javax.swing
class JScrollBar

java.lang.Object java.awt.Component java.awt.Container javax.swing.JComponent javax.swing.JScrollBar

All Implemented Interfaces:

Adjustable, MenuContainer, ImageObserver, Serializable, Accessible, TransferHandler.HasGetTransferHandler

Direct Known Subclasses:

JScrollPane.ScrollBar

Most common ways to construct:

JScrollPane scrollPane = …;

JScrollBar hBar = scrollPane.getHorizontalScrollBar();

Based on 30 examples

 

JScrollPane scrollPane = …;

JScrollBar vBar = scrollPane.getVerticalScrollBar();

Based on 30 examples

public class JScrollBar
extends JComponent
implements Adjustable, Accessible

An implementation of a scrollbar. The user positions the knob in the scrollbar to determine the contents of the viewing area. The program typically adjusts the display so that the end of the scrollbar represents the end of the displayable contents, or 100% of the contents. The start of the scrollbar is the beginning of the displayable contents, or 0%. The position of the knob within those bounds then translates to the corresponding percentage of the displayable contents.

Typically, as the position of the knob in the scrollbar changes a corresponding change is made to the position of the JViewport on the underlying view, changing the contents of the JViewport.

Warning: Swing is not thread safe. For more information see Swing's Threading Policy.

Warning: Serialized objects of this class will not be compatible with future Swing releases. The current serialization support is appropriate for short term storage or RMI between applications running the same version of Swing. As of 1.4, support for long term storage of all JavaBeans^TM has been added to the java.beans package. Please see {@link java.beans.XMLEncoder}.

blockIncrement

protected int blockIncrement

model

protected BoundedRangeModel model

The model that represents the scrollbar's minimum, maximum, extent (aka "visibleAmount") and current value.

orientation

protected int orientation

unitIncrement

protected int unitIncrement

JScrollBar

public JScrollBar()

Creates a vertical scrollbar with the following initial values:

 minimum = 0 
 maximum = 100 
 value = 0
 extent = 10
 

JScrollBar

public JScrollBar(int orientation)

Creates a scrollbar with the specified orientation and the following initial values:

 minimum = 0 
 maximum = 100 
 value = 0
 extent = 10
 

Parameters:

orientation

JScrollBar

public JScrollBar(int orientation,
                  int value,
                  int extent,
                  int min,
                  int max)

Creates a scrollbar with the specified orientation, value, extent, minimum, and maximum. The "extent" is the size of the viewable area. It is also known as the "visible amount".

Note: Use setBlockIncrement to set the block increment to a size slightly smaller than the view's extent. That way, when the user jumps the knob to an adjacent position, one or two lines of the original contents remain in view.

Parameters:

orientation

value

extent

min

max

addAdjustmentListener

public void addAdjustmentListener(AdjustmentListener l)

Adds an AdjustmentListener. Adjustment listeners are notified each time the scrollbar's model changes. Adjustment events are provided for backwards compatibility with java.awt.Scrollbar.

Note that the AdjustmentEvents type property will always have a placeholder value of AdjustmentEvent.TRACK because all changes to a BoundedRangeModels value are considered equivalent. To change the value of a BoundedRangeModel one just sets its value property, i.e. model.setValue(123). No information about the origin of the change, e.g. it's a block decrement, is provided. We don't try fabricate the origin of the change here.

Parameters:

l - the AdjustmentLister to add

fireAdjustmentValueChanged

protected void fireAdjustmentValueChanged(int id,
                                          int type,
                                          int value)

Notify listeners that the scrollbar's model has changed.

Parameters:

id

type

value

getAccessibleContext

public AccessibleContext getAccessibleContext()

Gets the AccessibleContext associated with this JScrollBar. For JScrollBar, the AccessibleContext takes the form of an AccessibleJScrollBar. A new AccessibleJScrollBar instance is created if necessary.

Overrides:

getAccessibleContext in class JComponent

Returns:

an AccessibleJScrollBar that serves as the AccessibleContext of this JScrollBar

getAdjustmentListeners

public AdjustmentListener[] getAdjustmentListeners()

Returns an array of all the AdjustmentListeners added to this JScrollBar with addAdjustmentListener().

Returns:

all of the AdjustmentListeners added or an empty array if no listeners have been added

getBlockIncrement

public int getBlockIncrement()

For backwards compatibility with java.awt.Scrollbar.

getBlockIncrement

public int getBlockIncrement(int direction)

Returns the amount to change the scrollbar's value by, given a block (usually "page") up/down request. A ScrollBarUI implementation typically calls this method when the user clicks above or below the scrollbar "knob" to change the value up or down by large amount. Subclasses my override this method to compute a value, e.g. the change required to scroll up or down one paragraph in a text document.

The JScrollPane component creates scrollbars (by default) that override this method and delegate to the viewports Scrollable view, if it has one. The Scrollable interface provides a more specialized version of this method.

Parameters:

direction - is -1 or 1 for up/down respectively

Returns:

the value of the blockIncrement property

getMaximum

public int getMaximum()

The maximum value of the scrollbar is maximum - extent.

Returns:

the value of the model's maximum property

getMaximumSize

public Dimension getMaximumSize()

The scrollbar is flexible along it's scrolling axis and rigid along the other axis.

Overrides:

getMaximumSize in class JComponent

getMinimum

public int getMinimum()

Returns the minimum value supported by the scrollbar (usually zero).

Returns:

the value of the model's minimum property

getMinimumSize

public Dimension getMinimumSize()

The scrollbar is flexible along it's scrolling axis and rigid along the other axis.

Overrides:

getMinimumSize in class JComponent

getModel

public BoundedRangeModel getModel()

Returns data model that handles the scrollbar's four fundamental properties: minimum, maximum, value, extent.

getOrientation

public int getOrientation()

Returns the component's orientation (horizontal or vertical).

Returns:

VERTICAL or HORIZONTAL

getUI

public ScrollBarUI getUI()

Returns the delegate that implements the look and feel for this component.

getUIClassID

public String getUIClassID()

Returns the name of the LookAndFeel class for this component.

Overrides:

getUIClassID in class JComponent

Returns:

"ScrollBarUI"

getUnitIncrement

public int getUnitIncrement()

For backwards compatibility with java.awt.Scrollbar.

getUnitIncrement

public int getUnitIncrement(int direction)

Returns the amount to change the scrollbar's value by, given a unit up/down request. A ScrollBarUI implementation typically calls this method when the user clicks on a scrollbar up/down arrow and uses the result to update the scrollbar's value. Subclasses my override this method to compute a value, e.g. the change required to scroll up or down one (variable height) line text or one row in a table.

The JScrollPane component creates scrollbars (by default) that override this method and delegate to the viewports Scrollable view, if it has one. The Scrollable interface provides a more specialized version of this method.

Parameters:

direction - is -1 or 1 for up/down respectively

Returns:

the value of the unitIncrement property

getValue

public int getValue()

Returns the scrollbar's value.

Returns:

the model's value property

getValueIsAdjusting

public boolean getValueIsAdjusting()

True if the scrollbar knob is being dragged.

Returns:

the value of the model's valueIsAdjusting property

getVisibleAmount

public int getVisibleAmount()

Returns the scrollbar's extent, aka its "visibleAmount". In many scrollbar look and feel implementations the size of the scrollbar "knob" or "thumb" is proportional to the extent.

Returns:

the value of the model's extent property

paramString

protected String paramString()

Returns a string representation of this JScrollBar. 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.

Overrides:

paramString in class JComponent

Returns:

a string representation of this JScrollBar.

removeAdjustmentListener

public void removeAdjustmentListener(AdjustmentListener l)

Removes an AdjustmentEvent listener.

Parameters:

l - the AdjustmentLister to remove

setBlockIncrement

public void setBlockIncrement(int blockIncrement)

Sets the blockIncrement property.

Note, that if the argument is equal to the value of Integer.MIN_VALUE, the most look and feels will not provide the scrolling to the right/down.

Parameters:

blockIncrement

setEnabled

public void setEnabled(boolean x)

Enables the component so that the knob position can be changed. When the disabled, the knob position cannot be changed.

Overrides:

setEnabled in class JComponent

Parameters:

x - a boolean value, where true enables the component and false disables it

setMaximum

public void setMaximum(int maximum)

Sets the model's maximum property. Note that the scrollbar's value can only be set to maximum - extent.

Parameters:

maximum

setMinimum

public void setMinimum(int minimum)

Sets the model's minimum property.

Parameters:

minimum

setModel

public void setModel(BoundedRangeModel newModel)

Sets the model that handles the scrollbar's four fundamental properties: minimum, maximum, value, extent.

Parameters:

newModel

setOrientation

public void setOrientation(int orientation)

Set the scrollbar's orientation to either VERTICAL or HORIZONTAL.

Parameters:

orientation

setUI

public void setUI(ScrollBarUI ui)

Sets the L&F object that renders this component.

Parameters:

ui - the ScrollBarUI L&F object

setUnitIncrement

public void setUnitIncrement(int unitIncrement)

Sets the unitIncrement property.

Note, that if the argument is equal to the value of Integer.MIN_VALUE, the most look and feels will not provide the scrolling to the right/down.

Parameters:

unitIncrement

setValue

public void setValue(int value)

Sets the scrollbar's value. This method just forwards the value to the model.

Parameters:

value

setValueIsAdjusting

public void setValueIsAdjusting(boolean b)

Sets the model's valueIsAdjusting property. Scrollbar look and feel implementations should set this property to true when a knob drag begins, and to false when the drag ends. The scrollbar model will not generate ChangeEvents while valueIsAdjusting is true.

Parameters:

b

setValues

public void setValues(int newValue,
                      int newExtent,
                      int newMin,
                      int newMax)

Sets the four BoundedRangeModel properties after forcing the arguments to obey the usual constraints:

 minimum <= value <= value+extent <= maximum
 

Parameters:

newValue

newExtent

newMin

newMax

setVisibleAmount

public void setVisibleAmount(int extent)

Set the model's extent property.

Parameters:

extent

updateUI

public void updateUI()

Overrides JComponent.updateUI.

Overrides:

updateUI in class JComponent