java.awt

Class EventQueue

Known Direct Subclasses:
XEventQueue

public class EventQueue
extends Object

This class manages a queue of AWTEvent objects that are posted to it. The AWT system uses only one event queue for all events.

Constructor Summary

EventQueue()
Initializes a new instance of EventQueue.

Method Summary

protected void
dispatchEvent(AWTEvent evt)
Dispatches an event.
static AWTEvent
getCurrentEvent()
Return the event currently being dispatched by the event dispatch thread.
static long
getMostRecentEventTime()
Returns the timestamp of the most recent event that had a timestamp, or the initialization time of the event queue if no events have been fired.
AWTEvent
getNextEvent()
Returns the next event in the queue.
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)
This arranges for runnable to have its run method called in the dispatch thread of the EventQueue.
static boolean
isDispatchThread()
Return true if the current thread is the current AWT event dispatch thread.
AWTEvent
peekEvent()
Returns the next event in the queue without removing it from the queue.
AWTEvent
peekEvent(int id)
Returns the next event in the queue that has the specified id without removing it from the queue.
protected void
pop()
Transfer any pending events from this queue back to the parent queue that was previously push()ed.
void
postEvent(AWTEvent evt)
Posts a new event to the queue.
void
push(EventQueue newEventQueue)
Allows a custom EventQueue implementation to replace this one.

Methods inherited from class java.lang.Object

clone, equals, extends Object> getClass, finalize, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Details

EventQueue

public EventQueue()
Initializes a new instance of EventQueue.

Method Details

dispatchEvent

protected void dispatchEvent(AWTEvent evt)
Dispatches 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.
Throws:
NullPointerException - If event is null.

getCurrentEvent

public static AWTEvent getCurrentEvent()
Return the event currently being dispatched by the event dispatch thread. If the current thread is not the event dispatch thread, this method returns null.
Since:
1.4

getMostRecentEventTime

public static long getMostRecentEventTime()
Returns the timestamp of the most recent event that had a timestamp, or the initialization time of the event queue if no events have been fired. At present, only InputEvents, ActionEvents, InputMethodEvents, and InvocationEvents have timestamps, but this may be added to other events in future versions. If this is called by the event dispatching thread, it can be any (sequential) value, but to other threads, the safest bet is to return System.currentTimeMillis().
Returns:
the most recent timestamp
Since:
1.4

getNextEvent

public AWTEvent getNextEvent()
            throws InterruptedException
Returns the next event in the queue. This method will block until an event is available or until the thread is interrupted.
Returns:
The next event in the queue.
Throws:
InterruptedException - If this thread is interrupted while waiting for an event to be posted to the queue.

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.
Throws:
InterruptedException - If another thread has interrupted this thread.
InvocationTargetException - If an exception is thrown when running runnable.
Since:
1.2

invokeLater

public static void invokeLater(Runnable runnable)
This arranges for runnable to have its run method called in the dispatch thread of the EventQueue. This will happen after all pending events are processed.
Since:
1.2

isDispatchThread

public static boolean isDispatchThread()
Return true if the current thread is the current AWT event dispatch thread.

peekEvent

public AWTEvent peekEvent()
Returns the next event in the queue without removing it from the queue. This method will block until an event is available or until the thread is interrupted.
Returns:
The next event in the queue.

peekEvent

public AWTEvent peekEvent(int id)
Returns the next event in the queue that has the specified id without removing it from the queue. This method will block until an event is available or until the thread is interrupted.
Parameters:
id - The event id to return.
Returns:
The next event in the queue.

pop

protected void pop()
            throws EmptyStackException
Transfer any pending events from this queue back to the parent queue that was previously push()ed. Event dispatch from this queue is suspended.
Throws:
EmptyStackException - If no previous push was made on this EventQueue.

postEvent

public void postEvent(AWTEvent evt)
Posts a new event to the queue.
Parameters:
evt - The event to post to the queue.
Throws:
NullPointerException - If event is null.

push

public void push(EventQueue newEventQueue)
Allows a custom EventQueue implementation to replace this one. All pending events are transferred to the new queue. Calls to postEvent, getNextEvent, and peekEvent and others are forwarded to the pushed queue until it is removed with a pop().
Throws:
NullPointerException - if newEventQueue is null.

EventQueue.java -- Copyright (C) 1999, 2000, 2001, 2002, 2003, 2005 Free Software Foundation This file is part of GNU Classpath. GNU Classpath is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2, or (at your option) any later version. GNU Classpath is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with GNU Classpath; see the file COPYING. If not, write to the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA. Linking this library statically or dynamically with other modules is making a combined work based on this library. Thus, the terms and conditions of the GNU General Public License cover the whole combination. As a special exception, the copyright holders of this library give you permission to link this library with independent modules to produce an executable, regardless of the license terms of these independent modules, and to copy and distribute the resulting executable under terms of your choice, provided that you also meet, for each linked independent module, the terms and conditions of the license of that module. An independent module is a module which is not derived from or based on this library. If you modify this library, you may extend this exception to your version of the library, but you are not obligated to do so. If you do not wish to do so, delete this exception statement from your version.