public class

Canvas

extends Component
implements Accessible
java.lang.Object
   ↳ java.awt.Component
     ↳ java.awt.Canvas

Class Overview

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.

Summary

Nested Classes
class Canvas.AccessibleAWTCanvas This class implements accessibility support for the Canvas class. 
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Inherited Constants
From class java.awt.Component
From interface java.awt.image.ImageObserver
Public Constructors
Canvas()
Constructs a new Canvas.
Canvas(GraphicsConfiguration config)
Constructs a new Canvas given a GraphicsConfiguration object.
Public Methods
void addNotify()
Creates the peer of the canvas.
void createBufferStrategy(int numBuffers, BufferCapabilities caps)
Creates a new strategy for multi-buffering on this component with the required buffer capabilities.
void createBufferStrategy(int numBuffers)
Creates a new strategy for multi-buffering on this component.
AccessibleContext getAccessibleContext()
Gets the AccessibleContext associated with this Canvas.
BufferStrategy getBufferStrategy()
Returns the BufferStrategy used by this component.
void paint(Graphics g)
Paints this canvas.
void update(Graphics g)
Updates this canvas.
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Inherited Methods
From class java.awt.Component
From class java.lang.Object
From interface java.awt.MenuContainer
From interface java.awt.image.ImageObserver
From interface javax.accessibility.Accessible

Public Constructors

public Canvas ()

Constructs a new Canvas.

public Canvas (GraphicsConfiguration config)

Constructs a new Canvas given a GraphicsConfiguration object.

Parameters
config a reference to a GraphicsConfiguration object.
See Also

Public Methods

public void addNotify ()

Creates the peer of the canvas. This peer allows you to change the user interface of the canvas without changing its functionality.

See Also

public void createBufferStrategy (int numBuffers, BufferCapabilities caps)

Creates a new strategy for multi-buffering on this component with the required buffer capabilities. This is useful, for example, if only accelerated memory or page flipping is desired (as specified by the buffer capabilities).

Each time this method is called, the existing buffer strategy for this component is discarded.

Parameters
numBuffers number of buffers to create
caps the required capabilities for creating the buffer strategy; cannot be null
Throws
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.
IllegalArgumentException if numBuffers is less than 1, or if caps is null
See Also

public void createBufferStrategy (int numBuffers)

Creates a new strategy for multi-buffering on this component. Multi-buffering is useful for rendering performance. This method attempts to create the best strategy available with the number of buffers supplied. It will always create a 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.

Parameters
numBuffers number of buffers to create, including the front buffer
Throws
IllegalArgumentException if numBuffers is less than 1.
IllegalStateException if the component is not displayable
See Also

public AccessibleContext getAccessibleContext ()

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

Returns
  • an AccessibleAWTCanvas that serves as the AccessibleContext of this Canvas

public BufferStrategy getBufferStrategy ()

Returns the BufferStrategy used by this component. This method will return null if a BufferStrategy has not yet been created or has been disposed.

Returns
  • the buffer strategy used by this component
See Also

public void paint (Graphics g)

Paints this canvas.

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).

Parameters
g the specified Graphics context
See Also

public void update (Graphics g)

Updates this canvas.

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.

Parameters
g the specified Graphics context
See Also