java.awt
Class Component

java.lang.Object
  |
  +--java.awt.Component

All Implemented Interfaces:

java.awt.image.ImageObserver

Direct Known Subclasses:

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

public abstract class Component

extends Object

implements java.awt.image.ImageObserver

A generic Abstract Window Toolkit component.

Field Summary

Fields inherited from interface java.awt.image.ImageObserver

ABORT, ALLBITS, ERROR, FRAMEBITS, HEIGHT, PROPERTIES, SOMEBITS, WIDTH

Method Summary

boolean	action(Event evt, Object what) Called if an action occurs in the Component.
void	addNotify() Notifies the Component to create a peer.
Rectangle	bounds() Returns the current bounds of this component.
int	checkImage(Image image, java.awt.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, java.awt.image.ImageObserver observer) Returns the status of the construction of a scaled screen representation of the specified image.
Image	createImage(java.awt.image.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.
void	deliverEvent(Event e) Delivers an event to this component or one of its sub components.
void	disable() Disables a component.
void	enable() Enables a component.
void	enable(boolean cond) Conditionally enables a component.
Color	getBackground() Gets the background color.
java.awt.image.ColorModel	getColorModel() Gets the ColorModel used to display the component on the output device.
Font	getFont() Gets the font of the component.
FontMetrics	getFontMetrics(Font font) Gets the font metrics for this component.
Color	getForeground() Gets the foreground color.
Graphics	getGraphics() Gets a Graphics context for this component.
Container	getParent() Gets the parent of the component.
java.awt.peer.ComponentPeer	getPeer() Gets the peer of the component.
Toolkit	getToolkit() Gets the toolkit of the component.
boolean	gotFocus(Event evt, Object what) Indicates that this component has received the input focus.
boolean	handleEvent(Event evt) Handles the event.
void	hide() Hides the component.
boolean	imageUpdate(Image img, int flags, int x, int y, int w, int h) Repaints the component when the image has changed.
boolean	inside(int x, int y) Checks whether a specified x,y location is "inside" this Component, where x and y are defined to be relative to the coordinate system of this component.
void	invalidate() Invalidates the component.
boolean	isEnabled() Checks if this Component is enabled.
boolean	isShowing() Checks if this Component is showing on screen.
boolean	isValid() Checks if this Component is valid.
boolean	isVisible() Checks if this Component is visible.
boolean	keyDown(Event evt, int key) Called if a character is pressed.
boolean	keyUp(Event evt, int key) Called if a character is released.
void	layout() Lays out the component.
void	list() Prints a listing to a print stream.
void	list(PrintStream out) Prints a listing to the specified print out stream.
void	list(PrintStream out, int indent) Prints out a list, starting at the specified indention, to the specified print stream.
Component	locate(int x, int y) Returns the component or subcomponent that contains the x,y location.
Point	location() Returns the current location of this component.
boolean	lostFocus(Event evt, Object what) Indicates that this component has lost the input focus.
Dimension	minimumSize() Returns the minimum size of this component.
boolean	mouseDown(Event evt, int x, int y) Called if the mouse is down.
boolean	mouseDrag(Event evt, int x, int y) Called if the mouse is dragged (the mouse button is down).
boolean	mouseEnter(Event evt, int x, int y) Called when the mouse enters the component.
boolean	mouseExit(Event evt, int x, int y) Called when the mouse exits the component.
boolean	mouseMove(Event evt, int x, int y) Called if the mouse moves (the mouse button is up).
boolean	mouseUp(Event evt, int x, int y) Called if the mouse is up.
void	move(int x, int y) Moves the Component to a new location.
void	nextFocus() Moves the focus to the next component.
void	paint(Graphics g) Paints the component.
void	paintAll(Graphics g) Paints the component and its subcomponents.
protected String	paramString() Returns the parameter String of this Component.
boolean	postEvent(Event e) Posts an event to this component.
Dimension	preferredSize() Returns the preferred size of this component.
boolean	prepareImage(Image image, java.awt.image.ImageObserver observer) Prepares an image for rendering on this Component.
boolean	prepareImage(Image image, int width, int height, java.awt.image.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 the component and its subcomponents.
void	removeNotify() Notifies the Component to destroy the peer.
void	repaint() Repaints the component.
void	repaint(int x, int y, int width, int height) Repaints part of the component.
void	repaint(long tm) Repaints the component.
void	repaint(long tm, int x, int y, int width, int height) Repaints part of the component.
void	requestFocus() Requests the input focus.
void	reshape(int x, int y, int width, int height) Reshapes the Component to the specified bounding box.
void	resize(Dimension d) Resizes the Component to the specified dimension.
void	resize(int width, int height) Resizes the Component to the specified width and height.
void	setBackground(Color c) Sets the background color.
void	setFont(Font f) Sets the font of the component.
void	setForeground(Color c) Sets the foreground color.
void	show() Shows the component.
void	show(boolean cond) Conditionally shows the component.
Dimension	size() Returns the current size of this component.
String	toString() Returns the String representation of this Component's values.
void	update(Graphics g) Updates the component.
void	validate() Validates a component.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Method Detail

getParent

public Container getParent()

Gets the parent of the component.

getPeer

public java.awt.peer.ComponentPeer getPeer()

Gets the peer of the component.

getToolkit

public Toolkit getToolkit()

Gets the toolkit of the component. This toolkit is used to create the peer for this component. Note that the Frame which contains a Component controls which toolkit is used so if the Component has not yet been added to a Frame or if it is later moved to a different Frame, the toolkit it uses may change.

isValid

public boolean isValid()

Checks if this Component is valid. Components are invalidated when they are first shown on the screen.

See Also:

validate(), invalidate()

isVisible

public boolean isVisible()

Checks if this Component is visible. Components are initially visible (with the exception of top level components such as Frame).

See Also:

show(), hide()

isShowing

public boolean isShowing()

Checks if this Component is showing on screen. This means that the component must be visible, and it must be in a container that is visible and showing.

See Also:

show(), hide()

isEnabled

public boolean isEnabled()

Checks if this Component is enabled. Components are initially enabled.

See Also:

enable(), disable()

location

public Point location()

Returns the current location of this component. The location will be in the parent's coordinate space.

See Also:

move(int, int)

size

public Dimension size()

Returns the current size of this component.

See Also:

resize(int, int)

bounds

public Rectangle bounds()

Returns the current bounds of this component.

See Also:

reshape(int, int, int, int)

enable

public void enable()

Enables a component.

See Also:

isEnabled(), disable()

enable

public void enable(boolean cond)

Conditionally enables a component.

Parameters:

cond - if true, enables component; disables otherwise.

See Also:

enable(), disable()

disable

public void disable()

Disables a component.

See Also:

isEnabled(), enable()

show

public void show()

Shows the component.

See Also:

isVisible(), hide()

show

public void show(boolean cond)

Conditionally shows the component.

Parameters:

cond - if true, it shows the component; hides otherwise.

See Also:

show(), hide()

hide

public void hide()

Hides the component.

See Also:

isVisible(), hide()

getForeground

public Color getForeground()

Gets the foreground color. If the component does not have a foreground color, the foreground color of its parent is returned.

See Also:

setForeground(java.awt.Color)

setForeground

public void setForeground(Color c)

Sets the foreground color.

Parameters:

c - the Color

See Also:

getForeground()

getBackground

public Color getBackground()

Gets the background color. If the component does not have a background color, the background color of its parent is returned.

See Also:

setBackground(java.awt.Color)

setBackground

public void setBackground(Color c)

Sets the background color.

Parameters:

c - the Color

See Also:

getBackground()

getFont

public Font getFont()

Gets the font of the component. If the component does not have a font, the font of its parent is returned.

See Also:

setFont(java.awt.Font)

setFont

public void setFont(Font f)

Sets the font of the component.

Parameters:

f - the font

See Also:

getFont()

getColorModel

public java.awt.image.ColorModel getColorModel()

Gets the ColorModel used to display the component on the output device.

See Also:

ColorModel

move

public void move(int x,
                 int y)

Moves the Component to a new location. The x and y coordinates are in the parent's coordinate space.

Parameters:

x - the x coordinate

y - the y coordinate

See Also:

location(), reshape(int, int, int, int)

resize

public void resize(int width,
                   int height)

Resizes the Component to the specified width and height.

Parameters:

width - the width of the component

height - the height of the component

See Also:

size(), reshape(int, int, int, int)

resize

public void resize(Dimension d)

Resizes the Component to the specified dimension.

Parameters:

d - the component dimension

See Also:

size(), reshape(int, int, int, int)

reshape

public void reshape(int x,
                    int y,
                    int width,
                    int height)

Reshapes the Component to the specified bounding box.

Parameters:

x - the x coordinate

y - the y coordinate

width - the width of the component

height - the height of the component

See Also:

bounds(), move(int, int), resize(int, int)

preferredSize

public Dimension preferredSize()

Returns the preferred size of this component.

See Also:

minimumSize(), LayoutManager

minimumSize

public Dimension minimumSize()

Returns the minimum size of this component.

See Also:

preferredSize(), LayoutManager

layout

public void layout()

Lays out the component. This is usually called when the component is validated.

See Also:

validate(), LayoutManager

validate

public void validate()

Validates a component.

See Also:

invalidate(), layout(), LayoutManager

invalidate

public void invalidate()

Invalidates the component. The component and all parents above it are marked as needing to be laid out.

See Also:

validate(), layout(), LayoutManager

getGraphics

public Graphics getGraphics()

Gets a Graphics context for this component. This method will return null if the component is currently not on the screen.

See Also:

paint(java.awt.Graphics)

getFontMetrics

public FontMetrics getFontMetrics(Font font)

Gets the font metrics for this component.

Parameters:

font - the font

See Also:

getFont()

paint

public void paint(Graphics g)

Paints the component.

Parameters:

g - the specified Graphics window

See Also:

update(java.awt.Graphics)

update

public void update(Graphics g)

Updates the component. This method is called in response to a call to repaint. You can assume that the background is not cleared.

Parameters:

g - the specified Graphics window

See Also:

paint(java.awt.Graphics), repaint()

paintAll

public void paintAll(Graphics g)

Paints the component and its subcomponents.

Parameters:

g - the specified Graphics window

See Also:

paint(java.awt.Graphics)

repaint

public void repaint()

Repaints the component. This will result in a call to update as soon as possible.

See Also:

paint(java.awt.Graphics)

repaint

public void repaint(long tm)

Repaints the component. This will result in a call to update within tm milliseconds.

Parameters:

tm - maximum time in milliseconds before update

See Also:

paint(java.awt.Graphics)

repaint

public void repaint(int x,
                    int y,
                    int width,
                    int height)

Repaints part of the component. This will result in a call to update as soon as possible.

Parameters:

x - the x coordinate

y - the y coordinate

width - the width

height - the height

See Also:

repaint()

repaint

public void repaint(long tm,
                    int x,
                    int y,
                    int width,
                    int height)

Repaints part of the component. This will result in a call to update width tm millseconds.

Parameters:

tm - maximum time in milliseconds before update

x - the x coordinate

y - the y coordinate

width - the width

height - the height

See Also:

repaint()

print

public void print(Graphics g)

Prints this component. The default implementation of this method calls paint.

Parameters:

g - the specified Graphics window

See Also:

paint(java.awt.Graphics)

printAll

public void printAll(Graphics g)

Prints the component and its subcomponents.

Parameters:

g - the specified Graphics window

See Also:

print(java.awt.Graphics)

imageUpdate

public boolean imageUpdate(Image img,
                           int flags,
                           int x,
                           int y,
                           int w,
                           int h)

Repaints the component when the image has changed.

Specified by:

imageUpdate in interface java.awt.image.ImageObserver

Returns:

true if image has changed; false otherwise.

createImage

public Image createImage(java.awt.image.ImageProducer producer)

Creates an image from the specified image producer.

Parameters:

producer - the image producer

createImage

public Image createImage(int width,
                         int height)

Creates an off-screen drawable Image to be used for double buffering.

Parameters:

width - the specified width

height - the specified height

prepareImage

public boolean prepareImage(Image image,
                            java.awt.image.ImageObserver observer)

Prepares an image for rendering on this Component. The image data is downloaded asynchronously in another thread and the appropriate screen representation of the image is generated.

Parameters:

image - the Image to prepare a screen representation for

observer - the ImageObserver object to be notified as the image is being prepared

Returns:

true if the image has already been fully prepared

See Also:

ImageObserver

prepareImage

public boolean prepareImage(Image image,
                            int width,
                            int height,
                            java.awt.image.ImageObserver observer)

Prepares an image for rendering on this Component at the specified width and height. The image data is downloaded asynchronously in another thread and an appropriately scaled screen representation of the image is generated.

Parameters:

image - the Image to prepare a screen representation for

width - the width of the desired screen representation

height - the height of the desired screen representation

observer - the ImageObserver object to be notified as the image is being prepared

Returns:

true if the image has already been fully prepared

See Also:

ImageObserver

checkImage

public int checkImage(Image image,
                      java.awt.image.ImageObserver observer)

Returns the status of the construction of a screen representation of the specified image. This method does not cause the image to begin loading. Use the prepareImage method to force the loading of an image.

Parameters:

image - the Image to check the status of

observer - the ImageObserver object to be notified as the image is being prepared

Returns:

the boolean OR of the ImageObserver flags for the data that is currently available

See Also:

ImageObserver, prepareImage(java.awt.Image, java.awt.image.ImageObserver)

checkImage

public int checkImage(Image image,
                      int width,
                      int height,
                      java.awt.image.ImageObserver observer)

Returns the status of the construction of a scaled screen representation of the specified image. This method does not cause the image to begin loading, use the prepareImage method to force the loading of an image.

Parameters:

image - the Image to check the status of

width - the width of the scaled version to check the status of

height - the height of the scaled version to check the status of

observer - the ImageObserver object to be notified as the image is being prepared

Returns:

the boolean OR of the ImageObserver flags for the data that is currently available

See Also:

ImageObserver, prepareImage(java.awt.Image, java.awt.image.ImageObserver)

inside

public boolean inside(int x,
                      int y)

Checks whether a specified x,y location is "inside" this Component, where x and y are defined to be relative to the coordinate system of this component.

Parameters:

x - the x coordinate

y - the y coordinate

See Also:

locate(int, int)

locate

public Component locate(int x,
                        int y)

Returns the component or subcomponent that contains the x,y location.

Parameters:

x - the x coordinate

y - the y coordinate

See Also:

inside(int, int)

deliverEvent

public void deliverEvent(Event e)

Delivers an event to this component or one of its sub components.

Parameters:

e - the event

See Also:

handleEvent(java.awt.Event), postEvent(java.awt.Event)

postEvent

public boolean postEvent(Event e)

Posts an event to this component. This will result in a call to handleEvent. If handleEvent returns false the event is passed on to the parent of this component.

Parameters:

e - the event

See Also:

handleEvent(java.awt.Event), deliverEvent(java.awt.Event)

handleEvent

public boolean handleEvent(Event evt)

Handles the event. Returns true if the event is handled and should not be passed to the parent of this component. The default event handler calls some helper methods to make life easier on the programmer.

Parameters:

evt - the event

See Also:

mouseEnter(java.awt.Event, int, int), mouseExit(java.awt.Event, int, int), mouseMove(java.awt.Event, int, int), mouseDown(java.awt.Event, int, int), mouseDrag(java.awt.Event, int, int), mouseUp(java.awt.Event, int, int), keyDown(java.awt.Event, int), action(java.awt.Event, java.lang.Object)

mouseDown

public boolean mouseDown(Event evt,
                         int x,
                         int y)

Called if the mouse is down.

Parameters:

evt - the event

x - the x coordinate

y - the y coordinate

See Also:

handleEvent(java.awt.Event)

mouseDrag

public boolean mouseDrag(Event evt,
                         int x,
                         int y)

Called if the mouse is dragged (the mouse button is down).

Parameters:

evt - the event

x - the x coordinate

y - the y coordinate

See Also:

handleEvent(java.awt.Event)

mouseUp

public boolean mouseUp(Event evt,
                       int x,
                       int y)

Called if the mouse is up.

Parameters:

evt - the event

x - the x coordinate

y - the y coordinate

See Also:

handleEvent(java.awt.Event)

mouseMove

public boolean mouseMove(Event evt,
                         int x,
                         int y)

Called if the mouse moves (the mouse button is up).

Parameters:

evt - the event

x - the x coordinate

y - the y coordinate

See Also:

handleEvent(java.awt.Event)

mouseEnter

public boolean mouseEnter(Event evt,
                          int x,
                          int y)

Called when the mouse enters the component.

Parameters:

evt - the event

x - the x coordinate

y - the y coordinate

See Also:

handleEvent(java.awt.Event)

mouseExit

public boolean mouseExit(Event evt,
                         int x,
                         int y)

Called when the mouse exits the component.

Parameters:

evt - the event

x - the x coordinate

y - the y coordinate

See Also:

handleEvent(java.awt.Event)

keyDown

public boolean keyDown(Event evt,
                       int key)

Called if a character is pressed.

Parameters:

evt - the event

key - the key that's pressed

See Also:

handleEvent(java.awt.Event)

keyUp

public boolean keyUp(Event evt,
                     int key)

Called if a character is released.

Parameters:

evt - the event

key - the key that's released

See Also:

handleEvent(java.awt.Event)

action

public boolean action(Event evt,
                      Object what)

Called if an action occurs in the Component.

Parameters:

evt - the event

what - the action that's occuring

See Also:

handleEvent(java.awt.Event)

addNotify

public void addNotify()

Notifies the Component to create a peer.

See Also:

getPeer(), removeNotify()

removeNotify

public void removeNotify()

Notifies the Component to destroy the peer.

See Also:

getPeer(), addNotify()

gotFocus

public boolean gotFocus(Event evt,
                        Object what)

Indicates that this component has received the input focus.

See Also:

requestFocus(), lostFocus(java.awt.Event, java.lang.Object)

lostFocus

public boolean lostFocus(Event evt,
                         Object what)

Indicates that this component has lost the input focus.

See Also:

requestFocus(), gotFocus(java.awt.Event, java.lang.Object)

requestFocus

public void requestFocus()

Requests the input focus. The gotFocus() method will be called if this method is successful.

See Also:

gotFocus(java.awt.Event, java.lang.Object)

nextFocus

public void nextFocus()

Moves the focus to the next component.

See Also:

requestFocus(), gotFocus(java.awt.Event, java.lang.Object)

paramString

protected String paramString()

Returns the parameter String of this Component.

toString

public String toString()

Returns the String representation of this Component's values.

Overrides:

toString in class Object

list

public void list()

Prints a listing to a print stream.

list

public void list(PrintStream out)

Prints a listing to the specified print out stream.

Parameters:

out - the Stream name

list

public void list(PrintStream out,
                 int indent)

Prints out a list, starting at the specified indention, to the specified print stream.

Parameters:

out - the Stream name

indent - the start of the list