Class Canvas
- All Implemented Interfaces:
- ImageObserver,- MenuContainer,- Serializable,- Accessible
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.
- Since:
- 1.0
- See Also:
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Nested Class SummaryNested ClassesModifier and TypeClassDescriptionprotected classThis class implements accessibility support for theCanvasclass.Nested classes/interfaces declared in class java.awt.ComponentComponent.AccessibleAWTComponent, Component.BaselineResizeBehavior, Component.BltBufferStrategy, Component.FlipBufferStrategy
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Field SummaryFields declared in class java.awt.ComponentaccessibleContext, BOTTOM_ALIGNMENT, CENTER_ALIGNMENT, LEFT_ALIGNMENT, RIGHT_ALIGNMENT, TOP_ALIGNMENTFields declared in interface java.awt.image.ImageObserverABORT, ALLBITS, ERROR, FRAMEBITS, HEIGHT, PROPERTIES, SOMEBITS, WIDTH
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Constructor SummaryConstructorsConstructorDescriptionCanvas()Constructs a new Canvas.Canvas(GraphicsConfiguration config) Constructs a new Canvas given a GraphicsConfiguration object.
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Method SummaryModifier and TypeMethodDescriptionvoidCreates the peer of the canvas.voidcreateBufferStrategy(int numBuffers) Creates a new strategy for multi-buffering on this component.voidcreateBufferStrategy(int numBuffers, BufferCapabilities caps) Creates a new strategy for multi-buffering on this component with the required buffer capabilities.Gets the AccessibleContext associated with this Canvas.Returns theBufferStrategyused by this component.voidPaints this canvas.voidUpdates this canvas.Methods declared in class java.awt.Componentaction, add, addComponentListener, addFocusListener, addHierarchyBoundsListener, addHierarchyListener, addInputMethodListener, addKeyListener, addMouseListener, addMouseMotionListener, addMouseWheelListener, addPropertyChangeListener, addPropertyChangeListener, applyComponentOrientation, areFocusTraversalKeysSet, bounds, checkImage, checkImage, coalesceEvents, contains, contains, createImage, createImage, createVolatileImage, createVolatileImage, deliverEvent, disable, disableEvents, dispatchEvent, doLayout, enable, enable, enableEvents, enableInputMethods, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, getAlignmentX, getAlignmentY, getBackground, getBaseline, getBaselineResizeBehavior, getBounds, getBounds, getColorModel, getComponentAt, getComponentAt, getComponentListeners, getComponentOrientation, getCursor, getDropTarget, getFocusCycleRootAncestor, getFocusListeners, getFocusTraversalKeys, getFocusTraversalKeysEnabled, getFont, getFontMetrics, getForeground, getGraphics, getGraphicsConfiguration, getHeight, getHierarchyBoundsListeners, getHierarchyListeners, getIgnoreRepaint, getInputContext, getInputMethodListeners, getInputMethodRequests, getKeyListeners, getListeners, getLocale, getLocation, getLocation, getLocationOnScreen, getMaximumSize, getMinimumSize, getMouseListeners, getMouseMotionListeners, getMousePosition, getMouseWheelListeners, getName, getParent, getPreferredSize, getPropertyChangeListeners, getPropertyChangeListeners, getSize, getSize, getToolkit, getTreeLock, getWidth, getX, getY, gotFocus, handleEvent, hasFocus, hide, imageUpdate, inside, invalidate, isBackgroundSet, isCursorSet, isDisplayable, isDoubleBuffered, isEnabled, isFocusable, isFocusCycleRoot, isFocusOwner, isFocusTraversable, isFontSet, isForegroundSet, isLightweight, isMaximumSizeSet, isMinimumSizeSet, isOpaque, isPreferredSizeSet, isShowing, isValid, isVisible, keyDown, keyUp, layout, list, list, list, list, list, locate, location, lostFocus, minimumSize, mouseDown, mouseDrag, mouseEnter, mouseExit, mouseMove, mouseUp, move, nextFocus, paintAll, paramString, postEvent, preferredSize, prepareImage, prepareImage, print, printAll, processComponentEvent, processEvent, processFocusEvent, processHierarchyBoundsEvent, processHierarchyEvent, processInputMethodEvent, processKeyEvent, processMouseEvent, processMouseMotionEvent, processMouseWheelEvent, remove, removeComponentListener, removeFocusListener, removeHierarchyBoundsListener, removeHierarchyListener, removeInputMethodListener, removeKeyListener, removeMouseListener, removeMouseMotionListener, removeMouseWheelListener, removeNotify, removePropertyChangeListener, removePropertyChangeListener, repaint, repaint, repaint, repaint, requestFocus, requestFocus, requestFocus, requestFocus, requestFocusInWindow, requestFocusInWindow, requestFocusInWindow, reshape, resize, resize, revalidate, setBackground, setBounds, setBounds, setComponentOrientation, setCursor, setDropTarget, setEnabled, setFocusable, setFocusTraversalKeys, setFocusTraversalKeysEnabled, setFont, setForeground, setIgnoreRepaint, setLocale, setLocation, setLocation, setMaximumSize, setMinimumSize, setMixingCutoutShape, setName, setPreferredSize, setSize, setSize, setVisible, show, show, size, toString, transferFocus, transferFocusBackward, transferFocusUpCycle, validate
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Constructor Details- 
Canvaspublic Canvas()Constructs a new Canvas.
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CanvasConstructs a new Canvas given a GraphicsConfiguration object. If null is passed, then the default GraphicsConfiguration will be used.- Parameters:
- config- a reference to a GraphicsConfiguration object or null
- See Also:
 
 
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Method Details- 
addNotify
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paintPaints this canvas.Most applications that subclass Canvasshould 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).
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updateUpdates 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'spaintmethod. Note: applications that override this method should either call super.update(g) or incorporate the functionality described above into their own code.
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createBufferStrategypublic 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 aBufferStrategywith 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
- Since:
- 1.4
- See Also:
 
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createBufferStrategyCreates 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
- Since:
- 1.4
- See Also:
 
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getBufferStrategyReturns theBufferStrategyused by this component. This method will return null if aBufferStrategyhas not yet been created or has been disposed.- Returns:
- the buffer strategy used by this component
- Since:
- 1.4
- See Also:
 
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getAccessibleContextGets the AccessibleContext associated with this Canvas. For canvases, the AccessibleContext takes the form of an AccessibleAWTCanvas. A new AccessibleAWTCanvas instance is created if necessary.- Specified by:
- getAccessibleContextin interface- Accessible
- Overrides:
- getAccessibleContextin class- Component
- Returns:
- an AccessibleAWTCanvas that serves as the AccessibleContext of this Canvas
- Since:
- 1.3
 
 
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