AWT Canvas, Objects, and MouseListeners

[Cory Hartford]

Hi Everyone
I am working with an OSGI device that uses AWT as the GUI API. I've used it extensively but I have run across something that I can't figure out.
I have a component that I add a mouse listener to. I create an inner class that extends off of MouseAdapter to handle the events. In the mousePressed(MouseEvent e) method I use e.getSource() to get the component that fired the event.
I take that object and compare it to the original reference.

If I do this inside of a panel, everything is hunky dory. The objects are equal. However, when I place the same component into a panel that resides within a scroll pane, the objects don't test equal. Here are a couple of debug lines; the first is the source object from the MouseAdapter and the second line is the component object that I store when I instantiate it.

com.canon.meap.ctk.awt.CLabel[canvas23,420,44,67x20]
com.canon.meap.ctk.awt.CLabel[canvas24,420,44,67x20]

You can see that the canvases don't match and essentially I have two different objects. It has got to do with adding it to the panel in the scrollpane, but I don't understand why. It should be the same object; where I place it shouldn't make any difference.

Here are some code snippets that hopefully help illustrate what it is that I have



Build The ScrollPane and add the Panel

public void addWorkingScrollPanel(){
		workingPanelScrollPane = new ScrollPane(ScrollPane.SCROLLBARS_AS_NEEDED);
		workingPanelScrollPane.setBounds(203, 0, 597, 480);
		workingPanelScrollPane.setBackground(Color.CYAN);
		workingPanelScrollPane.setForeground(Color.BLACK);
		add(workingPanelScrollPane);
	}
	
	public void addWorkingPanel() {
		workingPanel = new Panel();
		workingPanel.setLayout(null);
		workingPanel.setBackground(Color.RED);
		workingPanel.setBounds(160, 0, 550, 500);
		workingPanelScrollPane.add(workingPanel);
	}

Instantiate the component

public void addUserIDValidateButton() {
		userIDValidate = new NQueueSmallButton(this.getClass().getClassLoader(), this.getToolkit(), ImagePaths.SMALL_BUTTON_BLANk_IMAGE,
				ImagePaths.SMALL_BUTTON_BLANk_IMAGE);
		workingPanel.add(userIDValidate.getLabel());
		workingPanel.add(userIDValidate);
		userIDValidate.addMouseListener (new TestListener());
		userIDValidate.getLabel().addMouseListener(new TestListener());

Handle the event

public class TestListener extends MouseAdapter {
		
		public void mousePressed(MouseEvent e) {
			System.out.println(e.getSource());
			System.out.println(userIDValidate.getLabel());
		}
	}

I guess that somehow adding the component to the panel within the scrollpane is somehow generating a new object and modifying it. That's the way it appears anyway. Just curious if someone can help me understand whats going on here. Thanks

[Claude Moore]

Mmm... just as workaround, what if you assign a name to the component and try and check names in you listener ?
This way you should get more hints about what happens under the hood... It looks strange a similar bug, even if with AWT on recent SO all may be possible..

[Cory Hartford]

Thanks for the response Claude. I tried that and much to my surprise instead of the name I assigned the component, I ended up getting a canvas name. So yeah it must be a bug. What I ended up doing was just creating individual listeners for each component; for some reasons the listeners persist even though the object is changed/recreated or whatever is happening.