setting background image in applet

[Alex Kravets]

Hello,
How do I set background image for an applet, where I use GridBagLayout to position my components? Can I set a background for a JPanel, and then in turn add components to that JPanel using GridBagLayout?
thanks,
Alex

[Nathan Pruett]

Yes... but you'll have to make a special JPanel that will paint the image in the background... and make sure that any JPanels you add to it have setOpaque( false ) set on them so the Image shows through... and make sure to use the Java 2 Plugin to use Swing in your applets!

Here's some code to illustrate an implementation of the JPanel with the background image...

import java.awt.*;
import java.awt.image.*;
import javax.swing.*;
 
public class ImagePanel extends JPanel {
 
    protected Image theImage;
 
    public ImagePanel() {
        this( null );
    }
 
    public ImagePanel( Image i ) {
        super();
        setImage( i );
    }
 
    public void setImage( Image i ) {
        MediaTracker tracker = new MediaTracker( this );
        tracker.addImage( i, 0 );
        try
        {
            tracker.waitForAll();
        }
        catch( InterruptedException exception )
        {
            System.err.println( "Error - MediaTracker cannot load image." );
        }
        theImage = i;
        validate();
    }
 
    public Image getImage()
    {
        return( theImage );
    }
 
    public Dimension getPreferredSize() {
        Dimension superSize = super.getSize();
        Dimension imageSize = new Dimension( theImage.getWidth( this ),
                                             theImage.getHeight( this ) );
        Dimension returnedSize = new Dimension();
        if( superSize.getWidth() > imageSize.getWidth() ) {
            returnedSize.setSize( superSize );
        }
        else {
            returnedSize.setSize( imageSize );
        }
 
        if( superSize.getHeight() > imageSize.getHeight() ) {
            returnedSize.setSize( returnedSize.getWidth(), superSize.getHeight() );
        }
        else {
            returnedSize.setSize( returnedSize.getWidth(), imageSize.getHeight() );
        }
        return( returnedSize );
    }
 
    public void paintComponent( Graphics g ) {
        Color oldColor = g.getColor();
        g.setColor( getBackground() );
        g.fillRect( 0, 0, getWidth(), getHeight() );
        g.setColor( oldColor );
 
        if( theImage != null ) {
            int imageX = ( getWidth() + theImage.getWidth( this ) ) / 2;
            int imageY = ( getHeight() + theImage.getHeight( this ) ) / 2;
            g.drawImage( theImage, 0, 0, this );
        }
    }
 
    public static void main( String[] arg ) {
        JFrame f = new JFrame( "Test ImagePanel" );
        Image i = Toolkit.getDefaultToolkit().getImage( "washucel2.jpg" );
        ImagePanel ip = new ImagePanel( i );
        f.getContentPane().add( ip );
        ip.setLayout( new BorderLayout() );
        JPanel p = new JPanel();
        p.add( new JButton( "Press" ) );
        p.add( new JTextField( 12 ) );
        p.setOpaque( false );
        ip.add( p, BorderLayout.SOUTH );
        f.pack();
        f.setDefaultCloseOperation( f.EXIT_ON_CLOSE );
        f.setVisible( true );
    }
}

-Nate