Placing component on Glass Pane
- by Chris Lieb
I have a subclass of JLabel that forms a component of my GUI. I have implemented the ability to drag and drop the component from one container to another, but without any visual effects. I want to have this JLabel follow the cursor during the drag of the item from one container to another. I figured that I could just create a glass pane and draw it on there. However, even after I add the component to the glass pane, set the component visible, and set the glass pane visible, and set the glass pane as opaque, I still so not see the component. I know the component works because I can add it to the content pane and have it show up.
How do I add a component to the glass pane?
package wpics509s10t7.view;
import javax.swing.*;
import wpics509s10t7.model.Tile;
import java.awt.*;
import java.awt.dnd.DragSource;
import java.awt.event.AWTEventListener;
import java.awt.event.MouseEvent;
/**
* GlassPane tutorial
* "A well-behaved GlassPane"
* http://weblogs.java.net/blog/alexfromsun/
* <p/>
* This is the final version of the GlassPane
* it is transparent for MouseEvents,
* and respects underneath component's cursors by default,
* it is also friedly for other users,
* if someone adds a mouseListener to this GlassPane
* or set a new cursor it will respect them
*
* @author Alexander Potochkin
*/
public class GlassPane extends JPanel implements AWTEventListener {
private static final long serialVersionUID = 1L;
private final JFrame frame;
private TileView tv; // subclass of JLabel
private Point point;
private WordStealApp wsa;
public GlassPane(JFrame frame, WordStealApp wsa) {
super(null);
this.wsa = wsa;
this.frame = frame;
setOpaque(true);
setLayout(null);
setVisible(true);
composite = AlphaComposite.getInstance(AlphaComposite.SRC_OVER, 0.5f);
}
public void beginDrag(Tile t, Point p) {
this.tv = new TileView(t, null, this.wsa, true);
this.add(this.tv);
System.out.println("Starting point: x=" + p.getX() + ",y=" + p.getY());
this.tv.setLocation((int)p.getX(), (int)p.getY());
this.tv.setVisible(true);
}
public void endDrag(Point p) {
System.out.println("Ending point: x=" + p.getX() + ",y=" + p.getY());
this.remove(this.tv);
this.tv.setVisible(false);
this.tv = null;
}
public void eventDispatched(AWTEvent event) {
if (event instanceof MouseEvent) {
MouseEvent me = (MouseEvent) event;
if (!SwingUtilities.isDescendingFrom(me.getComponent(), frame)) {
return;
}
if (me.getID() == MouseEvent.MOUSE_EXITED && me.getComponent() == frame) {
if (tv != null) {
tv.setVisible(false);
}
point = null;
} else {
MouseEvent converted = SwingUtilities.convertMouseEvent(me.getComponent(), me, frame.getGlassPane());
point = converted.getPoint();
}
repaint();
}
}
/**
* If someone adds a mouseListener to the GlassPane or set a new cursor
* we expect that he knows what he is doing
* and return the super.contains(x, y)
* otherwise we return false to respect the cursors
* for the underneath components
*/
@Override
public boolean contains(int x, int y) {
if (getMouseListeners().length == 0 && getMouseMotionListeners().length == 0
&& getMouseWheelListeners().length == 0
&& getCursor() == Cursor.getPredefinedCursor(Cursor.DEFAULT_CURSOR)) {
return false;
}
return super.contains(x, y);
}
}
