How do I make a thread wait for JFrame to close in Java?

Question

When the program starts, a new JFrame is created. Once the user clicks the start button a thread is created and started. Part of this threads execution is to validate the data on the form and then execute with that data. Once the data has been validated the thread calls dispose() on the original frame and then creates a new JFrame that acts as a control panel.

There is also an automatic mode of the program that doesn't display any GUI at all, this mode reads data from a configuration file and then starts the execution thread and runs everything but without the control panel.

I want the program to end once the thread completes, but in GUI mode, only if the user has closed the control panel as well. Is it possible to make the thread wait for the frame to close. I assuming that the frame is run from it's own Thread? or is that not the case.

Thanks.

Answer 1

The answer you chose is a little awkward. Using Thread.sleep(1000) will check for window state every second. It is not a performance issue, but just bad coding style. And you may have a one second response time.

This code is a little bit better.

private static Object lock = new Object();
private static JFrame frame = new JFrame();
/**
 * @param args
 */
public static void main(String[] args) {

    frame.setSize(300, 300);
    frame.setDefaultCloseOperation(JFrame.HIDE_ON_CLOSE);
    frame.setVisible(true);

    Thread t = new Thread() {
        public void run() {
            synchronized(lock) {
                while (frame.isVisible())
                    try {
                        lock.wait();
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                System.out.println("Working now");
            }
        }
    };
    t.start();

    frame.addWindowListener(new WindowAdapter() {

        @Override
        public void windowClosing(WindowEvent arg0) {
            synchronized (lock) {
                frame.setVisible(false);
                lock.notify();
            }
        }

    });

    t.join();
}