GUI added components but when displayed shows blank

Question

For some reason, when I run the code in the main it works but currently I have the code only run when a JButton is

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import java.awt.Color;
import java.util.Random;

import javax.swing.JFrame;
import javax.swing.JProgressBar;


public class JavaCompilingJOP {

    private JFrame framed = new JFrame();
    private JProgressBar bar = new JProgressBar(0,100); //0 through 100 is the compiling until reaches that number
    private Color startProgress = Color.RED;
    private int loadingPercent = 0;

    public JavaCompilingJOP(){
        framed.setLayout(null);
        framed.setSize(500, 200);
        framed.setTitle("Compiling JOptionPane...");
        framed.setLocationRelativeTo(null);
        //Ok now lets make the GUI happen boys!
        framed.getContentPane().setBackground(Color.BLACK); //Because startProgress is ze theme of ze game!

        bar.setForeground(startProgress);
        bar.setStringPainted(true);
        bar.setValue(loadingPercent);
        bar.setString(loadingPercent + "%");
        bar.setBounds(50, 50, 400, 100);
        framed.add(bar);

        System.out.println("Make visible an run!");

        framed.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
        framed.setResizable(false);

        framed.setVisible(true);

        doTimer();
    }

    private void doTimer(){
        Random obj = new Random();
        for(int i = 0; i < 100; i++){
            loadingPercent++;
            bar.setValue(loadingPercent); //Updates counter
            bar.setString(loadingPercent + "%"); //Updates progressbar
            startProgress = new Color(startProgress.getRed()-2,startProgress.getGreen()+2,startProgress.getBlue());
            bar.setForeground(startProgress);
            try{Thread.sleep(100 + obj.nextInt(200));}catch(Exception E){}

        }
        System.out.println("Java compiled!");
        framed.setVisible(false);
    }
}

For some reason all I am getting though when called is a white screen that seems to neglect disposing on close because when I hit to close it.. it doesn't either. Keep in mind that when I run it in the main it works but when inside the ActionListener of the button, it gives me a blank screen that still performs it's progressbar stuff. Im stuck on this.

Answer 1

Your JButton's actionPerformed() code gets executed on the Java event dispatch thread (EDT) and this is why the GUI "freezes" and you see a black screen.
Doing so, also blocks the "close" event from being executed as well as any other swing event.
Important:
The EDT is a special thread which should be handled very carefully.
Please take the time and read on EDT and how to properly use it here.

Correct method:
doTimer() should never run on Java event dispatch thread (EDT) since it simulates (I hope) some long-running task.
To make sure we handle the EDT correctly we use a SwingWorker.
SwingWorkers are special constructs designed to perform lengthy GUI-interaction tasks in a background thread.
Since this is kinda tricky to handle for the first time, I added the following code for you:

@Override
public void actionPerformed(ActionEvent e) {
    SwingWorker<Object, Object> sw = new SwingWorker<Object, Object>() {
        @Override
        protected Object doInBackground() throws Exception {
            // Code here will be executed in a background thread
            // This is where all background activities should happen.
            doTimer();
            return null;
        }
    };
    sw.execute();
    //  doTimer(); Bad Idea as this will execute on EDT!
}