JFrame (swing) switching repeating actions with buttons

Question

I want a JFrame application with 2 buttons (eventually more) that I can use to switch between multiple repeating actions, ofr simplicity I'm just using a console print for now, though it will probably be calling a method instead later. Here is the framework for the JFrame:

public class DayNight extends JFrame implements ActionListener{

    //JFrame entities
    private JPanel animationPanel;
    private JButton button;
    private JButton button2;


    public static void main(String[] args) {
        DayNight frame = new DayNight();
        frame.setSize(2000, 1300);
        frame.setLocation(1000,350);
        frame.createGUI();
        frame.setVisible(true);
        frame.setTitle("Day/Night Cycle, Rogier");
    }

   private void createGUI() {
    setDefaultCloseOperation(EXIT_ON_CLOSE);
    Container window = getContentPane();
    window.setLayout(new FlowLayout() );
    animationPanel = new JPanel();
    animationPanel.setPreferredSize(new Dimension(2000, 900));
    animationPanel.setBackground(Color.black);
    window.add(animationPanel);

    button = new JButton("choice1");
    button.setFont(new Font("Arial", Font.PLAIN, 50));
    window.add(button);
    button.setActionCommand("choice1");
    button.addActionListener(this);

    button2 = new JButton("choice2");
    button2.setFont(new Font("Arial", Font.PLAIN, 50));
    window.add(button2);
    button2.setActionCommand("choice2");
    button2.addActionListener(this);
   }
}

I've tried the following:

public void actionPerformed(ActionEvent event) {
    String command = event.getActionCommand();
    while ("Stop"!=(command)){
        command = event.getActionCommand();
        try{
            Thread.sleep(500);
            if ("choice1".equals(command)){
                System.out.println("choice1");
            }
            else if("choice2".equals(command)){
                System.out.println("choice2");
            }
            else{
                System.out.println("no choice");
            }
        }   
        catch(InterruptedException ex){
            Thread.currentThread().interrupt();
        }

    }
}

But after I click a button it keeps stuck on that print and I can't even interact with the buttons anymore. Am I missing something or do I need a completely different structure? I've examined a lot of different programs but they are too complicated for me to understand, reading the concurrency in swing also didn't clear it up for me.

Edit: There is no "stop" command yet because I don't need it for now.

Answer 1

There are many things wrong with your code.

It starts with wrong comparison of strings ( see here ).

But your actual problem: you are sleeping the event dispatcher thread ( see there )

So your idea of sleeping with an event listener is simply the wrong approach. You can't do it this way. You have to re-think your approach there.

And the real answer here is: you are lacking basic knowledge of Java. Consider learning such basic things first before further overburdening yourself if Swing UI coding.

Your requirement seems to be: after that button was hit - and a certain amount of time passed you want to print something on the console. You can do that like:

public void actionPerformed(ActionEvent event) {
   String command = event.getActionCommand();
   command = event.getActionCommand();
   Runnable printChoice = new Runnable() {
     @Override
     public void run() {
      try{
        Thread.sleep(500);
        if ("choice1".equals(command)){
            System.out.println("choice1");
        }
        else if("choice2".equals(command)){
            System.out.println("choice2");
        }
        else{
            System.out.println("no choice");
        }
      }   
      catch(InterruptedException ex){
        Thread.currentThread().interrupt();
      }
    });
    new Thread(printChoice).start();
}

The above:

• creates a Runnable that simply waits to then print something
• uses a new Thread (not the event dispatcher thread) to do that

I didn't run this through the compiler - it is meant as "pseudo code" to give you some ideas how to solve your problem.

But further thinking about this - I think this is going in the wrong direction. You don't want that anything is waiting when you develop a reasonable UI application.

In other words: you think of:

• button A is clicked - some code starts "looping"
• when the user makes another choice, that "looping" code notices that and does something

Wrong approach. Instead work along these lines:

• user clicks a button, and maybe that enables other UI components
• user does something with those other UI components - triggering other actions

Example: changing radiobuttons causes events to be fired. You should not have a loop that regularly keeps checking those buttons. Instead you define a clear flow of actions/events the user has to follow in order to trigger a certain action.