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public class Canvas extends Component implements Accessible
A Canvas
component represents a blank rectangular
area of the screen onto which the application can draw or from
which the application can trap input events from the user.
An application must subclass the Canvas
class in
order to get useful functionality such as creating a custom
component. The paint
method must be overridden
in order to perform custom graphics on the canvas.
Nested Class Summary | |
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protected class |
This class implements accessibility support for the Canvas class. |
Nested classes/interfaces inherited from class java.awt.Component |
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Component.AccessibleAWTComponent, Component.BaselineResizeBehavior, Component.BltBufferStrategy, Component.FlipBufferStrategy |
Field Summary |
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Fields inherited from class java.awt.Component |
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BOTTOM_ALIGNMENT, CENTER_ALIGNMENT, LEFT_ALIGNMENT, RIGHT_ALIGNMENT, TOP_ALIGNMENT |
Constructor Summary | |
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Canvas() Constructs a new Canvas. |
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Canvas(GraphicsConfiguration config) Constructs a new Canvas given a GraphicsConfiguration object. |
Method Summary | |
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void |
Creates the peer of the canvas. |
void |
createBufferStrategy(int numBuffers) Creates a new strategy for multi-buffering on this component. |
void |
createBufferStrategy(int numBuffers, BufferCapabilities caps) Creates a new strategy for multi-buffering on this component with the required buffer capabilities. |
AccessibleContext |
Gets the AccessibleContext associated with this Canvas. |
BufferStrategy |
Returns the BufferStrategy used by this component.
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void |
Paints this canvas. |
void |
Updates this canvas. |
Methods inherited from class java.lang.Object |
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clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait |
Constructor Detail |
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public Canvas()
public Canvas(GraphicsConfiguration config)
config
- a reference to a GraphicsConfiguration object.Method Detail |
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public void addNotify()
addNotify
in class Component
public void createBufferStrategy(int numBuffers)
BufferStrategy
with that number of buffers.
A page-flipping strategy is attempted first, then a blitting strategy
using accelerated buffers. Finally, an unaccelerated blitting
strategy is used.
Each time this method is called, the existing buffer strategy for this component is discarded.
createBufferStrategy
in class Component
numBuffers
- number of buffers to create, including the front bufferpublic void createBufferStrategy(int numBuffers, BufferCapabilities caps) throws AWTException
Each time this method is called, the existing buffer strategy for this component is discarded.
createBufferStrategy
in class Component
numBuffers
- number of buffers to createcaps
- the required capabilities for creating the buffer strategy;
cannot be null
AWTException
- if the capabilities supplied could not be
supported or met; this may happen, for example, if there is not enough
accelerated memory currently available, or if page flipping is specified
but not possible.public AccessibleContext getAccessibleContext()
getAccessibleContext
in class Component
public BufferStrategy getBufferStrategy()
BufferStrategy
used by this component. This
method will return null if a BufferStrategy
has not yet
been created or has been disposed.
getBufferStrategy
in class Component
public void paint(Graphics g)
Most applications that subclass Canvas
should
override this method in order to perform some useful operation
(typically, custom painting of the canvas).
The default operation is simply to clear the canvas.
Applications that override this method need not call
super.paint(g).
paint
in class Component
g
- the specified Graphics contextpublic void update(Graphics g)
This method is called in response to a call to repaint
.
The canvas is first cleared by filling it with the background
color, and then completely redrawn by calling this canvas's
paint
method.
Note: applications that override this method should either call
super.update(g) or incorporate the functionality described
above into their own code.
update
in class Component
g
- the specified Graphics context
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