Name: dbT83986 Date: 08/21/99


If you call Component.requestFocus() on a lightweight component in a window that is not active, you will never get a FOCUS_GAINED event on that component. LightWeightDispatcher.setFocusRequest() will not dispatch a FOCUS_GAINED, and Container.proxyRequestFocus() will not call requestFocus() on the heavyweight container. So nothing happens and the call to requestFocus() is essentially ignored.

The fix for the problem is very simple, it is to simply add a call to setFocusOwner() in Container.proxyRequestFocus(), so it looks like this:

if ( isContainingWindowActivated() ) {
    requestFocus();
} else {
    setFocusOwner(c);
}

You don't want to call requestFocus() in this case, because it could potentially activate an inactive window, but you do need to set the focus owner so that when the window does become active, focus will go to the component.

A test case is included below. It uses a very simple lightweight component which draws itself as a circle, and draws a crosshair in the circle when it has focus. When you run the test, the window should come up with the component focused, but it does not. The circle is empty. The test has a focus listener which will put a message in the console whenver a focusGained is received, but if you look at the console you will not see this message.

This did not reproduce in JDK 1.1.5, because the FOCUS_GAINED was dispatched in LightWeightDispatcher.setFocusRequest(). This is not correct, however, as you will see if you run this test case with 1.1.5: the component will get TWO focusGained events, one before the window is activated and one after. The above solution, where you simply call setFocusOwner(), gives you only one focusGained after the windowActivated, which is the correct behavior.

The test case follows:

import java.awt.*;
import java.awt.event.*;
public class FocusTest extends Frame implements WindowListener
{
static public void main(String[] args) {
(new FocusTest()).setVisible(true);
}
public FocusTest() {
super("Focus Test");
Panel panel = new Panel();
add(panel);
LightWeight lw = new LightWeight();
addWindowListener(this);
panel.add(lw);
pack();
lw.requestFocus();
}
public void windowOpened(WindowEvent e){}
public void windowClosing(WindowEvent e) {
System.exit(0);
}
public void windowClosed(WindowEvent e){}
public void windowIconified(WindowEvent e){}
public void windowDeiconified(WindowEvent e){}
public void windowActivated(WindowEvent e) {
System.out.println("windowActivated");
}
public void windowDeactivated(WindowEvent e){
System.out.println("windowDeactivated");
}

// A very simple lightweight component
class LightWeight extends Component implements FocusListener {

boolean focused = false;

public LightWeight() {
addFocusListener(this);
}

public void paint(Graphics g) {
Dimension size = getSize();
int w = size.width;
int h = size.height;
g.drawOval(0, 0, w-1, h-1);
if (focused) {
g.drawLine(w/2, 0, w/2, h);
g.drawLine(0, h/2, w, h/2);
}

}

public Dimension getPreferredSize() {
return new Dimension(150, 150);
}

public void focusGained(FocusEvent e) {
focused = true;
System.out.println("focusGained");
repaint();
}

public void focusLost(FocusEvent e) {
focused = false;
System.out.println("focusLost");
repaint();
}

        }
}
(Review ID: 94151)
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