Waiting for all Runnables submitted to the SWT UI stream with Display :: asyncExec () to complete

Question

Is there a way to wait for all Runnables represented in the UT SWT stream via asyncExec (...) to complete?

Background:

I have a lot of work to do, which, among other things, fires events that, in turn, send Runnables to the SWT UI thread through the asyncExec (...) Display instance method.

The progress of a long operation is shown in the ProgressMonitorDialog, and I would like to close the dialog only after the user interface thread has finished running Runnables.

Changing calls from asyncExec (...) to syncExec (...) is not a parameter, since the latter is undesirable when events are fired from other contexts.

Answer 1

org.eclipse.swt.widgets.Display.readAndDispatch() process the event from the event queue and will return false if more events are not processed. But you probably don't want to use this as it handles the event.

asyncExec(*) is a FIFO queue (although OS graphics events replace asyncExecs), so you could do most of your lengthy op processing and then put the final asyncExec in the queue:

 final boolean[] done = new boolean[1]; Runnable r = new Runnable() { public void run() { done[0] = true; } }; // now wait for the event somehow. The brute force method: while (!done[0]) { Thread.sleep(200); } 

In theory, all other asyncExecs generated from your long number will be finished by the time you get to the last.

EDIT : A Potential Another Option

Create your own org.eclipse.core.runtime.jobs.Job and then join() at the end:

 public static class RefCountJob extends Job { public RefCountJob() { super("REF_COUNT"); } int count = 0; public void increment() { count++; } public void decrement() { count--; } @Override protected IStatus run(IProgressMonitor monitor) { monitor.beginTask("WAITING", IProgressMonitor.UNKNOWN); while (count > 0) { Thread.sleep(200); monitor.worked(1); } monitor.done(); return Status.OK_STATUS; } } 

To use it, increment () it every time you are going to fire events, and decrease them when they are done (you have to make sure that they decrease it no matter which exception is thrown :-)

 RefCountJob ref = new RefCountJob(); // ... do stuff, everybody increments and decrements ref ref.increment(); // ... do more stuff ref.increment(); // at the end of your long-running job ref.schedule(); ref.join(); 

Answer 2

Thanks, I ended up with the following. I think this is a pretty clean solution. By the way, I would raise your answer if I had a reputation for this :)

 public class SWTThreadingUtils { public static void waitForAsyncExecsToFinish(Display display) { Object waitObj = new Object(); display.asyncExec(new DummyRunnable(waitObj)); synchronized (waitObj) { try { waitObj.wait(); } catch (InterruptedException e) { throw new RuntimeException(e); } } } private static class DummyRunnable implements Runnable { private Object waitObj; public DummyRunnable(Object waitObj) { this.waitObj = waitObj; } @Override public void run() { synchronized (waitObj) { waitObj.notify(); } } } }