OverlayLayout for JPanel with two JLabels

Question

I can't seem to get this to work or find information (not one of my books mentions OverlayLayout, nor is there a tutorial using one). Here's the layout (pardon the pun) of my app:
JFrame
     JMenuBar
     JToolBar
     JPanel
          JScrollPane
               JViewport
                    JPanel (view)
                         JLabel (background image)
                         JLabel (foreground drawing)
     JLabel (status bar)The JPanel (view) has an OverlayLayout so that the two JLabels can sit ontop of one another (as specified in the API docs for OverlayLayout - which is the only info to be found on the darned thing - and little at that). The JLabel (foreground drawing) is setOpaque(false) to see the image in JLabel (image). I see the image but not the drawing. The retrieved size for the JLabel (drawing) is (0,0), but if the preferredSize is set for it, it restricts everything inside the JScrollPane (JViewport, JPanel (view), and JLabel (image)) to that value and viewport changes are not broadcast.
This is turning out to be a lose, lose, lose, lose situation. No matter what I need to do, I cannot get two of anything on top of each other inside a JScrollPane. Any suggestions or working code are greatly appreciated.
Robert Templeton

Answer 1

Okay, here's how I did it. Couple points of interest: You MUST use setPreferredSize(image.width,image.height) and NOT setSize(image.width,image.height). The latter has no effect on the JPanel's size. Set the layout for the JPanel to GridLayout and add just that one JLabel. It will be stretched to fit the entire JPanel. Set JLabel to setOpaque(false) and the image is visible with the drawing on top. Yay!
In the JFrame's JPanel
          // Set up the scroll pane.
          sglass = new ScrollableGlassLabel();
          scroller = new ScrollablePicture(8);
          scroller.add(sglass);
          pictureScrollPane = new JScrollPane();
          // Create our own viewport, instead of the default one
          viewport = new IViewport(this,pictureScrollPane,scroller);
          pictureScrollPane.setViewport(viewport);
          // Setup our view in the scroll pane's viewport
          pictureScrollPane.setPreferredSize(new Dimension(256, 256));
          pictureScrollPane.setViewportBorder(BorderFactory.createLineBorder(Color.black));
          // Put it in this panel.
          setLayout(new BoxLayout(this, BoxLayout.X_AXIS));
          add(pictureScrollPane, 0);
          setBorder(BorderFactory.createEmptyBorder(20,20,20,20));ScrollablePicture:
public class ScrollablePicture extends JPanel implements Scrollable {
     private int maxUnitIncrement = 1;
     Image image = null;
     public ScrollablePicture(int m) {
          super();
          maxUnitIncrement = m;
          setOpaque(false);
          setLayout(new GridLayout());
     public Dimension getPreferredScrollableViewportSize() {
          return getPreferredSize();
     public int getScrollableUnitIncrement(Rectangle visibleRect, int orientation, int direction) {
          //Get the current position.
          int currentPosition = 0;
          if (orientation == SwingConstants.HORIZONTAL)
               currentPosition = visibleRect.x;
          else
               currentPosition = visibleRect.y;
          //Return the number of pixels between currentPosition
          //and the nearest tick mark in the indicated direction.
          if (direction < 0) {
               int newPosition = currentPosition - (currentPosition / maxUnitIncrement) * maxUnitIncrement;
               return (newPosition == 0) ? maxUnitIncrement : newPosition;
          else {
               return ((currentPosition / maxUnitIncrement) + 1) *     maxUnitIncrement - currentPosition;
     public int getScrollableBlockIncrement(Rectangle visibleRect, int orientation, int direction)
          if (orientation == SwingConstants.HORIZONTAL)
               return visibleRect.width - maxUnitIncrement;
          else
               return visibleRect.height - maxUnitIncrement;
     public boolean getScrollableTracksViewportWidth()
          return false;
     public boolean getScrollableTracksViewportHeight()
          return false;
     public void setMaxUnitIncrement(int pixels)
          maxUnitIncrement = pixels;
     public void setImage(ImageIcon icon) {
          image = icon.getImage();
          setPreferredSize(new Dimension(icon.getIconWidth(),icon.getIconHeight()));
     public void paintComponent(Graphics g) {
          super.paintComponent(g);
          if(image != null)
               g.drawImage(image, 0, 0, this);
}ScrollableGlassLabel:
public class ScrollableGlassLabel extends JLabel {
     private static Color[] colors = {
          Color.white, Color.black, Color.blue, Color.red, Color.yellow, Color.orange,
          Color.cyan, Color.pink, Color.magenta, Color.green };
     public ScrollableGlassLabel() {
          super();
          setOpaque(false);
     public void paintComponent(Graphics g) {
          int x, y, dx, dy;
          for(int i = 0; i < 32; i++) {
               x = (int)(Math.random()*100);
               y = (int)(Math.random()*100);
               dx = (int)(Math.random()*100);
               dy = (int)(Math.random()*100);
               g.setColor(colors[(int)(Math.random()*10)]);
               g.drawLine(x,y,x+dx,y+dy);
}Right now, it just draws random lines, but it will be drawing 3D meshes soon.
Thanks for you assistance, camickr. It at least got me thinking about alternatives.
Robert Templeton