Repaint JInternalFrame transparent over a picture

Question

Hi,
I have a problem using a non-opaque JInternalFrame, with a content pane which has a background with ALPHA.
When I move the frame over a picture, it does not repaint() automatically.
But, when I use a ComponentListener to repaint() it manually (in componentMoved() method), there are flikerings...
I noticed that, when resizing the frame, the "automatic" repaint is good (really good).
Does anybody know how to "use" the same way to repaint() the frame when I move it ?
Here is an example :
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
public class EssaiRepaint {
public static void main(String[] aArgs) {
JFrame oFrame = new JFrame("Repaint Test"); oFrame.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
Container oContent = oFrame.getContentPane();
oContent.setLayout(new BoxLayout(oContent, BoxLayout.Y_AXIS));
JDesktopPane oDesktop = new JDesktopPane();
oContent.add(oDesktop);
ImageIcon oIcon = new ImageIcon("aRatherBigPic.jpg");
JLabel oLabel = new JLabel(oIcon);
oLabel.setSize(350,250);
oDesktop.add(oLabel, JLayeredPane.DEFAULT_LAYER, 0);
final JInternalFrame oIFrame = new JInternalFrame("Test", true, true , true, true);
// Try both by uncommenting the following lines
/*oIFrame.addComponentListener(new ComponentAdapter() {
public void componentMoved(ComponentEvent aEvent) {
oIFrame.repaint();
oIFrame.setOpaque(false);
Color oBg = oIFrame.getContentPane().getBackground();
oIFrame.getContentPane().setBackground(new Color(oBg.getRed(), oBg.getGreen(), oBg.getBlue(), 128));
oIFrame.setSize(200,200);
oIFrame.setVisible(true);
oDesktop.add(oIFrame, JLayeredPane.DEFAULT_LAYER, 0);
oFrame.setSize(500,600);
oFrame.setVisible(true);
Thanks a lot,
Luc.

Answer 1

Not sure if this is what you are looking for, but I think the flickering is caused because multiple componentMoved events are generated and Swing can't repaint fast enough. I don't know how to speed up the painting so I deferred the repaint until the component is finished moving:
final Timer timer = new Timer(50, new ActionListener()
     public void actionPerformed(ActionEvent e)
          oIFrame.repaint();
timer.setRepeats( false );
oIFrame.addComponentListener(new ComponentAdapter()
     public void componentMoved(ComponentEvent aEvent)
          if (timer.isRunning())
               timer.restart();
          else
               timer.start();
});