use image for background

[tony_stark]

Hello first time in this forum.

I have this project and one the tasks is to use the Programs>Set background... menuItem to set an image as the background of the main window. The problem is that when i click a menu from the menubar or i minimize the main window the image dissapeares (partialiy when i click a menu and entirely when i minimize). What kind of updating i need to keep the image for background?

Please help !

MainWindow.java

import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.KeyEvent;
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.JFileChooser;
import javax.swing.JFrame;
import javax.swing.JMenu;
import javax.swing.JMenuBar;
import javax.swing.JMenuItem;
import javax.swing.JPanel;
import javax.swing.WindowConstants;

public class MainWindow extends JFrame implements ActionListener{
    
    public static final int S = 500;
    
    public MainWindow () {
    
        setSize(S,S);
        setTitle("Whatever");
        setResizable(false);
                                                
        setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
        
        JMenu programMenu = new JMenu("Program");
        programMenu.setMnemonic(KeyEvent.VK_P);
                
        JMenuItem setBack = new JMenuItem("Set background...");
        setBack.setMnemonic(KeyEvent.VK_B);
        setBack.addActionListener(this);
        
        programMenu.add(setBack);
        
        JMenuBar mbar = new JMenuBar();
        mbar.add(programMenu);

        
        setJMenuBar(mbar);
        
    }

    @Override
    public void actionPerformed(ActionEvent e) {

        String actionCommand = e.getActionCommand();
        
        if (actionCommand.equals("Set background...")) {
        
            JFileChooser fc = new JFileChooser();
            fc.addChoosableFileFilter(new ImageFilter());
            int returnVal = fc.showOpenDialog(this);
            
            if (returnVal == JFileChooser.APPROVE_OPTION) {
                
                File file = fc.getSelectedFile();
                
                try {
                    
                     img = ImageIO.read(file);
                     getContentPane().getGraphics().drawImage(img,0,0,null);
                    
                } catch (IOException ex) {
                    Logger.getLogger(MainWindow.class.getName()).log(Level.SEVERE, null, ex);
                }                

            }
        
        }
       
    }
    
}

MainClass.java

public class MainClass {

    public static void main(String[] args) {
        
        MainWindow mainWindow = new MainWindow();
        mainWindow.setVisible(true);

    }
}

[camickr]

Never use getGraphics to do any custom painting.

To display an image use an Icon on a JLabel or do custom painting on a JPanel. See Background Panel « Java Tips Weblog for and example of both approaches.