys

public Set getFocusTraversalKeys(int id)
Returns the Set of focus traversal keys for a given traversal operation for this Component. (See setFocusTraversalKeys for a full description of each key.)

If a Set of traversal keys has not been explicitly defined for this Component, then this Component's parent's Set is returned. If no Set has been explicitly defined for any of this Component's ancestors, then the current KeyboardFocusManager's default Set is returned.

Parameters:
id - one of KeyboardFocusManager.FORWARD_TRAVERSAL_KEYS, KeyboardFocusManager.BACKWARD_TRAVERSAL_KEYS, or KeyboardFocusManager.UP_CYCLE_TRAVERSAL_KEYS
Returns:
the Set of AWTKeyStrokes for the specified operation. The Set will be unmodifiable, and may be empty. null will never be returned.

getFocusTraversalKeysEnabled

public boolean getFocusTraversalKeysEnabled()
Returns whether focus traversal keys are enabled for this Component. Components for which focus traversal keys are disabled receive key events for focus traversal keys. Components for which focus traversal keys are enabled do not see these events; instead, the events are automatically converted to traversal operations.

Returns:
whether focus traversal keys are enabled for this Component

getFont

public Font getFont()
Gets the font of this component.

Returns:
this component's font; if a font has not been set for this component, the font of its parent is returned

getFontMetrics

public FontMetrics getFontMetrics(Font font)
Gets the font metrics for the specified font. Warning: Since Font metrics are affected by the {@link java.awt.font.FontRenderContext FontRenderContext} and this method does not provide one, it can return only metrics for the default render context which may not match that used when rendering on the Component if {@link Graphics2D} functionality is being used. Instead metrics can be obtained at rendering time by calling {@link Graphics#getFontMetrics()} or text measurement APIs on the {@link Font Font} class.

Parameters:
font - the font for which font metrics is to be obtained
Returns:
the font metrics for font

getForeground

public Color getForeground()
Gets the foreground color of this component.

Returns:
this component's foreground color; if this component does not have a foreground color, the foreground color of its parent is returned

getGraphics

public Graphics getGraphics()
Creates a graphics context for this component. This method will return null if this component is currently not displayable.

Returns:
a graphics context for this component, or null if it has none

getGraphicsConfiguration

public GraphicsConfiguration getGraphicsConfiguration()
Gets the GraphicsConfiguration associated with this Component. If the Component has not been assigned a specific GraphicsConfiguration, the GraphicsConfiguration of the Component object's top-level container is returned. If the Component has been created, but not yet added to a Container, this method returns null.

Returns:
the GraphicsConfiguration used by this Component or null

getHeight

public int getHeight()
Returns the current height of this component. This method is preferable to writing component.getBounds().height, or component.getSize().height because it doesn't cause any heap allocations.

Returns:
the current height of this component

getHierarchyBoundsListeners

public synchronized HierarchyBoundsListener[] getHierarchyBoundsListeners()
Returns an array of all the hierarchy bounds listeners registered on this component.

Returns:
all of this component's HierarchyBoundsListeners or an empty array if no hierarchy bounds listeners are currently registered

getHierarchyListeners

public synchronized HierarchyListener[] getHierarchyListeners()
Returns an array of all the hierarchy listeners registered on this component.

Returns:
all of this component's HierarchyListeners or an empty array if no hierarchy listeners are currently registered

getIgnoreRepaint

public boolean getIgnoreRepaint()
Returns:
whether or not paint messages received from the operating system should be ignored.

getInputContext

public InputContext getInputContext()
Gets the input context used by this component for handling the communication with input methods when text is entered in this component. By default, the input context used for the parent component is returned. Components may override this to return a private input context.

Returns:
the input context used by this component; null if no context can be determined

getInputMethodListeners

public synchronized InputMethodListener[] getInputMethodListeners()
Returns an array of all the input method listeners registered on this component.

Returns:
all of this component's InputMethodListeners or an empty array if no input method listeners are currently registered

getInputMethodRequests

public InputMethodRequests getInputMethodRequests()
Gets the input method request handler which supports requests from input methods for this component. A component that supports on-the-spot text input must override this method to return an InputMethodRequests instance. At the same time, it also has to handle input method events.

Returns:
the input method request handler for this component, null by default

getKeyListeners

public synchronized KeyListener[] getKeyListeners()
Returns an array of all the key listeners registered on this component.

Returns:
all of this component's KeyListeners or an empty array if no key listeners are currently registered

getListeners

public EventListener[] getListeners(Class listenerType)
Returns an array of all the objects currently registered as FooListeners upon this Component. FooListeners are registered using the addFooListener method.

You can specify the listenerType argument with a class literal, such as FooListener.class. For example, you can query a Component c for its mouse listeners with the following code:

MouseListener[] mls = (MouseListener[])(c.getListeners(MouseListener.class));
If no such listeners exist, this method returns an empty array.

Parameters:
listenerType - the type of listeners requested; this parameter should specify an interface that descends from java.util.EventListener
Returns:
an array of all objects registered as FooListeners on this component, or an empty array if no such listeners have been added

getLocale

public Locale getLocale()
Gets the locale of this component.

Returns:
this component's locale; if this component does not have a locale, the locale of its parent is returned

getLocation

public Point getLocation()
Gets the location of this component in the form of a point specifying the component's top-left corner. The location will be relative to the parent's coordinate space.

Due to the asynchronous nature of native event handling, this method can return outdated values (for instance, after several calls of setLocation() in rapid succession). For this reason, the recommended method of obtaining a component's position is within java.awt.event.ComponentListener.componentMoved(), which is called after the operating system has finished moving the component.

Returns:
an instance of Point representing the top-left corner of the component's bounds in the coordinate space of the component's parent

getLocation

public Point getLocation(Point rv)
Stores the x,y origin of this component into "return value" rv and return rv. If rv is null a new Point is allocated. This version of getLocation is useful if the caller wants to avoid allocating a new Point object on the heap.

Parameters:
rv - the return value, modified to the components location
Returns:
rv

getLocationOnScreen

public Point getLocationOnScreen()
Gets the location of this component in the form of a point specifying the component's top-left corner in the screen's coordinate space.

Returns:
an instance of Point representing the top-left corner of the component's bounds in the coordinate space of the screen

getMaximumSize

public Dimension getMaximumSize()
Gets the maximum size of this component.

Returns:
a dimension object indicating this component's maximum size

getMinimumSize

public Dimension getMinimumSize()
Gets the mininimum size of this component.

Returns:
a dimension object indicating this component's minimum size

getMouseListeners

public synchronized MouseListener[] getMouseListeners()
Returns an array of all the mouse listeners registered on this component.

Returns:
all of this component's MouseListeners or an empty array if no mouse listeners are currently registered

getMouseMotionListeners

public synchronized MouseMotionListener[] getMouseMotionListeners()
Returns an array of all the mouse motion listeners registered on this component.

Returns:
all of this component's MouseMotionListeners or an empty array if no mouse motion listeners are currently registered

getMousePosition

public Point getMousePosition()
                       throws HeadlessException
Returns the position of the mouse pointer in this Component's coordinate space if the Component is directly under the mouse pointer, otherwise returns null. If the Component is not showing on the screen, this method returns null even if the mouse pointer is above the area where the Component would be displayed. If the Component is partially or fully obscured by other Components or native windows, this method returns a non-null value only if the mouse pointer is located above the unobscured part of the Component.

For Containers it returns a non-null value if the mouse is above the Container itself or above any of its descendants. Use {@link Container#getMousePosition(boolean)} if you need to exclude children.

Sometimes the exact mouse coordinates are not important, and the only thing that matters is whether a specific Component is under the mouse pointer. If the return value of this method is null, mouse pointer is not directly above the Component.

Returns:
mouse coordinates relative to this Component, or null
Throws:
HeadlessException - if GraphicsEnvironment.isHeadless() returns true

getMouseWheelListeners

public synchronized MouseWheelListener[] getMouseWheelListeners()
Returns an array of all the mouse wheel listeners registered on this component.

Returns:
all of this component's MouseWheelListeners or an empty array if no mouse wheel listeners are currently registered

getName

public String getName()
Gets the name of the component.

Returns:
this component's name

getParent

public Container getParent()
Gets the parent of this component.

Returns:
the parent container of this component

getPeer

public ComponentPeer getPeer()

getPreferredSize

public Dimension getPreferredSize()
Gets the preferred size of this component.

Returns:
a dimension object indicating this component's preferred size

getPropertyChangeListeners

public synchronized PropertyChangeListener[] getPropertyChangeListeners()
Returns an array of all the property change listeners registered on this component.

Returns:
all of this component's PropertyChangeListeners or an empty array if no property change listeners are currently registered

getPropertyChangeListeners

public synchronized PropertyChangeListener[] getPropertyChangeListeners(String propertyName)
Returns an array of all the listeners which have been associated with the named property.

Parameters:
propertyName
Returns:
all of the PropertyChangeListeners associated with the named property; if no such listeners have been added or if propertyName is null, an empty array is returned

getSize

public Dimension getSize()
Returns the size of this component in the form of a Dimension object. The height field of the Dimension object contains this component's height, and the width field of the Dimension object contains this component's width.

Returns:
a Dimension object that indicates the size of this component

getSize

public Dimension getSize(Dimension rv)
Stores the width/height of this component into "return value" rv and return rv. If rv is null a new Dimension object is allocated. This version of getSize is useful if the caller wants to avoid allocating a new Dimension object on the heap.

Parameters:
rv - the return value, modified to the components size
Returns:
rv

getToolkit

public Toolkit getToolkit()
Gets the toolkit of this component. Note that the frame that contains a component controls which toolkit is used by that component. Therefore if the component is moved from one frame to another, the toolkit it uses may change.

Returns:
the toolkit of this component

getTreeLock

public final Object getTreeLock()
Gets this component's locking object (the object that owns the thread sychronization monitor) for AWT component-tree and layout operations.

Returns:
this component's locking object

getWidth

public int getWidth()
Returns the current width of this component. This method is preferable to writing component.getBounds().width, or component.getSize().width because it doesn't cause any heap allocations.

Returns:
the current width of this component

getX

public int getX()
Returns the current x coordinate of the components origin. This method is preferable to writing component.getBounds().x, or component.getLocation().x because it doesn't cause any heap allocations.

Returns:
the current x coordinate of the components origin

getY

public int getY()
Returns the current y coordinate of the components origin. This method is preferable to writing component.getBounds().y, or component.getLocation().y because it doesn't cause any heap allocations.

Returns:
the current y coordinate of the components origin

gotFocus

public boolean gotFocus(Event evt,
                        Object what)
Parameters:
evt
what

handleEvent

public boolean handleEvent(Event evt)
Parameters:
evt

hasFocus

public boolean hasFocus()
Returns true if this Component is the focus owner. This method is obsolete, and has been replaced by isFocusOwner().

Returns:
true if this Component is the focus owner; false otherwise

hide

public void hide()

imageUpdate

public boolean imageUpdate(Image img,
                           int infoflags,
                           int x,
                           int y,
                           int w,
                           int h)
Repaints the component when the image has changed. This imageUpdate method of an ImageObserver is called when more information about an image which had been previously requested using an asynchronous routine such as the drawImage method of Graphics becomes available. See the definition of imageUpdate for more information on this method and its arguments.

The imageUpdate method of Component incrementally draws an image on the component as more of the bits of the image are available.

If the system property awt.image.incrementaldraw is missing or has the value true, the image is incrementally drawn. If the system property has any other value, then the image is not drawn until it has been completely loaded.

Also, if incremental drawing is in effect, the value of the system property awt.image.redrawrate is interpreted as an integer to give the maximum redraw rate, in milliseconds. If the system property is missing or cannot be interpreted as an integer, the redraw rate is once every 100ms.

The interpretation of the x, y, width, and height arguments depends on the value of the infoflags argument.

Parameters:
img - the image being observed
infoflags - see imageUpdate for more information
x - the x coordinate
y - the y coordinate
w - the width
h - the height
Returns:
false if the infoflags indicate that the image is completely loaded; true otherwise.

inside

public boolean inside(int x,
                      int y)
Parameters:
x
y

invalidate

public void invalidate()
Invalidates this component. This component and all parents above it are marked as needing to be laid out. This method can be called often, so it needs to execute quickly.


isBackgroundSet

public boolean isBackgroundSet()
Returns whether the background color has been explicitly set for this Component. If this method returns false, this Component is inheriting its background color from an ancestor.

Returns:
true if the background color has been explicitly set for this Component; false otherwise.

isCursorSet

public boolean isCursorSet()
Returns whether the cursor has been explicitly set for this Component. If this method returns false, this Component is inheriting its cursor from an ancestor.

Returns:
true if the cursor has been explicitly set for this Component; false otherwise.

isDisplayable

public boolean isDisplayable()
Determines whether this component is displayable. A component is displayable when it is connected to a native screen resource.

A component is made displayable either when it is added to a displayable containment hierarchy or when its containment hierarchy is made displayable. A containment hierarchy is made displayable when its ancestor window is either packed or made visible.

A component is made undisplayable either when it is removed from a displayable containment hierarchy or when its containment hierarchy is made undisplayable. A containment hierarchy is made undisplayable when its ancestor window is disposed.

Returns:
true if the component is displayable, false otherwise

isDoubleBuffered

public boolean isDoubleBuffered()
Returns true if this component is painted to an offscreen image ("buffer") that's copied to the screen later. Component subclasses that support double buffering should override this method to return true if double buffering is enabled.

Returns:
false by default

isEnabled

public boolean isEnabled()
Determines whether this component is enabled. An enabled component can respond to user input and generate events. Components are enabled initially by default. A component may be enabled or disabled by calling its setEnabled method.

Returns:
true if the component is enabled, false otherwise

isFocusable

public boolean isFocusable()
Returns whether this Component can be focused.

Returns:
true if this Component is focusable; false otherwise.

isFocusCycleRoot

public boolean isFocusCycleRoot(Container container)
Returns whether the specified Container is the focus cycle root of this Component's focus traversal cycle. Each focus traversal cycle has only a single focus cycle root and each Component which is not a Container belongs to only a single focus traversal cycle.

Parameters:
container - the Container to be tested
Returns:
true if the specified Container is a focus-cycle- root of this Component; false otherwise

isFocusOwner

public boolean isFocusOwner()
Returns true if this Component is the focus owner.

Returns:
true if this Component is the focus owner; false otherwise

isFocusTraversable

public boolean isFocusTraversable()
Returns whether this Component can become the focus owner.

Returns:
true if this Component is focusable; false otherwise

isFontSet

public boolean isFontSet()
Returns whether the font has been explicitly set for this Component. If this method returns false, this Component is inheriting its font from an ancestor.

Returns:
true if the font has been explicitly set for this Component; false otherwise.

isForegroundSet

public boolean isForegroundSet()
Returns whether the foreground color has been explicitly set for this Component. If this method returns false, this Component is inheriting its foreground color from an ancestor.

Returns:
true if the foreground color has been explicitly set for this Component; false otherwise.

isLightweight

public boolean isLightweight()
A lightweight component doesn't have a native toolkit peer. Subclasses of Component and Container, other than the ones defined in this package like Button or Scrollbar, are lightweight. All of the Swing components are lightweights.

This method will always return false if this component is not displayable because it is impossible to determine the weight of an undisplayable component.

Returns:
true if this component has a lightweight peer; false if it has a native peer or no peer

isMaximumSizeSet

public boolean isMaximumSizeSet()
Returns true if the maximum size has been set to a non-null value otherwise returns false.

Returns:
true if maximumSize is non-null, false otherwise

isMinimumSizeSet

public boolean isMinimumSizeSet()
Returns whether or not setMinimumSize has been invoked with a non-null value.

Returns:
true if setMinimumSize has been invoked with a non-null value.

isOpaque

public boolean isOpaque()
Returns true if this component is completely opaque, returns false by default.

An opaque component paints every pixel within its rectangular region. A non-opaque component paints only some of its pixels, allowing the pixels underneath it to "show through". A component that does not fully paint its pixels therefore provides a degree of transparency. Only lightweight components can be transparent.

Subclasses that guarantee to always completely paint their contents should override this method and return true. All of the "heavyweight" AWT components are opaque.

Returns:
true if this component is completely opaque

isPreferredSizeSet

public boolean isPreferredSizeSet()
Returns true if the preferred size has been set to a non-null value otherwise returns false.

Returns:
true if setPreferredSize has been invoked with a non-null value.

isShowing

public boolean isShowing()
Determines whether this component is showing on screen. This means that the component must be visible, and it must be in a container that is visible and showing.

Note: sometimes there is no way to detect whether the {@code Component} is actually visible to the user. This can happen when:

Returns:
true if the component is showing, false otherwise

isValid

public boolean isValid()
Determines whether this component is valid. A component is valid when it is correctly sized and positioned within its parent container and all its children are also valid. In order to account for peers' size requirements, components are invalidated before they are first shown on the screen. By the time the parent container is fully realized, all its components will be valid.

Returns:
true if the component is valid, false otherwise

isVisible

public boolean isVisible()
Determines whether this component should be visible when its parent is visible. Components are initially visible, with the exception of top level components such as Frame objects.

Returns:
true if the component is visible, false otherwise

keyDown

public boolean keyDown(Event evt,
                       int key)
Parameters:
evt
key

keyUp

public boolean keyUp(Event evt,
                     int key)
Parameters:
evt
key

layout

public void layout()

list

public void list()
Prints a listing of this component to the standard system output stream System.out.


list

public void list(PrintStream out)
Prints a listing of this component to the specified output stream.

Parameters:
out - a print stream

list

public void list(PrintStream out,
                 int indent)
Prints out a list, starting at the specified indentation, to the specified print stream.

Parameters:
out - a print stream
indent - number of spaces to indent

list

public void list(PrintWriter out)
Prints a listing to the specified print writer.

Parameters:
out - the print writer to print to

list

public void list(PrintWriter out,
                 int indent)
Prints out a list, starting at the specified indentation, to the specified print writer.

Parameters:
out - the print writer to print to
indent - the number of spaces to indent

locate

public Component locate(int x,
                        int y)
Parameters:
x
y

location

public Point location()

lostFocus

public boolean lostFocus(Event evt,
                         Object what)
Parameters:
evt
what

minimumSize

public Dimension minimumSize()

mouseDown

public boolean mouseDown(Event evt,
                         int x,
                         int y)
Parameters:
evt
x
y

mouseDrag

public boolean mouseDrag(Event evt,
                         int x,
                         int y)
Parameters:
evt
x
y

mouseEnter

public boolean mouseEnter(Event evt,
                          int x,
                          int y)
Parameters:
evt
x
y

mouseExit

public boolean mouseExit(Event evt,
                         int x,
                         int y)
Parameters:
evt
x
y

mouseMove

public boolean mouseMove(Event evt,
                         int x,
                         int y)
Parameters:
evt
x
y

mouseUp

public boolean mouseUp(Event evt,
                       int x,
                       int y)
Parameters:
evt
x
y

move

public void move(int x,
                 int y)
Parameters:
x
y

nextFocus

public void nextFocus()

paint

public void paint(Graphics g)
Paints this component.

This method is called when the contents of the component should be painted; such as when the component is first being shown or is damaged and in need of repair. The clip rectangle in the Graphics parameter is set to the area which needs to be painted. Subclasses of Component that override this method need not call super.paint(g).

For performance reasons, Components with zero width or height aren't considered to need painting when they are first shown, and also aren't considered to need repair.

Note: For more information on the paint mechanisms utilitized by AWT and Swing, including information on how to write the most efficient painting code, see Painting in AWT and Swing.

Parameters:
g - the graphics context to use for painting

paintAll

public void paintAll(Graphics g)
Paints this component and all of its subcomponents.

The origin of the graphics context, its (00) coordinate point, is the top-left corner of this component. The clipping region of the graphics context is the bounding rectangle of this component.

Parameters:
g - the graphics context to use for painting

paramString

protected String paramString()
Returns a string representing the state of this component. This method is intended to be used only for debugging purposes, and the content and format of the returned string may vary between implementations. The returned string may be empty but may not be null.

Returns:
a string representation of this component's state

postEvent

public boolean postEvent(Event e)
Parameters:
e

preferredSize

public Dimension preferredSize()

prepareImage

public boolean prepareImage(Image image,
                            ImageObserver observer)
Prepares an image for rendering on this component. The image data is downloaded asynchronously in another thread and the appropriate screen representation of the image is generated.

Parameters:
image - the Image for which to prepare a screen representation
observer - the ImageObserver object to be notified as the image is being prepared
Returns:
true if the image has already been fully prepared; false otherwise

prepareImage

public boolean prepareImage(Image image,
                            int width,
                            int height,
                            ImageObserver observer)
Prepares an image for rendering on this component at the specified width and height.

The image data is downloaded asynchronously in another thread, and an appropriately scaled screen representation of the image is generated.

Parameters:
image - the instance of Image for which to prepare a screen representation
width - the width of the desired screen representation
height - the height of the desired screen representation
observer - the ImageObserver object to be notified as the image is being prepared
Returns:
true if the image has already been fully prepared; false otherwise

print

public void print(Graphics g)
Prints this component. Applications should override this method for components that must do special processing before being printed or should be printed differently than they are painted.

The default implementation of this method calls the paint method.

The origin of the graphics context, its (00) coordinate point, is the top-left corner of this component. The clipping region of the graphics context is the bounding rectangle of this component.

Parameters:
g - the graphics context to use for printing

printAll

public void printAll(Graphics g)
Prints this component and all of its subcomponents.

The origin of the graphics context, its (00) coordinate point, is the top-left corner of this component. The clipping region of the graphics context is the bounding rectangle of this component.

Parameters:
g - the graphics context to use for printing

processComponentEvent

protected void processComponentEvent(ComponentEvent e)
Processes component events occurring on this component by dispatching them to any registered ComponentListener objects.

This method is not called unless component events are enabled for this component. Component events are enabled when one of the following occurs:

Note that if the event parameter is null the behavior is unspecified and may result in an exception.

Parameters:
e - the component event

processEvent

protected void processEvent(AWTEvent e)
Processes events occurring on this component. By default this method calls the appropriate process<event type>Event method for the given class of event.

Note that if the event parameter is null the behavior is unspecified and may result in an exception.

Parameters:
e - the event

processFocusEvent

protected void processFocusEvent(FocusEvent e)
Processes focus events occurring on this component by dispatching them to any registered FocusListener objects.

This method is not called unless focus events are enabled for this component. Focus events are enabled when one of the following occurs:

If focus events are enabled for a Component, the current KeyboardFocusManager determines whether or not a focus event should be dispatched to registered FocusListener objects. If the events are to be dispatched, the KeyboardFocusManager calls the Component's dispatchEvent method, which results in a call to the Component's processFocusEvent method.

If focus events are enabled for a Component, calling the Component's dispatchEvent method with a FocusEvent as the argument will result in a call to the Component's processFocusEvent method regardless of the current KeyboardFocusManager.

Note that if the event parameter is null the behavior is unspecified and may result in an exception.

Parameters:
e - the focus event

processHierarchyBoundsEvent

protected void processHierarchyBoundsEvent(HierarchyEvent e)
Processes hierarchy bounds events occurring on this component by dispatching them to any registered HierarchyBoundsListener objects.

This method is not called unless hierarchy bounds events are enabled for this component. Hierarchy bounds events are enabled when one of the following occurs:

Note that if the event parameter is null the behavior is unspecified and may result in an exception.

Parameters:
e - the hierarchy event

processHierarchyEvent

protected void processHierarchyEvent(HierarchyEvent e)
Processes hierarchy events occurring on this component by dispatching them to any registered HierarchyListener objects.

This method is not called unless hierarchy events are enabled for this component. Hierarchy events are enabled when one of the following occurs:

Note that if the event parameter is null the behavior is unspecified and may result in an exception.

Parameters:
e - the hierarchy event

processInputMethodEvent

protected void processInputMethodEvent(InputMethodEvent e)
Processes input method events occurring on this component by dispatching them to any registered InputMethodListener objects.

This method is not called unless input method events are enabled for this component. Input method events are enabled when one of the following occurs:

Note that if the event parameter is null the behavior is unspecified and may result in an exception.

Parameters:
e - the input method event

processKeyEvent

protected void processKeyEvent(KeyEvent e)
Processes key events occurring on this component by dispatching them to any registered KeyListener objects.

This method is not called unless key events are enabled for this component. Key events are enabled when one of the following occurs:

If key events are enabled for a Component, the current KeyboardFocusManager determines whether or not a key event should be dispatched to registered KeyListener objects. The DefaultKeyboardFocusManager will not dispatch key events to a Component that is not the focus owner or is not showing.

As of J2SE 1.4, KeyEvents are redirected to the focus owner. Please see the Focus Specification for further information.

Calling a Component's dispatchEvent method with a KeyEvent as the argument will result in a call to the Component's processKeyEvent method regardless of the current KeyboardFocusManager as long as the component is showing, focused, and enabled, and key events are enabled on it.

If the event parameter is null the behavior is unspecified and may result in an exception.

Parameters:
e - the key event

processMouseEvent

protected void processMouseEvent(MouseEvent e)
Processes mouse events occurring on this component by dispatching them to any registered MouseListener objects.

This method is not called unless mouse events are enabled for this component. Mouse events are enabled when one of the following occurs:

Note that if the event parameter is null the behavior is unspecified and may result in an exception.

Parameters:
e - the mouse event

processMouseMotionEvent

protected void processMouseMotionEvent(MouseEvent e)
Processes mouse motion events occurring on this component by dispatching them to any registered MouseMotionListener objects.

This method is not called unless mouse motion events are enabled for this component. Mouse motion events are enabled when one of the following occurs:

Note that if the event parameter is null the behavior is unspecified and may result in an exception.

Parameters:
e - the mouse motion event

processMouseWheelEvent

protected void processMouseWheelEvent(MouseWheelEvent e)
Processes mouse wheel events occurring on this component by dispatching them to any registered MouseWheelListener objects.

This method is not called unless mouse wheel events are enabled for this component. Mouse wheel events are enabled when one of the following occurs:

For information on how mouse wheel events are dispatched, see the class description for {@link MouseWheelEvent}.

Note that if the event parameter is null the behavior is unspecified and may result in an exception.

Parameters:
e - the mouse wheel event

remove

public synchronized void remove(MenuComponent popup)
Removes the specified popup menu from the component.

Parameters:
popup - the popup menu to be removed

removeComponentListener

public synchronized void removeComponentListener(ComponentListener l)
Removes the specified component listener so that it no longer receives component events from this component. This method performs no function, nor does it throw an exception, if the listener specified by the argument was not previously added to this component. If listener l is null, no exception is thrown and no action is performed.

Refer to AWT Threading Issues for details on AWT's threading model.

Parameters:
l - the component listener

removeFocusListener

public synchronized void removeFocusListener(FocusListener l)
Removes the specified focus listener so that it no longer receives focus events from this component. This method performs no function, nor does it throw an exception, if the listener specified by the argument was not previously added to this component. If listener l is null, no exception is thrown and no action is performed.

Refer to AWT Threading Issues for details on AWT's threading model.

Parameters:
l - the focus listener

removeHierarchyBoundsListener

public void removeHierarchyBoundsListener(HierarchyBoundsListener l)
Removes the specified hierarchy bounds listener so that it no longer receives hierarchy bounds events from this component. This method performs no function, nor does it throw an exception, if the listener specified by the argument was not previously added to this component. If listener l is null, no exception is thrown and no action is performed.

Refer to AWT Threading Issues for details on AWT's threading model.

Parameters:
l - the hierarchy bounds listener

removeHierarchyListener

public void removeHierarchyListener(HierarchyListener l)
Removes the specified hierarchy listener so that it no longer receives hierarchy changed events from this component. This method performs no function, nor does it throw an exception, if the listener specified by the argument was not previously added to this component. If listener l is null, no exception is thrown and no action is performed.

Refer to AWT Threading Issues for details on AWT's threading model.

Parameters:
l - the hierarchy listener

removeInputMethodListener

public synchronized void removeInputMethodListener(InputMethodListener l)
Removes the specified input method listener so that it no longer receives input method events from this component. This method performs no function, nor does it throw an exception, if the listener specified by the argument was not previously added to this component. If listener l is null, no exception is thrown and no action is performed.

Refer to AWT Threading Issues for details on AWT's threading model.

Parameters:
l - the input method listener

removeKeyListener

public synchronized void removeKeyListener(KeyListener l)
Removes the specified key listener so that it no longer receives key events from this component. This method performs no function, nor does it throw an exception, if the listener specified by the argument was not previously added to this component. If listener l is null, no exception is thrown and no action is performed.

Refer to AWT Threading Issues for details on AWT's threading model.

Parameters:
l - the key listener

removeMouseListener

public synchronized void removeMouseListener(MouseListener l)
Removes the specified mouse listener so that it no longer receives mouse events from this component. This method performs no function, nor does it throw an exception, if the listener specified by the argument was not previously added to this component. If listener l is null, no exception is thrown and no action is performed.

Refer to AWT Threading Issues for details on AWT's threading model.

Parameters:
l - the mouse listener

removeMouseMotionListener

public synchronized void removeMouseMotionListener(MouseMotionListener l)
Removes the specified mouse motion listener so that it no longer receives mouse motion events from this component. This method performs no function, nor does it throw an exception, if the listener specified by the argument was not previously added to this component. If listener l is null, no exception is thrown and no action is performed.

Refer to AWT Threading Issues for details on AWT's threading model.

Parameters:
l - the mouse motion listener

removeMouseWheelListener

public synchronized void removeMouseWheelListener(MouseWheelListener l)
Removes the specified mouse wheel listener so that it no longer receives mouse wheel events from this component. This method performs no function, nor does it throw an exception, if the listener specified by the argument was not previously added to this component. If l is null, no exception is thrown and no action is performed.

Refer to AWT Threading Issues for details on AWT's threading model.

Parameters:
l - the mouse wheel listener.

removeNotify

public void removeNotify()
Makes this Component undisplayable by destroying it native screen resource.

This method is called by the toolkit internally and should not be called directly by programs. Code overriding this method should call super.removeNotify as the first line of the overriding method.


removePropertyChangeListener

public synchronized void removePropertyChangeListener(PropertyChangeListener listener)
Removes a PropertyChangeListener from the listener list. This method should be used to remove PropertyChangeListeners that were registered for all bound properties of this class.

If listener is null, no exception is thrown and no action is performed.

Parameters:
listener - the PropertyChangeListener to be removed

removePropertyChangeListener

public synchronized void removePropertyChangeListener(String propertyName,
                                                      PropertyChangeListener listener)
Removes a PropertyChangeListener from the listener list for a specific property. This method should be used to remove PropertyChangeListeners that were registered for a specific bound property.

If propertyName or listener is null, no exception is thrown and no action is taken.

Parameters:
propertyName - a valid property name
listener - the PropertyChangeListener to be removed

repaint

public void repaint()
Repaints this component.

If this component is a lightweight component, this method causes a call to this component's paint method as soon as possible. Otherwise, this method causes a call to this component's update method as soon as possible.

Note: For more information on the paint mechanisms utilitized by AWT and Swing, including information on how to write the most efficient painting code, see Painting in AWT and Swing.


repaint

public void repaint(int x,
                    int y,
                    int width,
                    int height)
Repaints the specified rectangle of this component.

If this component is a lightweight component, this method causes a call to this component's paint method as soon as possible. Otherwise, this method causes a call to this component's update method as soon as possible.

Note: For more information on the paint mechanisms utilitized by AWT and Swing, including information on how to write the most efficient painting code, see Painting in AWT and Swing.

Parameters:
x - the x coordinate
y - the y coordinate
width - the width
height - the height

repaint

public void repaint(long tm)
Repaints the component. If this component is a lightweight component, this results in a call to paint within tm milliseconds.

Note: For more information on the paint mechanisms utilitized by AWT and Swing, including information on how to write the most efficient painting code, see Painting in AWT and Swing.

Parameters:
tm - maximum time in milliseconds before update

repaint

public void repaint(long tm,
                    int x,
                    int y,
                    int width,
                    int height)
Repaints the specified rectangle of this component within tm milliseconds.

If this component is a lightweight component, this method causes a call to this component's paint method. Otherwise, this method causes a call to this component's update method.

Note: For more information on the paint mechanisms utilitized by AWT and Swing, including information on how to write the most efficient painting code, see Painting in AWT and Swing.

Parameters:
tm - maximum time in milliseconds before update
x - the x coordinate
y - the y coordinate
width - the width
height - the height

requestFocus

public void requestFocus()
Requests that this Component get the input focus, and that this Component's top-level ancestor become the focused Window. This component must be displayable, focusable, visible and all of its ancestors (with the exception of the top-level Window) must be visible for the request to be granted. Every effort will be made to honor the request; however, in some cases it may be impossible to do so. Developers must never assume that this Component is the focus owner until this Component receives a FOCUS_GAINED event. If this request is denied because this Component's top-level Window cannot become the focused Window, the request will be remembered and will be granted when the Window is later focused by the user.

This method cannot be used to set the focus owner to no Component at all. Use KeyboardFocusManager.clearGlobalFocusOwner() instead.

Because the focus behavior of this method is platform-dependent, developers are strongly encouraged to use requestFocusInWindow when possible.

Note: Not all focus transfers result from invoking this method. As such, a component may receive focus without this or any of the other {@code requestFocus} methods of {@code Component} being invoked.


requestFocus

protected boolean requestFocus(boolean temporary)
Requests that this Component get the input focus, and that this Component's top-level ancestor become the focused Window. This component must be displayable, focusable, visible and all of its ancestors (with the exception of the top-level Window) must be visible for the request to be granted. Every effort will be made to honor the request; however, in some cases it may be impossible to do so. Developers must never assume that this component is the focus owner until this component receives a FOCUS_GAINED event. If this request is denied because this component's top-level window cannot become the focused window, the request will be remembered and will be granted when the window is later focused by the user.

This method returns a boolean value. If false is returned, the request is guaranteed to fail. If true is returned, the request will succeed unless it is vetoed, or an extraordinary event, such as disposal of the component's peer, occurs before the request can be granted by the native windowing system. Again, while a return value of true indicates that the request is likely to succeed, developers must never assume that this component is the focus owner until this component receives a FOCUS_GAINED event.

This method cannot be used to set the focus owner to no component at all. Use KeyboardFocusManager.clearGlobalFocusOwner instead.

Because the focus behavior of this method is platform-dependent, developers are strongly encouraged to use requestFocusInWindow when possible.

Every effort will be made to ensure that FocusEvents generated as a result of this request will have the specified temporary value. However, because specifying an arbitrary temporary state may not be implementable on all native windowing systems, correct behavior for this method can be guaranteed only for lightweight Components. This method is not intended for general use, but exists instead as a hook for lightweight component libraries, such as Swing.

Note: Not all focus transfers result from invoking this method. As such, a component may receive focus without this or any of the other {@code requestFocus} methods of {@code Component} being invoked.

Parameters:
temporary - true if the focus change is temporary, such as when the window loses the focus; for more information on temporary focus changes see the Focus Specification
Returns:
false if the focus change request is guaranteed to fail; true if it is likely to succeed

requestFocusInWindow

public boolean requestFocusInWindow()
Requests that this Component get the input focus, if this Component's top-level ancestor is already the focused Window. This component must be displayable, focusable, visible and all of its ancestors (with the exception of the top-level Window) must be visible for the request to be granted. Every effort will be made to honor the request; however, in some cases it may be impossible to do so. Developers must never assume that this Component is the focus owner until this Component receives a FOCUS_GAINED event.

This method returns a boolean value. If false is returned, the request is guaranteed to fail. If true is returned, the request will succeed unless it is vetoed, or an extraordinary event, such as disposal of the Component's peer, occurs before the request can be granted by the native windowing system. Again, while a return value of true indicates that the request is likely to succeed, developers must never assume that this Component is the focus owner until this Component receives a FOCUS_GAINED event.

This method cannot be used to set the focus owner to no Component at all. Use KeyboardFocusManager.clearGlobalFocusOwner() instead.

The focus behavior of this method can be implemented uniformly across platforms, and thus developers are strongly encouraged to use this method over requestFocus when possible. Code which relies on requestFocus may exhibit different focus behavior on different platforms.

Note: Not all focus transfers result from invoking this method. As such, a component may receive focus without this or any of the other {@code requestFocus} methods of {@code Component} being invoked.

Returns:
false if the focus change request is guaranteed to fail; true if it is likely to succeed

requestFocusInWindow

protected boolean requestFocusInWindow(boolean temporary)
Requests that this Component get the input focus, if this Component's top-level ancestor is already the focused Window. This component must be displayable, focusable, visible and all of its ancestors (with the exception of the top-level Window) must be visible for the request to be granted. Every effort will be made to honor the request; however, in some cases it may be impossible to do so. Developers must never assume that this component is the focus owner until this component receives a FOCUS_GAINED event.

This method returns a boolean value. If false is returned, the request is guaranteed to fail. If true is returned, the request will succeed unless it is vetoed, or an extraordinary event, such as disposal of the component's peer, occurs before the request can be granted by the native windowing system. Again, while a return value of true indicates that the request is likely to succeed, developers must never assume that this component is the focus owner until this component receives a FOCUS_GAINED event.

This method cannot be used to set the focus owner to no component at all. Use KeyboardFocusManager.clearGlobalFocusOwner instead.

The focus behavior of this method can be implemented uniformly across platforms, and thus developers are strongly encouraged to use this method over requestFocus when possible. Code which relies on requestFocus may exhibit different focus behavior on different platforms.

Every effort will be made to ensure that FocusEvents generated as a result of this request will have the specified temporary value. However, because specifying an arbitrary temporary state may not be implementable on all native windowing systems, correct behavior for this method can be guaranteed only for lightweight components. This method is not intended for general use, but exists instead as a hook for lightweight component libraries, such as Swing.

Note: Not all focus transfers result from invoking this method. As such, a component may receive focus without this or any of the other {@code requestFocus} methods of {@code Component} being invoked.

Parameters:
temporary - true if the focus change is temporary, such as when the window loses the focus; for more information on temporary focus changes see the Focus Specification
Returns:
false if the focus change request is guaranteed to fail; true if it is likely to succeed

reshape

public void reshape(int x,
                    int y,
                    int width,
                    int height)
Parameters:
x
y
width
height

resize

public void resize(Dimension d)
Parameters:
d

resize

public void resize(int width,
                   int height)
Parameters:
width
height

setBackground

public void setBackground(Color c)
Sets the background color of this component.

The background color affects each component differently and the parts of the component that are affected by the background color may differ between operating systems.

Parameters:
c - the color to become this component's color; if this parameter is null, then this component will inherit the background color of its parent

setBounds

public void setBounds(int x,
                      int y,
                      int width,
                      int height)
Moves and resizes this component. The new location of the top-left corner is specified by x and y, and the new size is specified by width and height.

Parameters:
x - the new x-coordinate of this component
y - the new y-coordinate of this component
width - the new width of this component
height - the new height of this component

setBounds

public void setBounds(Rectangle r)
Moves and resizes this component to conform to the new bounding rectangle r. This component's new position is specified by r.x and r.y, and its new size is specified by r.width and r.height

Parameters:
r - the new bounding rectangle for this component

setComponentOrientation

public void setComponentOrientation(ComponentOrientation o)
Sets the language-sensitive orientation that is to be used to order the elements or text within this component. Language-sensitive LayoutManager and Component subclasses will use this property to determine how to lay out and draw components.

At construction time, a component's orientation is set to ComponentOrientation.UNKNOWN, indicating that it has not been specified explicitly. The UNKNOWN orientation behaves the same as ComponentOrientation.LEFT_TO_RIGHT.

To set the orientation of a single component, use this method. To set the orientation of an entire component hierarchy, use {@link #applyComponentOrientation applyComponentOrientation}.

Parameters:
o

setCursor

public void setCursor(Cursor cursor)
Sets the cursor image to the specified cursor. This cursor image is displayed when the contains method for this component returns true for the current cursor location, and this Component is visible, displayable, and enabled. Setting the cursor of a Container causes that cursor to be displayed within all of the container's subcomponents, except for those that have a non-null cursor.

The method may have no visual effect if the Java platform implementation and/or the native system do not support changing the mouse cursor shape.

Parameters:
cursor - One of the constants defined by the Cursor class; if this parameter is null then this component will inherit the cursor of its parent

setDropTarget

public synchronized void setDropTarget(DropTarget dt)
Associate a DropTarget with this component. The Component will receive drops only if it is enabled.

Parameters:
dt - The DropTarget

setEnabled

public void setEnabled(boolean b)
Enables or disables this component, depending on the value of the parameter b. An enabled component can respond to user input and generate events. Components are enabled initially by default.

Note: Disabling a lightweight component does not prevent it from receiving MouseEvents.

Note: Disabling a heavyweight container prevents all components in this container from receiving any input events. But disabling a lightweight container affects only this container.

Parameters:
b - If true, this component is enabled; otherwise this component is disabled

setFocusable

public void setFocusable(boolean focusable)
Sets the focusable state of this Component to the specified value. This value overrides the Component's default focusability.

Parameters:
focusable - indicates whether this Component is focusable

setFocusTraversalKeys

public void setFocusTraversalKeys(int id,
                                  Set keystrokes)
Sets the focus traversal keys for a given traversal operation for this Component.

The default values for a Component's focus traversal keys are implementation-dependent. Sun recommends that all implementations for a particular native platform use the same default values. The recommendations for Windows and Unix are listed below. These recommendations are used in the Sun AWT implementations.

Identifier Meaning Default
KeyboardFocusManager.FORWARD_TRAVERSAL_KEYS Normal forward keyboard traversal TAB on KEY_PRESSED, CTRL-TAB on KEY_PRESSED
KeyboardFocusManager.BACKWARD_TRAVERSAL_KEYS Normal reverse keyboard traversal SHIFT-TAB on KEY_PRESSED, CTRL-SHIFT-TAB on KEY_PRESSED
KeyboardFocusManager.UP_CYCLE_TRAVERSAL_KEYS Go up one focus traversal cycle none
To disable a traversal key, use an empty Set; Collections.EMPTY_SET is recommended.

Using the AWTKeyStroke API, client code can specify on which of two specific KeyEvents, KEY_PRESSED or KEY_RELEASED, the focus traversal operation will occur. Regardless of which KeyEvent is specified, however, all KeyEvents related to the focus traversal key, including the associated KEY_TYPED event, will be consumed, and will not be dispatched to any Component. It is a runtime error to specify a KEY_TYPED event as mapping to a focus traversal operation, or to map the same event to multiple default focus traversal operations.

If a value of null is specified for the Set, this Component inherits the Set from its parent. If all ancestors of this Component have null specified for the Set, then the current KeyboardFocusManager's default Set is used.

Parameters:
id - one of KeyboardFocusManager.FORWARD_TRAVERSAL_KEYS, KeyboardFocusManager.BACKWARD_TRAVERSAL_KEYS, or KeyboardFocusManager.UP_CYCLE_TRAVERSAL_KEYS
keystrokes - the Set of AWTKeyStroke for the specified operation

setFocusTraversalKeysEnabled

public void setFocusTraversalKeysEnabled(boolean focusTraversalKeysEnabled)
Sets whether focus traversal keys are enabled for this Component. Components for which focus traversal keys are disabled receive key events for focus traversal keys. Components for which focus traversal keys are enabled do not see these events; instead, the events are automatically converted to traversal operations.

Parameters:
focusTraversalKeysEnabled - whether focus traversal keys are enabled for this Component

setFont

public void setFont(Font f)
Sets the font of this component.

Parameters:
f - the font to become this component's font; if this parameter is null then this component will inherit the font of its parent

setForeground

public void setForeground(Color c)
Sets the foreground color of this component.

Parameters:
c - the color to become this component's foreground color; if this parameter is null then this component will inherit the foreground color of its parent

setIgnoreRepaint

public void setIgnoreRepaint(boolean ignoreRepaint)
Sets whether or not paint messages received from the operating system should be ignored. This does not affect paint events generated in software by the AWT, unless they are an immediate response to an OS-level paint message.

This is useful, for example, if running under full-screen mode and better performance is desired, or if page-flipping is used as the buffer strategy.

Parameters:
ignoreRepaint

setLocale

public void setLocale(Locale l)
Sets the locale of this component. This is a bound property.

Parameters:
l - the locale to become this component's locale

setLocation

public void setLocation(int x,
                        int y)
Moves this component to a new location. The top-left corner of the new location is specified by the x and y parameters in the coordinate space of this component's parent.

Parameters:
x - the x-coordinate of the new location's top-left corner in the parent's coordinate space
y - the y-coordinate of the new location's top-left corner in the parent's coordinate space

setLocation

public void setLocation(Point p)
Moves this component to a new location. The top-left corner of the new location is specified by point p. Point p is given in the parent's coordinate space.

Parameters:
p - the point defining the top-left corner of the new location, given in the coordinate space of this component's parent

setMaximumSize

public void setMaximumSize(Dimension maximumSize)
Sets the maximum size of this component to a constant value. Subsequent calls to getMaximumSize will always return this value. Setting the maximum size to null restores the default behavior.

Parameters:
maximumSize - a Dimension containing the desired maximum allowable size

setMinimumSize

public void setMinimumSize(Dimension minimumSize)
Sets the minimum size of this component to a constant value. Subsequent calls to getMinimumSize will always return this value. Setting the minimum size to null restores the default behavior.

Parameters:
minimumSize - the new minimum size of this component

setName

public void setName(String name)
Sets the name of the component to the specified string.

Parameters:
name - the string that is to be this component's name

setPreferredSize

public void setPreferredSize(Dimension preferredSize)
Sets the preferred size of this component to a constant value. Subsequent calls to getPreferredSize will always return this value. Setting the preferred size to null restores the default behavior.

Parameters:
preferredSize - The new preferred size, or null

setSize

public void setSize(Dimension d)
Resizes this component so that it has width d.width and height d.height.

Parameters:
d - the dimension specifying the new size of this component

setSize

public void setSize(int width,
                    int height)
Resizes this component so that it has width width and height height.

Parameters:
width - the new width of this component in pixels
height - the new height of this component in pixels

setVisible

public void setVisible(boolean b)
Shows or hides this component depending on the value of parameter b.

Parameters:
b - if true, shows this component; otherwise, hides this component

show

public void show()

show

public void show(boolean b)
Parameters:
b

size

public Dimension size()

toString

public String toString()
Returns a string representation of this component and its values.

Overrides:
toString in class Object
Returns:
a string representation of this component

transferFocus

public void transferFocus()
Transfers the focus to the next component, as though this Component were the focus owner.


transferFocusBackward

public void transferFocusBackward()
Transfers the focus to the previous component, as though this Component were the focus owner.


transferFocusUpCycle

public void transferFocusUpCycle()
Transfers the focus up one focus traversal cycle. Typically, the focus owner is set to this Component's focus cycle root, and the current focus cycle root is set to the new focus owner's focus cycle root. If, however, this Component's focus cycle root is a Window, then the focus owner is set to the focus cycle root's default Component to focus, and the current focus cycle root is unchanged.


update

public void update(Graphics g)
Updates this component.

If this component is not a lightweight component, the AWT calls the update method in response to a call to repaint. You can assume that the background is not cleared.

The update method of Component calls this component's paint method to redraw this component. This method is commonly overridden by subclasses which need to do additional work in response to a call to repaint. Subclasses of Component that override this method should either call super.update(g), or call paint(g) directly from their update method.

The origin of the graphics context, its (00) coordinate point, is the top-left corner of this component. The clipping region of the graphics context is the bounding rectangle of this component.

Note: For more information on the paint mechanisms utilitized by AWT and Swing, including information on how to write the most efficient painting code, see Painting in AWT and Swing.

Parameters:
g - the specified context to use for updating

validate

public void validate()
Ensures that this component has a valid layout. This method is primarily intended to operate on instances of Container.



This documentation differs from the official API. Jadeite adds extra features to the API including: variable font sizes, constructions examples, placeholders for classes and methods, and auto-generated “See Also” links. Additionally it is missing some items found in standard Javadoc documentation, including: generics type information, “Deprecated” tags and comments, “See Also” links, along with other minor differences. Please send any questions or feedback to bam@cs.cmu.edu.
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Copyright 2008 Sun Microsystems, Inc. All rights reserved. Use is subject to license terms. Also see the documentation redistribution policy.
The official Sun™ documentation can be found here at http://java.sun.com/javase/6/docs/api/.