How to stop repeated keyPressed() / keyReleased() events in Swing

Question

So the problem that I am having appears to be a bug that occurs only on Linux. I'm trying to have my swing app record when a key is pressed down, then to detect when that key is released. Now that shouldn't be in issue because KeyListener is supposed to handle this for me.

The problem is that when I hold the key down I get lots of repeated keyPressed()/keyReleased() events instead of just the single keypressed(). Does anyone have a solution or workaround for knowing when a key is really released on linux?

Thank you.

Answer 1

Users expect their keys to repeat when they hold them down for a while. In Java, that means at the very least that a lot of KeyTyped events are generated. Whether you get a bunch of pressed/released events is, I guess, implementation dependent. Java doesn't operate close enough to the operating system to tell the difference.

You could try turning off keyboard repetition in your system configuration, or setting it to very slow. I can't think of anything else to do.

Answer 2

So the problem that I am having appears to be a bug that occurs only on Linux

Yes this is a Linux problem.

On Windows when a key is held down you get multiple KeyPressed events but only a single KeyReleased event.

This question is asked often and I've never seen a good solution.

But I think the basis of a solution is to use a Timer. When the key is pressed you start a Timer. When you get another keyPressed you restart the Timer. So as long as the Timer interval is greater than the repeat rate of the key board the Timer will be continually reset when a key is held down. When keyPresses stop being generated the Timer will fire so you assume the key has been released. This implies you will have a delay in processing the keyReleased.

Answer 3

Here's the bug from Sun (includes sample work-arounds): http://bugs.sun.com/view%5Fbug.do?bug%5Fid=4153069

Answer 4

This question is duplicated here.

Here's a hack implemented as an AWTEventListener that can be installed at the start of the application.