How to wait for user input on JavaFX application thread without using showAndWait?

Question

I\'d like to pause the execution of a method on the JavaFX application thread and wait until the user does interaction with the UI. It\'s important not to freeze the UI.

Answer 1

I am currently running JFX 8 where I have the similar feature in the Toolkit class.

Toolkit.getToolkit().enterNestedEventLoop(obj);

and

Toolkit.getToolkit().exitNestedEventLoop(obj);

Have not looked at the JFX 9 source, but my bet is that the Platform methods are simply shortcuts to the same.

Answer 2

You can do so by using Platform.enterNestedEventLoop to pause the execution of the event handler and Platform.exitNestedEventLoop (available since JavaFX 9) to resume the execution:

private final Object PAUSE_KEY = new Object();

private void pause() {
    Platform.enterNestedEventLoop(PAUSE_KEY);
}

private void resume() {
    Platform.exitNestedEventLoop(PAUSE_KEY, null);
}

Platform.enterNestedEventLoop returns when Platform.exitNestedEventLoop is called with the same parameter passed as first argument.