Trouble Figuring Out How To Set Background Image

Question

Possible Duplicate:
How to set an image as a background for Frame in Swing GUI of java?

I'm having trouble figuring out how to set a background image on my window. I'm not sure whats wrong with my code. The image is called Background.jpg
Does anyone know what I'm doing wrong with my code and how it can be fixed

//apples code  

import javax.swing.JFrame;
import java.applet.*;
import javax.swing.*;
import java.awt.*;
import java.awt.Graphics;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.imageio.ImageIO;
import javax.swing.JPanel;
import java.awt.*;
import javax.swing.*;

class  Apples{

public static void main(String[] args) {
  gui go = new gui();
  go.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
  go.setSize(200,290);
  go.setVisible(true);



 }
}



 //Gui Code

    import java.awt.FlowLayout;
import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;
import javax.swing.*;
import java.awt.Color;
import java.awt.Font;
import javax.swing.JFrame;
import javax.swing.JTextArea;

public class gui extends JFrame{
     private JButton A;
     private JButton B;
     private JButton C;
     private JButton D;
     private JButton E;
     private JButton F;
     private JButton G;
     private JButton H;
     private JButton I;
     private JButton J;
     private JButton K;
     private JButton L;
     private JButton M;
     private JButton N;
     private JButton O;
     private JButton P;
     private JButton Q;
     private JButton R;
     private JButton S;
     private JButton T;
     private JButton U;
     private JButton V;
     private JButton W;
     private JButton X;
     private JButton Y;
     private JButton Z;

     public gui(){
        super("APUSH ABCs");
        setLayout(new FlowLayout());

        A = new JButton("A");
        add(A);
        B = new JButton("B");
        add(B);
        C = new JButton("C");
        add(C);
        D = new JButton("D");
        add(D);
        E = new JButton("E");
        add(E);
        F = new JButton("F");
        add(F);
        G = new JButton("G");
        add(G);
        H = new JButton("H");
        add(H);
        I = new JButton("I");
        add(I);
        J = new JButton("J");
        add(J);
        K = new JButton("K");
        add(K);
        L = new JButton("L");
        add(L);
        M = new JButton("M");
        add(M);
        N = new JButton("N");
        add(N);
        O = new JButton("O");
        add(O);
        P = new JButton("P");
        add(P);
        Q = new JButton("Q");
        add(Q);
        R = new JButton("R");
        add(R);
        S = new JButton("S");
        add(S);
        T = new JButton("T");
        add(T);
        U = new JButton("U");
        add(U);
        V = new JButton("V");
        add(V);
        W = new JButton("W");
        add(W);
        X = new JButton("X");
        add(X);
        Y = new JButton("Y");
        add(Y);
        Z = new JButton("Z");
        add(Z);

        HandlerClass handler = new HandlerClass();
        A.addActionListener(handler);
        B.addActionListener(handler);
        C.addActionListener(handler);
        D.addActionListener(handler);
        E.addActionListener(handler);
        F.addActionListener(handler);
        G.addActionListener(handler);
        H.addActionListener(handler);
        I.addActionListener(handler);
        J.addActionListener(handler);
        K.addActionListener(handler);
        L.addActionListener(handler);
        M.addActionListener(handler);
        N.addActionListener(handler);
        O.addActionListener(handler);
        P.addActionListener(handler);
        Q.addActionListener(handler);
        R.addActionListener(handler);
        S.addActionListener(handler);
        T.addActionListener(handler);
        U.addActionListener(handler);
        V.addActionListener(handler);
        W.addActionListener(handler);
        X.addActionListener(handler);
        Y.addActionListener(handler);
        Z.addActionListener(handler);
    }
      private class HandlerClass implements ActionListener{
  public void actionPerformed(ActionEvent event){

     Object button = event.getSource();

     if(button == A){
String text = "asaasas ";
  JTextArea textArea = new JTextArea(text);

  textArea.setColumns(30);
  textArea.setLineWrap( true );
  textArea.setWrapStyleWord( true );
  textArea.setSize(textArea.getPreferredSize().width, 1);
Font font = new Font("Verdana", Font.BOLD, 12);
textArea.setFont(font);
textArea.setForeground(Color.BLUE);
  JOptionPane.showMessageDialog(
   null, textArea, "Appomattox Court House", JOptionPane.PLAIN_MESSAGE);

     }else if(button == B){
     String text = "Duriing the last days of the Civil War, Robert E. Lee had abandoned the Confederate capital of Richmond and city of Petersburg, hoping to escape with the remnants of his Army of Northern Virginia to meet up with additional Confederate forces in North Carolina and resume fighting. Union Forces cut him off and finally the Continental army had to surrender. The Appomattox Courthouse is the locaiton where General Robert E. Lee of the Confederate Army surrendered his approximately 28,000 troops to Ulysses S. Grant and the Union Army on April 9, 1865, ending the American Civil War. ";
  JTextArea textArea = new JTextArea(text);

  textArea.setColumns(30);
  textArea.setLineWrap( true );
  textArea.setWrapStyleWord( true );
  textArea.setSize(textArea.getPreferredSize().width, 1);
Font font = new Font("Verdana", Font.BOLD, 12);
textArea.setFont(font);
textArea.setForeground(Color.BLUE);
  JOptionPane.showMessageDialog(
   null, textArea, "Appomattox Court House", JOptionPane.PLAIN_MESSAGE);
     } else if(button == C){

String text = "Duriing the last days of the Civil War, Robert E. Lee had abandoned the Confederate capital of Richmond and city of Petersburg, hoping to escape with the remnants of his Army of Northern Virginia to meet up with additional Confederate forces in North Carolina and resume fighting. Union Forces cut him off and finally the Continental army had to surrender. The Appomattox Courthouse is the locaiton where General Robert E. Lee of the Confederate Army surrendered his approximately 28,000 troops to Ulysses S. Grant and the Union Army on April 9, 1865, ending the American Civil War. ";
  JTextArea textArea = new JTextArea(text);

  textArea.setColumns(30);
  textArea.setLineWrap( true );
  textArea.setWrapStyleWord( true );
  textArea.setSize(textArea.getPreferredSize().width, 1);
Font font = new Font("Verdana", Font.BOLD, 12);
textArea.setFont(font);
textArea.setForeground(Color.BLUE);
  JOptionPane.showMessageDialog(
   null, textArea, "Appomattox Court House", JOptionPane.PLAIN_MESSAGE);     
       }

      }
}

Answer 1

This...

public void paint(Graphics g)
{
    // Draws the img to the BackgroundPanel.
    g.drawImage(img, 0, 0, null);
}

Is never a good idea. You've failed to honor the paint chain. The paint chain is a complex set of methods that does a lot of important work.

A better idea would be to use paintComponent

protected void paintComponent(Graphics g)
{
    super.paintComponent(g);
    // Draws the img to the BackgroundPanel.
    g.drawImage(img, 0, 0, null);
}

Another issue you will have is that your not giving the component a chance to monitor the state of the image. Because you are using Toolkit.getDefaultToolkit().createImage("Background.jpg") it is possible method will use a background thread to the load the image. You need some way to tell the component that the image has completed loading and is ready for painting...

g.drawImage(img, 0, 0, this);

This will let the component monitor the state of the image and update itself as required.

Toolkit#createImage is probably not the best choice for loading images. The method will not throw an exception if it is not able to load the image.

Better to use ImageIO#read. This will not only throw an exception if the class is unable to load the image, it's guaranteed to return a fully qualified image (that is, it will block until the image is actually loaded).

You've not enlightened us to the location of Background.jpg. If the image is a embedded resource or not. If the image is just a file (within the execution context of the application), then you attempt to the load the file is fine, if it's a embedded resource (contained within the application Jar), then you need to use Class#getResource instead...

img = ImageIO.read(getClass().getResource("/Background.jpg"));

You've not specified a preferred size for the BackgroundPanel. Some layout managers will not be able to layout this container the way you expected it to be laid out.

public Dimension getPreferredSize() {
    return img == null ? super.getPreferredSize() : new Dimension(img.getWidth(this), img.getHeight(this));
}

Also, as has already begin mentioned, don't forget to add the panel to your UI ;)

Updated with example

I also noticed that you seem to be mixing Swing and AWT components, this is never a good idea, and if you can avoid it, do so (Panel is a AWT/heavy weight component).

public class Apples {

    public static void main(String[] args) {
        new Apples();
    }

    public Apples() {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                try {
                    UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
                } catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
                }

                JFrame frame = new JFrame();
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.setLayout(new BorderLayout());
                frame.add(new BackgroundPanel());
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }
        });
    }

    public class BackgroundPanel extends JPanel {

        Image img;

        public BackgroundPanel() {
            try {
                img = ImageIO.read(getClass().getResource("/Background.jpg"));
            } catch (IOException ex) {
                ex.printStackTrace();
            }
        }

        @Override
        protected void paintComponent(Graphics g) {
            super.paintComponent(g);
            // Draws the img to the BackgroundPanel.
            if (img != null) {
                g.drawImage(img, 0, 0, null);
            }
        }

        public Dimension getPreferredSize() {
            return img == null ? super.getPreferredSize() : new Dimension(img.getWidth(this), img.getHeight(this));
        }
    }
}