EventDispatchThread is a package-private AWT class which takes
events off the EventQueue and dispatches them to the appropriate
AWT components.
The Thread starts a "permanent" event pump with a call to
pumpEvents(Conditional) in its run() method. Event handlers can choose to
block this event pump at any time, but should start a new pump (
a new EventDispatchThread) by again calling pumpEvents(Conditional). This
secondary event pump will exit automatically as soon as the Condtional
evaluate()s to false and an additional Event is pumped and dispatched.
| Method from java.awt.EventDispatchThread Detail: |
void addEventFilter(EventFilter filter) {
synchronized (eventFilters) {
if (!eventFilters.contains(filter)) {
if (filter instanceof ModalEventFilter) {
ModalEventFilter newFilter = (ModalEventFilter)filter;
int k = 0;
for (k = 0; k < eventFilters.size(); k++) {
EventFilter f = eventFilters.get(k);
if (f instanceof ModalEventFilter) {
ModalEventFilter cf = (ModalEventFilter)f;
if (cf.compareTo(newFilter) > 0) {
break;
}
}
}
eventFilters.add(k, filter);
modalFiltersCount++;
} else {
eventFilters.add(filter);
}
}
}
}
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EventQueue getEventQueue() {
return theQueue;
}
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boolean isDispatching(EventQueue eq) {
return theQueue.equals(eq);
}
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void pumpEvents(Conditional cond) {
pumpEvents(ANY_EVENT, cond);
}
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void pumpEvents(int id,
Conditional cond) {
pumpEventsForHierarchy(id, cond, null);
}
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void pumpEventsForFilter(Conditional cond,
EventFilter filter) {
pumpEventsForFilter(ANY_EVENT, cond, filter);
}
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void pumpEventsForFilter(int id,
Conditional cond,
EventFilter filter) {
addEventFilter(filter);
while (doDispatch && cond.evaluate()) {
if (isInterrupted() || !pumpOneEventForFilters(id)) {
doDispatch = false;
}
}
removeEventFilter(filter);
}
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void pumpEventsForHierarchy(Conditional cond,
Component modalComponent) {
pumpEventsForHierarchy(ANY_EVENT, cond, modalComponent);
}
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void pumpEventsForHierarchy(int id,
Conditional cond,
Component modalComponent) {
pumpEventsForFilter(id, cond, new HierarchyEventFilter(modalComponent));
}
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boolean pumpOneEventForFilters(int id) {
try {
AWTEvent event;
boolean eventOK;
do {
event = (id == ANY_EVENT)
? theQueue.getNextEvent()
: theQueue.getNextEvent(id);
eventOK = true;
synchronized (eventFilters) {
for (int i = eventFilters.size() - 1; i >= 0; i--) {
EventFilter f = eventFilters.get(i);
EventFilter.FilterAction accept = f.acceptEvent(event);
if (accept == EventFilter.FilterAction.REJECT) {
eventOK = false;
break;
} else if (accept == EventFilter.FilterAction.ACCEPT_IMMEDIATELY) {
break;
}
}
}
eventOK = eventOK && SunDragSourceContextPeer.checkEvent(event);
if (!eventOK) {
event.consume();
}
}
while (eventOK == false);
if (eventLog.isLoggable(Level.FINEST)) {
eventLog.log(Level.FINEST, "Dispatching: " + event);
}
theQueue.dispatchEvent(event);
return true;
}
catch (ThreadDeath death) {
return false;
}
catch (InterruptedException interruptedException) {
return false; // AppContext.dispose() interrupts all
// Threads in the AppContext
}
// Can get and throw only unchecked exceptions
catch (RuntimeException e) {
processException(e, modalFiltersCount > 0);
} catch (Error e) {
processException(e, modalFiltersCount > 0);
}
return true;
}
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void removeEventFilter(EventFilter filter) {
synchronized (eventFilters) {
if (eventFilters.contains(filter)) {
if (filter instanceof ModalEventFilter) {
modalFiltersCount--;
}
eventFilters.remove(filter);
}
}
}
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public void run() {
try {
pumpEvents(new Conditional() {
public boolean evaluate() {
return true;
}
});
} finally {
/*
* This synchronized block is to secure that the event dispatch
* thread won't die in the middle of posting a new event to the
* associated event queue. It is important because we notify
* that the event dispatch thread is busy after posting a new event
* to its queue, so the EventQueue.dispatchThread reference must
* be valid at that point.
*/
synchronized (theQueue) {
if (theQueue.getDispatchThread() == this) {
theQueue.detachDispatchThread();
}
/*
* Event dispatch thread dies in case of an uncaught exception.
* A new event dispatch thread for this queue will be started
* only if a new event is posted to it. In case if no more
* events are posted after this thread died all events that
* currently are in the queue will never be dispatched.
*/
/*
* Fix for 4648733. Check both the associated java event
* queue and the PostEventQueue.
*/
if (theQueue.peekEvent() != null ||
!SunToolkit.isPostEventQueueEmpty()) {
theQueue.initDispatchThread();
}
AWTAutoShutdown.getInstance().notifyThreadFree(this);
}
}
}
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public void stopDispatching() {
stopDispatchingImpl(true);
}
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void stopDispatchingImpl(boolean wait) {
// Note: We stop dispatching via a flag rather than using
// Thread.interrupt() because we can't guarantee that the wait()
// we interrupt will be EventQueue.getNextEvent()'s. -fredx 8-11-98
StopDispatchEvent stopEvent = new StopDispatchEvent();
// wait for the dispatcher to complete
if (Thread.currentThread() != this) {
// fix 4122683, 4128923
// Post an empty event to ensure getNextEvent is unblocked
//
// We have to use postEventPrivate instead of postEvent because
// EventQueue.pop calls EventDispatchThread.stopDispatching.
// Calling SunToolkit.flushPendingEvents in this case could
// lead to deadlock.
theQueue.postEventPrivate(stopEvent);
if (wait) {
try {
join();
} catch(InterruptedException e) {
}
}
} else {
stopEvent.dispatch();
}
synchronized (theQueue) {
if (theQueue.getDispatchThread() == this) {
theQueue.detachDispatchThread();
}
}
}
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public void stopDispatchingLater() {
stopDispatchingImpl(false);
}
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