Name: wm7046 Date: 06/12/97


The following code exhibits a problem in event handling for
lightweight components. Clicking on the red square should produce a MouseClicked event nothing happens. The reason is that the double addNotify() calls clear the event mask within the container. Removing one of the addNotify() calls fixes the problem.

This was seen in a dialog sublass that used addNotify() to gain access to FontMetrics. The second addNotify was done in the super class so was not under the control of the subclass.


Here is the sample code:


import java.awt.event.MouseEvent;
import java.awt.*;

public class EventTest extends java.awt.Dialog {

public EventTest() {
this(null);
}

public EventTest(String[] args) {
super(new java.awt.Frame(), "EventTest");
setLayout(null);
LightComponent l = new LightComponent();
add(l);
l.setBounds(50, 50, 100, 100);
addNotify();
addNotify();
setSize(600, 600);
setVisible(true);
}

public static void main(String[] args) {
new EventTest();
}

}


class LightComponent extends java.awt.Component
    implements java.awt.event.MouseListener
{
public LightComponent()
{
addMouseListener(this);
}

public void paint(Graphics g)
{
Dimension d = getSize();
g.setColor(Color.red);
g.fillRect(0,0,d.width, d.height);
}

public void mouseClicked(MouseEvent e)
{
System.out.println("Mouse Click");
}
public void mousePressed(MouseEvent e)
{
}
public void mouseReleased(MouseEvent e)
{
}
public void mouseEntered(MouseEvent e)
{
}
public void mouseExited(MouseEvent e)
{
}
}
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