java.awt.Robot.waitForIdle() is unrealiable

Question

We are seeing frequent timing issues in our nightly UI tests. The tests often fail because events performed by the java.awt.Robot have not completed before the test code tries to verifying the results.

We are code like using:

Point p = cb.getLocationOnScreen();
int m = 5;
if (cb.getWidth()<5||cb.getHeight()<5)
    m=3;
System.out.println("Click at " + (p.x+m) + "," + (p.y+m));
robot.mouseMove(p.x + m, p.y + m);
robot.mousePress(MouseEvent.BUTTON1_MASK);
robot.mouseRelease(MouseEvent.BUTTON1_MASK);
robot.waitForIdle();
Thread.sleep(100);
// Verify results...

We keep having the bump up the Thread.sleep to ensure things complete on the event thread (things like clicking on a button or typing text) despite the java.awt.Robot.waitForIdle() call.

I found this question (Does java.awt.Robot.waitForIdle() wait for events to be dispatched?) which says to use java.awt.Toolkit.realSync(), but this is not an accessible method and with Java 9 coming, I'd rather not add any unnecessary reflection to our tests.

Are there better solutions? Or do people use realSync() or just increase the wait time until tests pass reliably?

UPDATE

I tried using sun.awt.SunToolkit.realSync(), but it is hanging in some tests and never returning. It looks like the EventThread is painting borders and such.

Looks like my only solution is to bump the sleep time up until the test can actually pass reliably. Yuck.

UPDATE 2

I figured out the first hang I had with realSync(). It was a problem in our code, where some paint code called a get method that called a set method which queued up another paint. Repeat forever.

Fixed our code and realSync() worked for a while, sort of. It still seems to return before it should. No idea why and I have no work around.

Also, I've seen realSync() hang and time out on my Linux box running under Java 1.7, but it works under Java 1.8. Very reliable tool here. /s

So, back the to original question. What is a decent way to tell when UI updates are done?

Have you tried with setting [`AutoWaitForIdle`](https://docs.oracle.com/javase/7/docs/api/java/awt/Robot.html#setAutoWaitForIdle(boolean)) to on? — TT., Jun 20 '17 at 16:41
Not sure I see the difference between AutoWaitForIdle and manually calling waitForIdle(). — Stephen M -on strike-, Jun 20 '17 at 16:42
If that doesn't work and you don't trust `Robot.waitForIdle`, you might do the "verify results" from a Runnable you schedule using `SwingUtilities.invokeLater`. The Runnable is put on the event dispatch queue and should be processed after all what is on the queue. — TT., Jun 20 '17 at 16:55
My boss is looking at the AssertJ Swing robot as a replacement for the java.awt.Robot. — Stephen M -on strike-, Jul 18 '18 at 21:51

score 0 · Answer 1 · answered Jul 10 '17 at 22:12

0

I came to the conclusion that I did need to use SunToolkit.realSync() and it seems to work correctly for Java 9 as well.

It seems, although I couldn't find any hard evidence, that realSync() waits for all graphics related threads while Robot.waitForIdle() and SwingUntilities.invokeLater() only wait for the Java EventThread to finish it's work.

If someone comes up with a better answer, I'd being will to accept that instead of my answer.

answered Jul 10 '17 at 22:12

Stephen M -on strike-

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Unaccepted my answer, because today, under Java 1.7 realSync() hangs. No idea why as I have no visibility into the code. – Stephen M -on strike- Jul 19 '17 at 20:49

java.awt.Robot.waitForIdle() is unrealiable

1 Answers1