avoiding flickering

[basha khan]

hi ranchers,

how can i put an image on background in a JPanel without overriding its paint() method?.i am having some dragging components over it.
i had overrided paint() method of JPanel to put background image,but inconsistent flickering occurs.how can i resolve the problom?.

anybody plz..
basha

[Nathan Pruett]

Could you post the code for the JPanel you are having the problems with?

Though, one of my first suggestions would be to override paintComponent() rather than paint()...

[basha khan]

hi nate nice to see u.
i need a background image in JFrame.i need some labels dragging on that image(above the image).
i had painted an image in JFrame
i had added jLabels on ContentPane of that frame
how can i paint my image on contentpane?.i think that 'll solve the problom.
here is a sample code..
save 2 gif images on current directory and rename as 'backgroundimage.gif' and 'labelimage.gif'. then run the code

import javax.swing.*;
import java.awt.*;
public class Sample1 extends javax.swing.JFrame
{
public Sample1()
{
initComponents ();
draw();
setSize(400,300);
}
private void initComponents()
{//GEN-BEGIN:initComponents
addWindowListener(new java.awt.event.WindowAdapter()
{
public void windowClosing(java.awt.event.WindowEvent evt)
{
exitForm(evt);
}
}
);
}//GEN-END:initComponents
/** Exit the Application */
private void exitForm(java.awt.event.WindowEvent evt)
{//GEN-FIRST:event_exitForm
System.exit (0);
}//GEN-LAST:event_exitForm
public void draw()
{
for(int i=0;i<10;i++)
{
alabel=new ALabel();
this.getContentPane().add(alabel,0);
alabel.setBounds(20,20+(i<<2),140,200);
alabel.setVisible(true);
}
this.alabel.addMouseListener(new java.awt.event.MouseAdapter()
{
public void mousePressed(java.awt.event.MouseEvent me)
{
}
public void mouseReleased(java.awt.event.MouseEvent me)
{
((javax.swing.JLabel)me.getSource()).setBounds(me.getX(),me.getY(),140,200);
}
});
this.alabel.addMouseMotionListener(new java.awt.event.MouseMotionAdapter()
{
public void mouseDragged(java.awt.event.MouseEvent me)
{
Component c = (Component)me.getSource();
Point p = me.getPoint();
p = SwingUtilities.convertPoint( c, p, Sample1.this );
c.setLocation( p );
c.setBounds((int)p.getX(),(int)p.getY(),140,200);
c.setVisible(true);
}
});
}
public void paint(java.awt.Graphics g)
{
g.drawImage((new javax.swing.ImageIcon("backgroundimage.gif")).getImage(),10,10,this);
//g.drawImage(Toolkit.getDefaultToolkit().createImage("backgroundimage.gif"),10,10,this);
//not getting the image
}
/**
* @param args the command line arguments
*/
public static void main (String args[])
{
new Sample1 ().show ();
}
// Variables declaration - do not modify//GEN-BEGIN:variables
private javax.swing.JLabel alabel;
// End of variables declaration//GEN-END:variables
}
// label
class ALabel extends javax.swing.JLabel {
public ALabel()
{
this.setIcon(new javax.swing.ImageIcon("labelimage.gif"));
}
}

i need bacground images on Desktoppane also.how can i achieve that using aggregation instead of subclassing and overriding Paint() of jDesktopPane?.
lovingly
basha

[Nathan Pruett]

Hmmm... there were lots of problems with the code... I *think* the problem that was causing the flickering was the overridden paint method for the JFrame, you should probably make it a JPanel and override the JPanel's paintComponent() method. Also, you were re-loading the background image every time it needed to repaint. This was also probably adding to the flicker problem. Here's a fixed version that I think does what you want it to:

import javax.swing.*;
import java.awt.*;
import java.awt.event.MouseEvent;
import java.awt.event.MouseMotionListener;
 
// Changed main class to a JPanel instead of a JFrame.
public class Sample2 extends JPanel {
    
    // This needed to be an *array* of JLabels, not just
    // one JLabel.
    private JLabel[] alabel;
    
    // Saving the background image, so it does not need to
    // be re-loaded every time it is re-drawn.
    private Image backgroundImage;
    
    public Sample2() {
        
        // Since we are controlling where the labels are
        // going to go, we don't want a layout manager. 
        // However, this means that we have to use setBounds()
        // for *everything*.
        setLayout( null );
        
        // Loading the background image.  The MediaTracker
        // part makes sure the image is completely loaded 
        // before it is painted... otherwise the image takes
        // a while to show up on the background.
        Image image = Toolkit.getDefaultToolkit().createImage( "backgroundimage.gif" );
        MediaTracker mt = new MediaTracker( this );
        mt.addImage( image, 0 );
        try {
            mt.waitForID( 0 );
        }
        catch ( InterruptedException x ) {
            x.printStackTrace();
        }
        backgroundImage = image;
        
        // Set up the icon and mouse listener we want for 
        // the labels, then create all the labels.
        ImageIcon icon = new ImageIcon( "labelimage.gif" );
        MouseMotionListener mover = new MouseMotionListener() {
            public void mouseDragged( MouseEvent me ) {
                Component c = (Component)me.getSource();
                Point p = me.getPoint();
                p = SwingUtilities.convertPoint( c, p, getParent() );
                c.setLocation( p );
            }
            
            public void mouseMoved( MouseEvent me ) {}
        };
        alabel = new JLabel[10];
        for( int i=0; i < alabel.length; i++ ) {
            alabel[i] = new JLabel( icon );
            alabel[i].setBounds( 20, 20 + (i<<2), icon.getIconWidth(), icon.getIconHeight());
            add( alabel[i] );
            alabel[i].addMouseMotionListener( mover );
        }
    }
    
    // Paint the JPanel.
    public void paintComponent( Graphics g ) {
        // You need to call super.paintComponent() or things
        // aren't drawn correctly...
        super.paintComponent( g );
        
        // Draw the background image.
        g.drawImage( backgroundImage, 10, 10, this );
    }
    
    // Changed main to create a JFrame and add the Sample2
    // JPanel to it.  Removed all the window listener code,
    // since it could just be replaced by setting the 
    // default close operation.
    public static void main (String args[]) {
        JFrame f = new JFrame( "Sample2 Test" );
        f.getContentPane().add( new Sample2() );
        f.setDefaultCloseOperation( WindowConstants.EXIT_ON_CLOSE );
        f.setSize( 300, 300 );
        f.show();
    }
}

Here is another post that I gave code for how to add a background image to a JDesktopPane...

[basha khan]

thanks nate..
u r really helpfull to me.i love people like u who really having some value on most dimensions...
take care ...
basha