Question

I have 2 classes .java

The main :

public class Controller extends javax.swing.JFrame
{   
    public static void updateProgressBar(int i) {
        jProgressBar1.setValue(i);
        jProgressBar1.repaint();
    }

    public static void main(String args[]) {

        /* Create and display the form */
        java.awt.EventQueue.invokeLater(new Runnable() {
            public void run() {
                Controller app = new Controller();
                app.setVisible(true);
                app.setResizable(false);
            }
        });
    }

    private void jButton2ActionPerformed(java.awt.event.ActionEvent evt) {
        ChildModel model = new ChildModel();
        Thread t1 = new Thread(model);
        t1.start();
    }

    private javax.swing.JProgressBar jProgressBar1; //Initialized with Netbeans builder
}

My ChildModel (ChildModel.java) computes some code (that takes around 10-20 sec) and I want to show the progress on the father class (Controller.java).

Here is my ChildModel :

public class ChildModel implements Runnable
{
    public ChildModel(){ /* Something */ }

    public void complexMath()
    {
        //Lots of logic here
        Controller.updateProgression(purcent);
    }

    @Override
    public void run() {
        complexMath();
    }
}

The problem is obviously my static void updateProgressBar that cannot modify a non-static variable. How can I accomplish this ?

Answer 1

The jProgressBar1 variable is an instance variable, so you can’t access it from a static method. And the method shouldn’t be static: you want to update the progress in the controller, and not in all the Controller instances.

Pass a reference to the controller to the ChildModel, and use this reference from the ChildModel in order to update the progress bar. Also remember that all Swing interactions must be done in the EDT, and not in a background thread. SO the code should look like this:

public class Controller extends javax.swing.JFrame
{   
    public void updateProgressBar(int i) {
        jProgressBar1.setValue(i);
        // no need for repaint. The progress bar knows it must be repainted 
        // when its value changes
    }

    public static void main(String args[]) {

        /* Create and display the form */
        java.awt.EventQueue.invokeLater(new Runnable() {
            public void run() {
                Controller app = new Controller();
                app.setVisible(true);
                app.setResizable(false);
            }
        });
    }

    private void jButton2ActionPerformed(java.awt.event.ActionEvent evt) {
        ChildModel model = new ChildModel(this);
        Thread t1 = new Thread(model);
        t1.start();
    }

    private javax.swing.JProgressBar jProgressBar1; //Initialized with Netbeans builder
}

public class ChildModel implements Runnable
{

    private Controller controller;

    public ChildModel(Controller controller){
        this.controller = controller;
    }

    public void complexMath()
    {
        //Lots of logic here
        SwingUtilities.invokeLater(new Runnable() {
            @Override
            public void run() {
                controller.updateProgression(percent);
            }
        });
    }

    @Override
    public void run() {
        complexMath();
    }
}