Question

Everytime I make code involving a while loop, the GUI freezes up, creating an infinite loop. I want to know how I can prevent this. Here is an example, where I try to make the loop conditional on the state of Jtogglebutton, which freezes up, making the loop infinite:

boolean state = StartStop.getModel().isSelected(); //whether toggle button is on or off
int speed = SpeedSelection.getValue(); //value of the speed selection bar
ScrollPane.getHorizontalScrollBar().getModel().setValue(position);

while(state == true){

        try {
            Status.setText("Running...");
            StartStop.setText("Stop");
            position += speed;
            System.out.println(position);
            ScrollPane.getHorizontalScrollBar().getModel().setValue(position);

            Thread.sleep(250);
            state = StartStop.getModel().isSelected();
            speed = SpeedSelection.getValue();
            //start scrolling the scroll pane
        }

        catch (InterruptedException ex) {
            Logger.getLogger(GUI.class.getName()).log(Level.SEVERE, null, ex);
        }
}

if(state == false){

    Status.setText("Paused.");
    StartStop.setText("Start");
    //stop scrolling
}

Answer 1

UI events, repainting, etc is handled by a single thread. You’re causing that thread to get stuck in a loop; nothing else can happen (events from the UI) while it’s looping. You need to do whatever it is you’re trying to do in a separate thread.