widget not loading in frame

[abrar alvi]

hi, i am trying out the MiniMusicPlayer3 program from the book HeadFirst Java...

Problem: My class which extends JPanel is not loading in my frame.... but the events are occurring...


This is my code:

import java.awt.Color;
import java.awt.Graphics;
import java.awt.Graphics2D;
import javax.sound.midi.*;
import javax.swing.JFrame;
import javax.swing.JPanel;


public class MiniMusicPlayer3 {

    static JFrame frame;
    static MyDrawPanel m1;

    public static void main(String[] args) {
        MiniMusicPlayer3 pro = new MiniMusicPlayer3();        
        pro.go();
        
    }

    public void setupGui() {
        m1=new MyDrawPanel();
        frame= new JFrame("my frame");
        frame.setContentPane(m1);
        frame.setBounds(30, 30, 200, 200);
        frame.setVisible(true);
       
    }

    public void go() {
        
        setupGui();
        
        try {
            Sequencer sequencer = MidiSystem.getSequencer();
            sequencer.open();
            sequencer.addControllerEventListener(m1,new int[] {127});
            Sequence seq = new Sequence(Sequence.PPQ, 4);
            Track track = seq.createTrack();
            int r = 0;
            for (int i = 0; i < 60; i += 4) {
                r=(int) ((Math.random()*50)+1);
                track.add(makeEvent(144, 1, r, 100, i));
                track.add(makeEvent(176, 1, 127, 0, i));
                track.add(makeEvent(128, 1, r, 100, i + 2));
            }
            sequencer.setSequence(seq);
            sequencer.setTempoInBPM(120);
            sequencer.start();
        } catch (Exception ex) {
            ex.printStackTrace();

        }
    }

    public MidiEvent makeEvent(int comd, int chan, int one, int two, int tick) {
        MidiEvent event = null;
        try {

            ShortMessage a = new ShortMessage();
            a.setMessage(comd, chan, one, two);
            event = new MidiEvent(a, tick);
        } catch (Exception ex) {
            ex.printStackTrace();
        }
        return event;
    }

    class MyDrawPanel extends JPanel implements ControllerEventListener {

        boolean msg = false;

        @Override
        public void controlChange(ShortMessage event) {
            System.out.println(event);
            msg = true;
            repaint();

        }

        public void paintComponenet(Graphics g) {

            if (msg) {
                Graphics2D g2 = (Graphics2D) g;
                int r = (int) (Math.random() * 250);
                int gr = (int) (Math.random() * 250);
                int b = (int) (Math.random() * 250);
                g2.setColor(new Color(r, gr, b));
                int ht = (int) ((Math.random() * 120) + 10);
                int width = (int) ((Math.random() * 120) + 10);
                int x = (int) ((Math.random() * 40) + 10);
                int y = (int) ((Math.random() * 40) + 10);
                g2.fillRect(x, y, width, ht);
                msg = false;
            }
        }
    }
}

help me...

[Campbell Ritchie]

Why have you got static fields? I think those fields should go with an object and should not be static.

Which page is it on? I have my copy here, and it would help to compare your code with what was printed.

[Jelle Klap]

In your MyDrawPanel class you attempt to override JPanel#paintComponent(), but you've misspelled the name as paintComponenet(). Your method never gets invoked, which is why you're only seeing the default empty JPanel graphics

If you use the @Override annotation on a method that should be an overrides of a super class method or an implementation of an interface method, you can prevent this kind of thing very easily. In fact you seem to have done just that with the controlChange() method...

[abrar alvi]

Campbell Ritchie wrote:Why have you got static fields? I think those fields should go with an object and should not be static.

Which page is it on? I have my copy here, and it would help to compare your code with what was printed.

The code is at page 392

[abrar alvi]

Jelle Klap wrote:In your MyDrawPanel class you attempt to override JPanel#paintComponent(), but you've misspelled the name as paintComponenet(). Your method never gets invoked, which is why you're only seeing the default empty JPanel graphics

If you use the @Override annotation on a method that should be an overrides of a super class method or an implementation of an interface method, you can prevent this kind of thing very easily. In fact you seem to have done just that with the controlChange() method...

Thanks Jelle Klap,

Really it was a silly mistake....

Yes, now the code is running just fine.....