Class Canvas
- java.lang.Object
-
- java.awt.Component
-
- java.awt.Canvas
- All Implemented Interfaces:
-
ImageObserver
,MenuContainer
,Serializable
,Accessible
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.
- Since:
- 1.0
- See Also:
- Serialized Form
Nested Class Summary
Modifier and Type | Class | Description |
---|---|---|
protected class | Canvas.AccessibleAWTCanvas | This class implements accessibility support for the |
Nested classes/interfaces declared in class java.awt.Component
Component.AccessibleAWTComponent, Component.BaselineResizeBehavior, Component.BltBufferStrategy, Component.FlipBufferStrategy
Field Summary
Fields declared in class java.awt.Component
accessibleContext, BOTTOM_ALIGNMENT, CENTER_ALIGNMENT, LEFT_ALIGNMENT, RIGHT_ALIGNMENT, TOP_ALIGNMENT
Fields declared in interface java.awt.image.ImageObserver
ABORT, ALLBITS, ERROR, FRAMEBITS, HEIGHT, PROPERTIES, SOMEBITS, WIDTH
Constructor Summary
Constructor | Description |
---|---|
Canvas() | Constructs a new Canvas. |
Canvas(GraphicsConfiguration config) | Constructs a new Canvas given a GraphicsConfiguration object. |
Method Summary
Modifier and Type | Method | Description |
---|---|---|
void | addNotify() | 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 | getAccessibleContext() | Gets the AccessibleContext associated with this Canvas. |
BufferStrategy | getBufferStrategy() | Returns the |
void | paint(Graphics g) | Paints this canvas. |
void | update(Graphics g) | Updates this canvas. |
Methods declared in class java.awt.Component
action, 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
Methods declared in class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait
Constructor Detail
Canvas
public Canvas()
Constructs a new Canvas.
Canvas
public Canvas(GraphicsConfiguration config)
Constructs 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:
-
GraphicsConfiguration
,Component.getGraphicsConfiguration()
Method Detail
addNotify
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.
- Overrides:
-
addNotify
in classComponent
- See Also:
Component.getToolkit()
paint
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).
- Overrides:
-
paint
in classComponent
- Parameters:
-
g
- the specified Graphics context - See Also:
-
update(Graphics)
,Component.paint(Graphics)
update
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.
- Overrides:
-
update
in classComponent
- Parameters:
-
g
- the specified Graphics context - See Also:
-
paint(Graphics)
,Component.update(Graphics)
createBufferStrategy
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 - Since:
- 1.4
- See Also:
-
Component.isDisplayable()
,getBufferStrategy()
createBufferStrategy
public void createBufferStrategy(int numBuffers, BufferCapabilities caps) throws AWTException
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 benull
- 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 isnull
- Since:
- 1.4
- See Also:
getBufferStrategy()
getBufferStrategy
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
- Since:
- 1.4
- See Also:
createBufferStrategy(int)
getAccessibleContext
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.
- Specified by:
-
getAccessibleContext
in interfaceAccessible
- Overrides:
-
getAccessibleContext
in classComponent
- Returns:
- an AccessibleAWTCanvas that serves as the AccessibleContext of this Canvas
- Since:
- 1.3