File	Doc	Category	Size	Date	Package
Canvas.java	API Doc	Java SE 5 API	7348	Fri Aug 26 14:56:44 BST 2005	java.awt

Canvas

• java.lang.Object
  • java.awt.Component

Fields Summary
private static final String	base
private static int	nameCounter
private static final long	serialVersionUID

Constructors Summary
public Canvas() Constructs a new Canvas.
public Canvas(GraphicsConfiguration config) Constructs a new Canvas given a GraphicsConfiguration object. param config a reference to a GraphicsConfiguration object. see GraphicsConfiguration this(); graphicsConfig = config;

Methods Summary
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 java.awt.Toolkit#createCanvas(java.awt.Canvas) see java.awt.Component#getToolkit() synchronized (getTreeLock()) { if (peer == null) peer = getToolkit().createCanvas(this); super.addNotify(); }
java.lang.String	constructComponentName() Construct a name for this component. Called by getName() when the name is null. synchronized (getClass()) { return base + nameCounter++; }
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. param numBuffers number of buffers to create, including the front buffer exception IllegalArgumentException if numBuffers is less than 1. exception IllegalStateException if the component is not displayable see #isDisplayable see #getBufferStrategy since 1.4 super.createBufferStrategy(numBuffers);
public void	createBufferStrategy(int numBuffers, java.awt.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. param numBuffers number of buffers to create param caps the required capabilities for creating the buffer strategy; cannot be null exception 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. exception IllegalArgumentException if numBuffers is less than 1, or if caps is null see #getBufferStrategy since 1.4 super.createBufferStrategy(numBuffers, caps);
public javax.accessibility.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. return an AccessibleAWTCanvas that serves as the AccessibleContext of this Canvas if (accessibleContext == null) { accessibleContext = new AccessibleAWTCanvas(); } return accessibleContext;
public java.awt.image.BufferStrategy	getBufferStrategy() return the buffer strategy used by this component see #createBufferStrategy since 1.4 return super.getBufferStrategy();
public void	paint(java.awt.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). param g the specified Graphics context see #update(Graphics) see Component#paint(Graphics) g.clearRect(0, 0, width, height);
boolean	postsOldMouseEvents() return true;
public void	update(java.awt.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. param g the specified Graphics context see #paint(Graphics) see Component#update(Graphics) g.clearRect(0, 0, width, height); paint(g);