IDE hangs in debug mode on break point in java fx application

Question

I have a problem while debugging in IntelliJ IDEA, it hangs in debug mode on break point in listeners in javafx application. I tried to increase heap space, but it's not help. Maybe someone had such problem too, please, suggest me what to do.

Answer 1

Set this as a VM parameter:

-Dsun.awt.disablegrab=true 

It will mess up drag-and-drop, and leave an artifact on your screen while the debugger is paused - but it will let you debug. It happens whenever you block the JavaFX thread.

Answer 2

This can happen for a simple reason: The application has a lock on the desktop, for example a modal dialog or a popup or an open menu. Then it stops in a breakpoint. This notifies the IDE. Now the IDE tries to do something on your desktop but can't since the application still has a lock on the whole desktop -> deadlock.

You can use a tool like Chronon which records the whole program and lets you move back and forth on the timeline.

The last option is logging or poor man's debugger (System.out) instead.

[EDIT]

it's hard to check with System.out which of 20 parameters not equal.

It's actually pretty easy:

System.out.println("check"); if(!a1.equals(b2)) System.out.println(a1+"!="+b1); 

Then duplicate the last line. That way, you will only get output when something is actually interesting (and not for the 19 equal parameters). Add some patterns to the output if you can't distinguish aX from aY (i.e. both are true):

if(!a1.equals(b2)) System.out.println("a1:"+a1+"!="+b1);