Class Button
- All Implemented Interfaces:
ImageObserver
,MenuContainer
,Serializable
,Accessible
Quit
" button as it appears
under the Solaris operating system:
The first view shows the button as it appears normally. The second view shows the button when it has input focus. Its outline is darkened to let the user know that it is an active object. The third view shows the button when the user clicks the mouse over the button, and thus requests that an action be performed.
The gesture of clicking on a button with the mouse
is associated with one instance of ActionEvent
,
which is sent out when the mouse is both pressed and released
over the button. If an application is interested in knowing
when the button has been pressed but not released, as a separate
gesture, it can specialize processMouseEvent
,
or it can register itself as a listener for mouse events by
calling addMouseListener
. Both of these methods are
defined by Component
, the abstract superclass of
all components.
When a button is pressed and released, AWT sends an instance
of ActionEvent
to the button, by calling
processEvent
on the button. The button's
processEvent
method receives all events
for the button; it passes an action event along by
calling its own processActionEvent
method.
The latter method passes the action event on to any action
listeners that have registered an interest in action
events generated by this button.
If an application wants to perform some action based on
a button being pressed and released, it should implement
ActionListener
and register the new listener
to receive events from this button, by calling the button's
addActionListener
method. The application can
make use of the button's action command as a messaging protocol.
- Since:
- 1.0
- See Also:
-
Nested Class Summary
Modifier and TypeClassDescriptionprotected class
This class implements accessibility support for theButton
class.Nested classes/interfaces declared in class java.awt.Component
Component.AccessibleAWTComponent, Component.BaselineResizeBehavior, Component.BltBufferStrategy, Component.FlipBufferStrategy
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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
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Constructor Summary
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Method Summary
Modifier and TypeMethodDescriptionvoid
Adds the specified action listener to receive action events from this button.void
Creates the peer of the button.Gets theAccessibleContext
associated with thisButton
.Returns the command name of the action event fired by this button.Returns an array of all the action listeners registered on this button.getLabel()
Gets the label of this button.<T extends EventListener>
T[]getListeners
(Class<T> listenerType) Returns an array of all the objects currently registered asFooListener
s upon thisButton
.protected String
Returns a string representing the state of thisButton
.protected void
Processes action events occurring on this button by dispatching them to any registeredActionListener
objects.protected void
Processes events on this button.void
Removes the specified action listener so that it no longer receives action events from this button.void
setActionCommand
(String command) Sets the command name for the action event fired by this button.void
Sets the button's label to be the specified string.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, 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, paint, paintAll, postEvent, preferredSize, prepareImage, prepareImage, print, printAll, processComponentEvent, 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, update, validate
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Constructor Details
-
Button
Constructs a button with an empty string for its label.- Throws:
HeadlessException
- if GraphicsEnvironment.isHeadless() returns true- See Also:
-
Button
Constructs a button with the specified label.- Parameters:
label
- a string label for the button, ornull
for no label- Throws:
HeadlessException
- if GraphicsEnvironment.isHeadless() returns true- See Also:
-
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Method Details
-
addNotify
-
getLabel
Gets the label of this button.- Returns:
- the button's label, or
null
if the button has no label. - See Also:
-
setLabel
Sets the button's label to be the specified string.- Parameters:
label
- the new label, ornull
if the button has no label.- See Also:
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setActionCommand
Sets the command name for the action event fired by this button. By default this action command is set to match the label of the button.- Parameters:
command
- a string used to set the button's action command. If the string isnull
then the action command is set to match the label of the button.- Since:
- 1.1
- See Also:
-
getActionCommand
Returns the command name of the action event fired by this button. If the command name isnull
(default) then this method returns the label of the button.- Returns:
- the action command name (or label) for this button
-
addActionListener
Adds the specified action listener to receive action events from this button. Action events occur when a user presses or releases the mouse over this button. If l is null, no exception is thrown and no action is performed.Refer to AWT Threading Issues for details on AWT's threading model.
- Parameters:
l
- the action listener- Since:
- 1.1
- See Also:
-
removeActionListener
Removes the specified action listener so that it no longer receives action events from this button. Action events occur when a user presses or releases the mouse over this button. If l is null, no exception is thrown and no action is performed.Refer to AWT Threading Issues for details on AWT's threading model.
- Parameters:
l
- the action listener- Since:
- 1.1
- See Also:
-
getActionListeners
Returns an array of all the action listeners registered on this button.- Returns:
- all of this button's
ActionListener
s or an empty array if no action listeners are currently registered - Since:
- 1.4
- See Also:
-
getListeners
Returns an array of all the objects currently registered asFooListener
s upon thisButton
.FooListener
s are registered using theaddFooListener
method.You can specify the
listenerType
argument with a class literal, such asFooListener.class
. For example, you can query aButton b
for its action listeners with the following code:ActionListener[] als = (ActionListener[])(b.getListeners(ActionListener.class));
If no such listeners exist, this method returns an empty array.- Overrides:
getListeners
in classComponent
- Type Parameters:
T
- the type of the listeners- Parameters:
listenerType
- the type of listeners requested; this parameter should specify an interface that descends fromjava.util.EventListener
- Returns:
- an array of all objects registered as
FooListener
s on this button, or an empty array if no such listeners have been added - Throws:
ClassCastException
- iflistenerType
doesn't specify a class or interface that implementsjava.util.EventListener
- Since:
- 1.3
- See Also:
-
processEvent
Processes events on this button. If an event is an instance ofActionEvent
, this method invokes theprocessActionEvent
method. Otherwise, it invokesprocessEvent
on the superclass.Note that if the event parameter is
null
the behavior is unspecified and may result in an exception.- Overrides:
processEvent
in classComponent
- Parameters:
e
- the event- Since:
- 1.1
- See Also:
-
processActionEvent
Processes action events occurring on this button by dispatching them to any registeredActionListener
objects.This method is not called unless action events are enabled for this button. Action events are enabled when one of the following occurs:
- An
ActionListener
object is registered viaaddActionListener
. - Action events are enabled via
enableEvents
.
Note that if the event parameter is
null
the behavior is unspecified and may result in an exception.- Parameters:
e
- the action event- Since:
- 1.1
- See Also:
- An
-
paramString
Returns a string representing the state of thisButton
. This method is intended to be used only for debugging purposes, and the content and format of the returned string may vary between implementations. The returned string may be empty but may not benull
.- Overrides:
paramString
in classComponent
- Returns:
- the parameter string of this button
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getAccessibleContext
@BeanProperty(expert=true, description="The AccessibleContext associated with this Button.") public AccessibleContext getAccessibleContext()Gets theAccessibleContext
associated with thisButton
. For buttons, theAccessibleContext
takes the form of anAccessibleAWTButton
. A newAccessibleAWTButton
instance is created if necessary.- Specified by:
getAccessibleContext
in interfaceAccessible
- Overrides:
getAccessibleContext
in classComponent
- Returns:
- an
AccessibleAWTButton
that serves as theAccessibleContext
of thisButton
- Since:
- 1.3
-