java.awt
Class EventQueue

java.lang.Object
  java.awt.EventQueue

public class EventQueue
extends Object

EventQueue is a platform-independent class that queues events, both from the underlying peer classes and from trusted application classes. There is only one EventQueue for each AppContext.

Since:

1.1

Constructor Summary

EventQueue()

Method Summary

protected void	dispatchEvent(AWTEvent event) Dispatch an event.
static AWTEvent	getCurrentEvent() Returns the the event currently being dispatched by the EventQueue associated with the calling thread.
static long	getMostRecentEventTime()
AWTEvent	getNextEvent() Remove an event from the EventQueue and return it.
static void	invokeAndWait(Runnable runnable) Causes runnable to have its run() method called in the dispatch thread of the EventQueue.
static void	invokeLater(Runnable runnable) Causes runnable to have its run() method called in the dispatch thread of the EventQueue.
static boolean	isDispatchThread() Returns true if the calling thread is the current AWT EventQueue's dispatch thread.
AWTEvent	peekEvent() Return the first event on the EventQueue without removing it.
AWTEvent	peekEvent(int id) Return the first event with the specified id, if any.
protected void	pop() Stop dispatching events using this EventQueue instance.
void	postEvent(AWTEvent theEvent) Post a 1.1-style event to the EventQueue.
void	push(EventQueue newEventQueue) Replace the existing EventQueue with the specified one.

Methods inherited from class java.lang.Object

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

Constructor Detail

EventQueue

public EventQueue()

Method Detail

postEvent

public void postEvent(AWTEvent theEvent)

Post a 1.1-style event to the EventQueue. If there is an existing event on the queue with the same ID and event source, the source Component's coalesceEvents method will be called.

Parameters:

theEvent - an instance of java.awt.AWTEvent, or a subclass of it.

getNextEvent

public AWTEvent getNextEvent()
                      throws InterruptedException

Remove an event from the EventQueue and return it. This method will block until an event has been posted by another thread.

Returns:

the next AWTEvent

Throws:

InterruptedException - if another thread has interrupted this thread.

peekEvent

public AWTEvent peekEvent()

Return the first event on the EventQueue without removing it.

Returns:

the first event

peekEvent

public AWTEvent peekEvent(int id)

Return the first event with the specified id, if any.

Parameters:

id - the id of the type of event desired.

Returns:

the first event of the specified id

dispatchEvent

protected void dispatchEvent(AWTEvent event)

Dispatch an event. The manner in which the event is dispatched depends upon the type of the event and the type of the event's source object:

Event Type	Source Type	Dispatched To
ActiveEvent	Any	event.dispatch()
Other	Component	source.dispatchEvent(AWTEvent)
Other	MenuComponent	source.dispatchEvent(AWTEvent)
Other	Other	No action (ignored)

Parameters:

theEvent - an instance of java.awt.AWTEvent, or a subclass of it.

push

public void push(EventQueue newEventQueue)

Replace the existing EventQueue with the specified one. Any pending events are transferred to the new EventQueue for processing by it.

Parameters:

an - EventQueue (or subclass thereof) instance to be used.

See Also:

pop()

pop

protected void pop()
            throws EmptyStackException

Stop dispatching events using this EventQueue instance. Any pending events are transferred to the previous EventQueue for processing by it.

Throws:

if - no previous push was made on this EventQueue.

EmptyStackException

See Also:

push(java.awt.EventQueue)

isDispatchThread

public static boolean isDispatchThread()

Returns true if the calling thread is the current AWT EventQueue's dispatch thread. Use this call the ensure that a given task is being executed (or not being) on the current AWT EventDispatchThread.

Returns:

true if running on the current AWT EventQueue's dispatch thread.

invokeLater

public static void invokeLater(Runnable runnable)

Causes runnable to have its run() method called in the dispatch thread of the EventQueue. This will happen after all pending events are processed.

Parameters:

runnable - the Runnable whose run() method should be executed synchronously on the EventQueue

Since:

1.2

See Also:

invokeAndWait(java.lang.Runnable)

invokeAndWait

public static void invokeAndWait(Runnable runnable)
                          throws InterruptedException,
                                 InvocationTargetException

Causes runnable to have its run() method called in the dispatch thread of the EventQueue. This will happen after all pending events are processed. The call blocks until this has happened. This method will throw an Error if called from the event dispatcher thread.

Parameters:

runnable - the Runnable whose run() method should be executed synchronously on the EventQueue

Throws:

InterruptedException - if another thread has interrupted this thread

InvocationTargetException - if an exception is thrown when running runnable

Since:

1.2

See Also:

invokeLater(java.lang.Runnable)

getMostRecentEventTime

public static long getMostRecentEventTime()

getCurrentEvent

public static AWTEvent getCurrentEvent()

Returns the the event currently being dispatched by the EventQueue associated with the calling thread. This is useful if a method needs access to the event, but was not designed to receive a reference to it as an argument. Note that this method should only be invoked from an application's event dispatching thread. If this method is invoked from another thread, null will be returned.

Returns:

the event currently being dispatched, or null if this method is invoked on a thread other than an event dispatching thread

Since:

1.4