Weird bug involving background images in java

Question

My problem is that when I run my program I get a white screen and text from an earlier build instead of the background image that's suppose to be displayed. I've deleted all the code that was associated with that build.

I've looked around for help and all the threads I've seen say to write the code how I've set it up. I don't understand where the displayed background is even coming from.

Here is the relivent code:

package tactics;

import java.awt.*;
import java.awt.image.BufferedImage;
import java.io.IOException;
import javax.swing.JFrame;

public class Tactics2 extends JFrame{
    private Screen s;
    private BufferedImage bg;
    private BufferedImage template;
    private boolean loaded = false;

    public static void main(String[] args) throws IOException{ 

        DisplayMode dm = new DisplayMode(1024, 768, 16, DisplayMode.REFRESH_RATE_UNKNOWN);
        Tactics2 t = new Tactics2();
        t.run(dm);
    }

    //run method
    public void run(DisplayMode dm) throws IOException{
        loadpics();

        s = new Screen(); 
        try{
            s.setFullScreen(dm, this);
            try{
                Thread.sleep(5000);
            }catch(InterruptedException ex){}
        }finally{
            s.restoreScreen();
        }
    }

    public void loadpics() throws IOException{
        bg = new BufferedImage(1024, 768, BufferedImage.TYPE_INT_RGB);
        template = new BufferedImage(1024, 768, BufferedImage.TYPE_INT_RGB);
        ChaosBack cb = new ChaosBack();
        bg = cb.ChaosBack(bg, template);
        loaded = true;
        repaint();
    }

    @Override
    public void paint(Graphics g){
        if(loaded){
            g.drawImage(bg, 0, 0, null);
        }
    }
}

Answer 1

You've broken the paint chain

@Override
public void paint(Graphics g){
    if(loaded){
        g.drawImage(bg, 0, 0, null);
    }
}

Basically, you've failed to call super.paint. Graphics is a shared resource, that is, everything painted for a given paint cycle uses the same Graphics context.

Part of the job of the paint chain is to prepare it for painting by clearing the Graphics context.

You should avoid overriding paint of a top level container for a number reasons. It's not double buffered, so it may flicker as it's updated and it doesn't take into consideration the frame decorations, meaning you can end up painting underneath the borders of the frame, instead within the viewable area.

You'd better of creating a custom component, extending from something like JPanel and overriding it's paintComponent method (making sure you call super.paintComponent)

Thread.sleep(5000); is a REALLY bad idea within a Swing application. It's possible to actually stop your application cold and stop it from been updated/painted or respond to any user interaction.

Swing is not thread safe. This means that all changes to the UI must be made from within the context of the Event Dispatching Thread.

Take a look at:

• Performing Custom Painting
• Painting in AWT and Swing
• Concurrency in Swing
• Initial Threads
• How to Use Swing Timers

For details and ideas