Sharing tabs between 2 JFrames

• download example.jar
• download src.zip
• repository

Code

//Display "DropLocation" using JLayer 
class DropLocationLayerUI extends LayerUI {
  private static final int LINEWIDTH = 3;
  private final Rectangle lineRect = new Rectangle();
  @Override public void paint(Graphics g, JComponent c) {
    super.paint (g, c);
    JLayer layer = (JLayer)c;
    DnDTabbedPane tabbedPane = (DnDTabbedPane)layer.getView();
    DnDTabbedPane.DropLocation loc = tabbedPane.getDropLocation();
    if(loc != null && loc.isDropable() && loc.getIndex()>=0) {
      int index = loc.getIndex();
      boolean isZero = index==0;
      Rectangle r = tabbedPane.getBoundsAt(isZero?0:index-1);
      if(tabbedPane.getTabPlacement()==JTabbedPane.TOP ||
         tabbedPane.getTabPlacement()==JTabbedPane.BOTTOM) {
        lineRect.setRect(
            r.x-LINEWIDTH/2+r.width*(isZero?0:1), r.y,LINEWIDTH,r.height);
      }else{
        lineRect.setRect(
            r.x,r.y-LINEWIDTH/2+r.height*(isZero?0:1), r.width,LINEWIDTH);
      }
      Graphics2D g2 = (Graphics2D)g.create();
      g2.setComposite(AlphaComposite.getInstance(AlphaComposite.SRC_OVER, 0.5f));
      g2.setColor(Color.RED);
      g2.fill(lineRect);
      g2.dispose();
    }
  }
}

private final JLabel label = new JLabel() {
// https://free-the-pixel.blogspot.com/2010/04/ghost-drag-and-drop-over-multiple.html
// Free the pixel: GHOST drag and drop, over multiple windows]
  @Override public boolean contains(int x, int y) {
    return false;
  }
};
private final JWindow dialog = new JWindow();
public TabTransferHandler() {
  dialog.add(label);
  //dialog.setAlwaysOnTop(true); // Web Start
  dialog.setOpacity(0.5f);
  //com.sun.awt.AWTUtilities.setWindowOpacity(dialog, 0.5f); // JDK 1.6.0
  DragSource.getDefaultDragSource().addDragSourceMotionListener(
      new DragSourceMotionListener() {
    @Override public void dragMouseMoved(DragSourceDragEvent dsde) {
      Point pt = dsde.getLocation();
      pt.translate(5, 5); // offset
      dialog.setLocation(pt);
    }
  });
//...

References

• Sharing tabs between 2 JFrames(Japanese)
• Free the pixel: GHOST drag and drop, over multiple windows