Not Possible in Java ? : drop-up JComboBox

[raphael Bereh]

Went through old post and saw the question raised more than once, and no solution !
Well I need my Combo Box list to drop Up instead of down !
Any Swing guru to help ?

[Eric Snell]

Originally posted by raphael Bereh:
Well I need my Combo Box list to drop Up instead of down !

Here's a subclass of MetalComboBoxUI that pops up above the combo:

  
import javax.swing.plaf.basic.BasicComboPopup;
import javax.swing.plaf.basic.ComboPopup;
import javax.swing.plaf.metal.MetalComboBoxUI;
 
import java.awt.Rectangle;
 
public class PopUpMetalComboBoxUI extends MetalComboBoxUI {
 
   protected ComboPopup createPopup() {
      return new BasicComboPopup(comboBox) {
         protected Rectangle computePopupBounds(int px, int py, int pw, int ph) {
            Rectangle rect = super.computePopupBounds(px, py, pw, ph);
            rect.y = -rect.height;
            return rect;
         }
      };
   }
}
 

Install the UI in your combo with:

 
combo.setUI(new PopUpMetalComboBoxUI());

Now the problems:
1. If the popup will be off the screen, it is moved down. A better solution would be to allow it to drop down instead. See the implementation of BasicComboPopup.computePopupBounds for example code to do this.
2. This solution requires you to subclass a specific ComboBoxUI. I think it would have been better to delegate so as to make the solution applicable to any UI. The only way I see of getting acces to the popup in BasicComboBoxUI is subclassing or reflection. So I can't get the current popup to delegate to it.

Anyway, this solution is relatively simple and you can customize it as necessary.

[raphael Bereh]

Looks greate,
Thanks Eric,

[Ko Ko Naing]

Yeah, it's really kool... And it's worthful to know such thing for me...