How to detect whether my Java application is active?

Question

I want to pause my game (written in Java Swing), when the player switches to another application.

But I did not find a way to detect this switch. window.isActive() only works for multiple windows within one Java application. But it does return true, when a different application has the focus.

The same is true for the KeyboardFocusManager, it returns the window of my application that had the focus before the focus was given to another application.

Answer 1

Use the focus subsystem, as documented here.

An example of detecting focus being gained:

//Make textField get the focus whenever frame is activated.
frame.addWindowFocusListener(new WindowAdapter() {
    public void windowGainedFocus(WindowEvent e) {
        textField.requestFocusInWindow();
    }
});