Question

I’m new to Java programming and am facing a (most likely) easy problem that I don’t seem to be able to get across nor understand.

I have three different java files, one where I create an interface (SimulatorGui.java), other where I am creating a panel to use on the jTabbedPanel created in the interface (CollisionPanel.java – CollisionPanel class) and a third one, where I run a code that will create the output needed (Collision.java – Colision class).

In the Collision.java main method, I am doing the following:

  public static void main (String[] args) {

    //<editor-fold defaultstate="collapsed" desc="Simulation start procedures">
    Tally statC = new Tally ("Statistics on collisions");
    Collision col = new Collision (100, 50);
    col.simulateRuns (100, new MRG32k3a(), statC);
    //</editor-fold>


    new SimulatorGUI().setVisible(true);
    CollisionPanel update = new CollisionPanel();
    update.updatepanel();

The first block, will create the desired output. I then want to send that output to the updatepanel! I am not passing any arguments to the method as I am still trying to debug this. updatepanel method is created in the file CollisionPanel as following:

public void updatepanel(){
    System.out.println ("debug");
    jTextArea1.setText("update\n");
}

What happens then is that when I run the Collision.java file it will output the “debug” text but won’t set the text to the jTextArea1 (append doesn’t work aswell). I then created a button to try and do so and in that case it works. In CollisionPanel.java:

private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {
    // TODO add your handling code here:
    updatepanel();
}

This does the trick! I’ve searched and tried different things but can’t seem to understand why this won’t work.

Thanks in advance for your help, hope I’ve made the problem clear!

Answer 1

Okay I think I’ve eventually got the problem, and it is because of the IDE, you see in your main method you initiate a new CollisionPanel, which is wrong, netbeans has already added and initiated that panel in the SimulatorGUI, so now what you need to do is add a get method in the SimulatorGUI to get the initiated panel, then call the update method on that panel.

So add this to SimulatorGUI:

public CollisionPanel getCollisionPanel1() {
    return collisionPanel1;
}

replace your old updatePanel() method with:

 void updatepanel(String str) {
            System.out.println ("debug");
            jTextArea1.setText(str);
         //   jTextArea1.revalidate();
            jLabel1.setText("test");
        }

after that change your main too look like this:

            SimulatorGUI simulatorGUI = new SimulatorGUI();
            simulatorGUI.setVisible(true);
            CollisionPanel cp=simulatorGUI.getCollisionPanel1();
            cp.updatepanel("Hi");

and dont forget to remove the old updatePanel() method call from your CollisionPanel constructor, because now you can simply call cp.updatePanel("text here"); in your SimulatorGUI class instead of calling it only in the constructor.

I hope this is easy to grasp, if you’re unsure let me know