java.awt
Class Component

java.lang.Object
  java.awt.Component

All Implemented Interfaces:

ImageObserver, MenuContainer, Serializable

Direct Known Subclasses:

Button, Canvas, Checkbox, Choice, Container, Label, List, Scrollbar, TextComponent

public abstract class Component
extends Object
implements ImageObserver, MenuContainer, Serializable

A component is an object having a graphical representation that can be displayed on the screen and that can interact with the user. Examples of components are the buttons, checkboxes, and scrollbars of a typical graphical user interface.

The Component class is the abstract superclass of the nonmenu-related Abstract Window Toolkit components. Class Component can also be extended directly to create a lightweight component. A lightweight component is a component that is not associated with a native opaque window.

Serialization

    import java.awt.*;
    import java.awt.event.*;
    import java.io.Serializable;
    
    class MyApp implements ActionListener, Serializable
    {
        BigObjectThatShouldNotBeSerializedWithAButton bigOne;
        Button aButton = new Button();
      
        MyApp()
        {
            // Oops, now aButton has a listener with a reference
            // to bigOne!
            aButton.addActionListener(this);
        }
    
        public void actionPerformed(ActionEvent e)
        {
            System.out.println("Hello There");
        }
    }
 

    import java.awt.*;
    import java.awt.event.*;
    import java.io.Serializable;

    class MyApp java.io.Serializable
    {
         BigObjectThatShouldNotBeSerializedWithAButton bigOne;
         Button aButton = new Button();

         static class MyActionListener implements ActionListener
         {
             public void actionPerformed(ActionEvent e)
             {
                 System.out.println("Hello There");
             }
         }
 
         MyApp()
         {
             aButton.addActionListener(new MyActionListener());
         }
    }
 

Note: For more information on the paint mechanisms utilitized by AWT and Swing, including information on how to write the most efficient painting code, see Painting in AWT and Swing.

For details on the focus subsystem, see How to Use the Focus Subsystem, a section in The Java Tutorial, and the Focus Specification for more information.

See Also:

Serialized Form

Nested Class Summary
protected  class	Component.AccessibleAWTComponent           Inner class of Component used to provide default support for accessibility.
static class	Component.BaselineResizeBehavior           Enumeration of the common ways the baseline of a component can change as the size changes.
protected  class	Component.BltBufferStrategy           Inner class for blitting offscreen surfaces to a component.
protected  class	Component.FlipBufferStrategy           Inner class for flipping buffers on a component.

 

Field Summary
static float	BOTTOM_ALIGNMENT           Ease-of-use constant for getAlignmentY.
static float	CENTER_ALIGNMENT           Ease-of-use constant for getAlignmentY and getAlignmentX.
static float	LEFT_ALIGNMENT           Ease-of-use constant for getAlignmentX.
static float	RIGHT_ALIGNMENT           Ease-of-use constant for getAlignmentX.
static float	TOP_ALIGNMENT           Ease-of-use constant for getAlignmentY().

 

Fields inherited from interface java.awt.image.ImageObserver
ABORT, ALLBITS, ERROR, FRAMEBITS, HEIGHT, PROPERTIES, SOMEBITS, WIDTH

 

Constructor Summary
protected	Component()           Constructs a new component.

 

Method Summary
boolean	action(Event evt, Object what)           Deprecated. As of JDK version 1.1, should register this component as ActionListener on component which fires action events.
void	add(PopupMenu popup)           Adds the specified popup menu to the component.
void	addComponentListener(ComponentListener l)           Adds the specified component listener to receive component events from this component.
void	addFocusListener(FocusListener l)           Adds the specified focus listener to receive focus events from this component when this component gains input focus.
void	addHierarchyBoundsListener(HierarchyBoundsListener l)           Adds the specified hierarchy bounds listener to receive hierarchy bounds events from this component when the hierarchy to which this container belongs changes.
void	addHierarchyListener(HierarchyListener l)           Adds the specified hierarchy listener to receive hierarchy changed events from this component when the hierarchy to which this container belongs changes.
void	addInputMethodListener(InputMethodListener l)           Adds the specified input method listener to receive input method events from this component.
void	addKeyListener(KeyListener l)           Adds the specified key listener to receive key events from this component.
void	addMouseListener(MouseListener l)           Adds the specified mouse listener to receive mouse events from this component.
void	addMouseMotionListener(MouseMotionListener l)           Adds the specified mouse motion listener to receive mouse motion events from this component.
void	addMouseWheelListener(MouseWheelListener l)           Adds the specified mouse wheel listener to receive mouse wheel events from this component.
void	addNotify()           Makes this Component displayable by connecting it to a native screen resource.
void	addPropertyChangeListener(PropertyChangeListener listener)           Adds a PropertyChangeListener to the listener list.
void	addPropertyChangeListener(String propertyName, PropertyChangeListener listener)           Adds a PropertyChangeListener to the listener list for a specific property.
void	applyComponentOrientation(ComponentOrientation orientation)           Sets the ComponentOrientation property of this component and all components contained within it.
boolean	areFocusTraversalKeysSet(int id)           Returns whether the Set of focus traversal keys for the given focus traversal operation has been explicitly defined for this Component.
Rectangle	bounds()           Deprecated. As of JDK version 1.1, replaced by getBounds().
int	checkImage(Image image, ImageObserver observer)           Returns the status of the construction of a screen representation of the specified image.
int	checkImage(Image image, int width, int height, ImageObserver observer)           Returns the status of the construction of a screen representation of the specified image.
protected  AWTEvent	coalesceEvents(AWTEvent existingEvent, AWTEvent newEvent)           Potentially coalesce an event being posted with an existing event.
boolean	contains(int x, int y)           Checks whether this component "contains" the specified point, where x and y are defined to be relative to the coordinate system of this component.
boolean	contains(Point p)           Checks whether this component "contains" the specified point, where the point's x and y coordinates are defined to be relative to the coordinate system of this component.
Image	createImage(ImageProducer producer)           Creates an image from the specified image producer.
Image	createImage(int width, int height)           Creates an off-screen drawable image to be used for double buffering.
VolatileImage	createVolatileImage(int width, int height)           Creates a volatile off-screen drawable image to be used for double buffering.
VolatileImage	createVolatileImage(int width, int height, ImageCapabilities caps)           Creates a volatile off-screen drawable image, with the given capabilities.
void	deliverEvent(Event e)           Deprecated. As of JDK version 1.1, replaced by dispatchEvent(AWTEvent e).
void	disable()           Deprecated. As of JDK version 1.1, replaced by setEnabled(boolean).
protected  void	disableEvents(long eventsToDisable)           Disables the events defined by the specified event mask parameter from being delivered to this component.
void	dispatchEvent(AWTEvent e)           Dispatches an event to this component or one of its sub components.
void	doLayout()           Prompts the layout manager to lay out this component.
void	enable()           Deprecated. As of JDK version 1.1, replaced by setEnabled(boolean).
void	enable(boolean b)           Deprecated. As of JDK version 1.1, replaced by setEnabled(boolean).
protected  void	enableEvents(long eventsToEnable)           Enables the events defined by the specified event mask parameter to be delivered to this component.
void	enableInputMethods(boolean enable)           Enables or disables input method support for this component.
protected  void	firePropertyChange(String propertyName, boolean oldValue, boolean newValue)           Support for reporting bound property changes for boolean properties.
void	firePropertyChange(String propertyName, byte oldValue, byte newValue)           Reports a bound property change.
void	firePropertyChange(String propertyName, char oldValue, char newValue)           Reports a bound property change.
void	firePropertyChange(String propertyName, double oldValue, double newValue)           Reports a bound property change.
void	firePropertyChange(String propertyName, float oldValue, float newValue)           Reports a bound property change.
protected  void	firePropertyChange(String propertyName, int oldValue, int newValue)           Support for reporting bound property changes for integer properties.
void	firePropertyChange(String propertyName, long oldValue, long newValue)           Reports a bound property change.
protected  void	firePropertyChange(String propertyName, Object oldValue, Object newValue)           Support for reporting bound property changes for Object properties.
void	firePropertyChange(String propertyName, short oldValue, short newValue)           Reports a bound property change.
AccessibleContext	getAccessibleContext()           Gets the AccessibleContext associated with this Component.
float	getAlignmentX()           Returns the alignment along the x axis.
float	getAlignmentY()           Returns the alignment along the y axis.
Color	getBackground()           Gets the background color of this component.
int	getBaseline(int width, int height)           Returns the baseline.
Component.BaselineResizeBehavior	getBaselineResizeBehavior()           Returns an enum indicating how the baseline of the component changes as the size changes.
Rectangle	getBounds()           Gets the bounds of this component in the form of a Rectangle object.
Rectangle	getBounds(Rectangle rv)           Stores the bounds of this component into "return value" rv and return rv.
ColorModel	getColorModel()           Gets the instance of ColorModel used to display the component on the output device.
Component	getComponentAt(int x, int y)           Determines if this component or one of its immediate subcomponents contains the (x, y) location, and if so, returns the containing component.
Component	getComponentAt(Point p)           Returns the component or subcomponent that contains the specified point.
ComponentListener[]	getComponentListeners()           Returns an array of all the component listeners registered on this component.
ComponentOrientation	getComponentOrientation()           Retrieves the language-sensitive orientation that is to be used to order the elements or text within this component.
Cursor	getCursor()           Gets the cursor set in the component.
DropTarget	getDropTarget()           Gets the DropTarget associated with this Component.
Container	getFocusCycleRootAncestor()           Returns the Container which is the focus cycle root of this Component's focus traversal cycle.
FocusListener[]	getFocusListeners()           Returns an array of all the focus listeners registered on this component.
Set<AWTKeyStroke>	getFocusTraversalKeys(int id)           Returns the Set of focus traversal keys for a given traversal operation for this Component.
boolean	getFocusTraversalKeysEnabled()           Returns whether focus traversal keys are enabled for this Component.
Font	getFont()           Gets the font of this component.
FontMetrics	getFontMetrics(Font font)           Gets the font metrics for the specified font.
Color	getForeground()           Gets the foreground color of this component.
Graphics	getGraphics()           Creates a graphics context for this component.
GraphicsConfiguration	getGraphicsConfiguration()           Gets the GraphicsConfiguration associated with this Component.
int	getHeight()           Returns the current height of this component.
HierarchyBoundsListener[]	getHierarchyBoundsListeners()           Returns an array of all the hierarchy bounds listeners registered on this component.
HierarchyListener[]	getHierarchyListeners()           Returns an array of all the hierarchy listeners registered on this component.
boolean	getIgnoreRepaint()
InputContext	getInputContext()           Gets the input context used by this component for handling the communication with input methods when text is entered in this component.
InputMethodListener[]	getInputMethodListeners()           Returns an array of all the input method listeners registered on this component.
InputMethodRequests	getInputMethodRequests()           Gets the input method request handler which supports requests from input methods for this component.
KeyListener[]	getKeyListeners()           Returns an array of all the key listeners registered on this component.
<T extends EventListener> T[]	getListeners(Class<T> listenerType)           Returns an array of all the objects currently registered as FooListeners upon this Component.
Locale	getLocale()           Gets the locale of this component.
Point	getLocation()           Gets the location of this component in the form of a point specifying the component's top-left corner.
Point	getLocation(Point rv)           Stores the x,y origin of this component into "return value" rv and return rv.
Point	getLocationOnScreen()           Gets the location of this component in the form of a point specifying the component's top-left corner in the screen's coordinate space.
Dimension	getMaximumSize()           Gets the maximum size of this component.
Dimension	getMinimumSize()           Gets the mininimum size of this component.
MouseListener[]	getMouseListeners()           Returns an array of all the mouse listeners registered on this component.
MouseMotionListener[]	getMouseMotionListeners()           Returns an array of all the mouse motion listeners registered on this component.
Point	getMousePosition()           Returns the position of the mouse pointer in this Component's coordinate space if the Component is directly under the mouse pointer, otherwise returns null.
MouseWheelListener[]	getMouseWheelListeners()           Returns an array of all the mouse wheel listeners registered on this component.
String	getName()           Gets the name of the component.
Container	getParent()           Gets the parent of this component.
java.awt.peer.ComponentPeer	getPeer()           Deprecated. As of JDK version 1.1, programs should not directly manipulate peers; replaced by boolean isDisplayable().
Dimension	getPreferredSize()           Gets the preferred size of this component.
PropertyChangeListener[]	getPropertyChangeListeners()           Returns an array of all the property change listeners registered on this component.
PropertyChangeListener[]	getPropertyChangeListeners(String propertyName)           Returns an array of all the listeners which have been associated with the named property.
Dimension	getSize()           Returns the size of this component in the form of a Dimension object.
Dimension	getSize(Dimension rv)           Stores the width/height of this component into "return value" rv and return rv.
Toolkit	getToolkit()           Gets the toolkit of this component.
Object	getTreeLock()           Gets this component's locking object (the object that owns the thread sychronization monitor) for AWT component-tree and layout operations.
int	getWidth()           Returns the current width of this component.
int	getX()           Returns the current x coordinate of the components origin.
int	getY()           Returns the current y coordinate of the components origin.
boolean	gotFocus(Event evt, Object what)           Deprecated. As of JDK version 1.1, replaced by processFocusEvent(FocusEvent).
boolean	handleEvent(Event evt)           Deprecated. As of JDK version 1.1 replaced by processEvent(AWTEvent).
boolean	hasFocus()           Returns true if this Component is the focus owner.
void	hide()           Deprecated. As of JDK version 1.1, replaced by setVisible(boolean).
boolean	imageUpdate(Image img, int infoflags, int x, int y, int w, int h)           Repaints the component when the image has changed.
boolean	inside(int x, int y)           Deprecated. As of JDK version 1.1, replaced by contains(int, int).
void	invalidate()           Invalidates this component.
boolean	isBackgroundSet()           Returns whether the background color has been explicitly set for this Component.
boolean	isCursorSet()           Returns whether the cursor has been explicitly set for this Component.
boolean	isDisplayable()           Determines whether this component is displayable.
boolean	isDoubleBuffered()           Returns true if this component is painted to an offscreen image ("buffer") that's copied to the screen later.
boolean	isEnabled()           Determines whether this component is enabled.
boolean	isFocusable()           Returns whether this Component can be focused.
boolean	isFocusCycleRoot(Container container)           Returns whether the specified Container is the focus cycle root of this Component's focus traversal cycle.
boolean	isFocusOwner()           Returns true if this Component is the focus owner.
boolean	isFocusTraversable()           Deprecated. As of 1.4, replaced by isFocusable().
boolean	isFontSet()           Returns whether the font has been explicitly set for this Component.
boolean	isForegroundSet()           Returns whether the foreground color has been explicitly set for this Component.
boolean	isLightweight()           A lightweight component doesn't have a native toolkit peer.
boolean	isMaximumSizeSet()           Returns true if the maximum size has been set to a non-null value otherwise returns false.
boolean	isMinimumSizeSet()           Returns whether or not setMinimumSize has been invoked with a non-null value.
boolean	isOpaque()           Returns true if this component is completely opaque, returns false by default.
boolean	isPreferredSizeSet()           Returns true if the preferred size has been set to a non-null value otherwise returns false.
boolean	isShowing()           Determines whether this component is showing on screen.
boolean	isValid()           Determines whether this component is valid.
boolean	isVisible()           Determines whether this component should be visible when its parent is visible.
boolean	keyDown(Event evt, int key)           Deprecated. As of JDK version 1.1, replaced by processKeyEvent(KeyEvent).
boolean	keyUp(Event evt, int key)           Deprecated. As of JDK version 1.1, replaced by processKeyEvent(KeyEvent).
void	layout()           Deprecated. As of JDK version 1.1, replaced by doLayout().
void	list()           Prints a listing of this component to the standard system output stream System.out.
void	list(PrintStream out)           Prints a listing of this component to the specified output stream.
void	list(PrintStream out, int indent)           Prints out a list, starting at the specified indentation, to the specified print stream.
void	list(PrintWriter out)           Prints a listing to the specified print writer.
void	list(PrintWriter out, int indent)           Prints out a list, starting at the specified indentation, to the specified print writer.
Component	locate(int x, int y)           Deprecated. As of JDK version 1.1, replaced by getComponentAt(int, int).
Point	location()           Deprecated. As of JDK version 1.1, replaced by getLocation().
boolean	lostFocus(Event evt, Object what)           Deprecated. As of JDK version 1.1, replaced by processFocusEvent(FocusEvent).
Dimension	minimumSize()           Deprecated. As of JDK version 1.1, replaced by getMinimumSize().
boolean	mouseDown(Event evt, int x, int y)           Deprecated. As of JDK version 1.1, replaced by processMouseEvent(MouseEvent).
boolean	mouseDrag(Event evt, int x, int y)           Deprecated. As of JDK version 1.1, replaced by processMouseMotionEvent(MouseEvent).
boolean	mouseEnter(Event evt, int x, int y)           Deprecated. As of JDK version 1.1, replaced by processMouseEvent(MouseEvent).
boolean	mouseExit(Event evt, int x, int y)           Deprecated. As of JDK version 1.1, replaced by processMouseEvent(MouseEvent).
boolean	mouseMove(Event evt, int x, int y)           Deprecated. As of JDK version 1.1, replaced by processMouseMotionEvent(MouseEvent).
boolean	mouseUp(Event evt, int x, int y)           Deprecated. As of JDK version 1.1, replaced by processMouseEvent(MouseEvent).
void	move(int x, int y)           Deprecated. As of JDK version 1.1, replaced by setLocation(int, int).
void	nextFocus()           Deprecated. As of JDK version 1.1, replaced by transferFocus().
void	paint(Graphics g)           Paints this component.
void	paintAll(Graphics g)           Paints this component and all of its subcomponents.
protected  String	paramString()           Returns a string representing the state of this component.
boolean	postEvent(Event e)           Deprecated. As of JDK version 1.1, replaced by dispatchEvent(AWTEvent).
Dimension	preferredSize()           Deprecated. As of JDK version 1.1, replaced by getPreferredSize().
boolean	prepareImage(Image image, ImageObserver observer)           Prepares an image for rendering on this component.
boolean	prepareImage(Image image, int width, int height, ImageObserver observer)           Prepares an image for rendering on this component at the specified width and height.
void	print(Graphics g)           Prints this component.
void	printAll(Graphics g)           Prints this component and all of its subcomponents.
protected  void	processComponentEvent(ComponentEvent e)           Processes component events occurring on this component by dispatching them to any registered ComponentListener objects.
protected  void	processEvent(AWTEvent e)           Processes events occurring on this component.
protected  void	processFocusEvent(FocusEvent e)           Processes focus events occurring on this component by dispatching them to any registered FocusListener objects.
protected  void	processHierarchyBoundsEvent(HierarchyEvent e)           Processes hierarchy bounds events occurring on this component by dispatching them to any registered HierarchyBoundsListener objects.
protected  void	processHierarchyEvent(HierarchyEvent e)           Processes hierarchy events occurring on this component by dispatching them to any registered HierarchyListener objects.
protected  void	processInputMethodEvent(InputMethodEvent e)           Processes input method events occurring on this component by dispatching them to any registered InputMethodListener objects.
protected  void	processKeyEvent(KeyEvent e)           Processes key events occurring on this component by dispatching them to any registered KeyListener objects.
protected  void	processMouseEvent(MouseEvent e)           Processes mouse events occurring on this component by dispatching them to any registered MouseListener objects.
protected  void	processMouseMotionEvent(MouseEvent e)           Processes mouse motion events occurring on this component by dispatching them to any registered MouseMotionListener objects.
protected  void	processMouseWheelEvent(MouseWheelEvent e)           Processes mouse wheel events occurring on this component by dispatching them to any registered MouseWheelListener objects.
void	remove(MenuComponent popup)           Removes the specified popup menu from the component.
void	removeComponentListener(ComponentListener l)           Removes the specified component listener so that it no longer receives component events from this component.
void	removeFocusListener(FocusListener l)           Removes the specified focus listener so that it no longer receives focus events from this component.
void	removeHierarchyBoundsListener(HierarchyBoundsListener l)           Removes the specified hierarchy bounds listener so that it no longer receives hierarchy bounds events from this component.
void	removeHierarchyListener(HierarchyListener l)           Removes the specified hierarchy listener so that it no longer receives hierarchy changed events from this component.
void	removeInputMethodListener(InputMethodListener l)           Removes the specified input method listener so that it no longer receives input method events from this component.
void	removeKeyListener(KeyListener l)           Removes the specified key listener so that it no longer receives key events from this component.
void	removeMouseListener(MouseListener l)           Removes the specified mouse listener so that it no longer receives mouse events from this component.
void