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Error when using addComponentListener in a getter [message #777361]

Tue, 10 January 2012 10:38

Rayleigh Missing name

Messages: 20
Registered: July 2011

Junior Member

The following example shows a blank screen in Window Builder:

import javax.swing.JFrame;


public class Frame extends JFrame{
	
	private JPanel panel;
	
	public Frame(){
		super();
		initialize();
	}
	
	private void initialize() {
		this.setName("ABC");
		this.setLocation(0, 10);
		this.setSize(990, 750);
		this.setTitle("abc");
		this.setContentPane(this.getPanel());
	}
	
	protected JPanel getPanel() {
		if (panel == null) {
			panel = new JPanel();
			
			JLabel lblTest = new JLabel("lala");
			panel.add(lblTest);
			
		}
		panel.addComponentListener(new java.awt.event.ComponentAdapter() {
			public void componentResized(java.awt.event.ComponentEvent e) {
				// abc
			}
		});
		
		return panel;
	}
}

But if panel.addComponentListener is moved into the if block, it works

protected JPanel getPanel() {
		if (panel == null) {
			panel = new JPanel();
			
			JLabel lblTest = new JLabel("lala");
			panel.add(lblTest);
			
			panel.addComponentListener(new java.awt.event.ComponentAdapter() {
				public void componentResized(java.awt.event.ComponentEvent e) {
					// abc
				}
			});
		}
		
		return panel;
	}

Is it possible to get it working without touching the code? We've got a lot of legacy code that isn't even ours and we can't check and update a thousand panels.

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Re: Error when using addComponentListener in a getter [message #777561 is a reply to message #777361]

Tue, 10 January 2012 17:48

Konstantin Scheglov

Messages: 555
Registered: July 2009

Senior Member

Rayleigh Mising name wrote on Tue, 10 January 2012 05:38

Is it possible to get it working without touching the code? We've got a lot of legacy code that isn't even ours and we can't check and update a thousand panels.

In theory - yes.
Practically this is violation of lazy pattern and I don't want to include this into WindowBuilder codebase.

If you want, you could make your custom version with tweaked

org.eclipse.wb.internal.core.model.variable.LazyVariableSupportUtils.getInformation(MethodDeclaration)

method.

Konstantin Scheglov,
Google, Inc.

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Re: Error when using addComponentListener in a getter [message #777587 is a reply to message #777361]

Tue, 10 January 2012 19:08

Eric Clayberg

Messages: 975
Registered: July 2009
Location: Boston, MA

Senior Member

Rayleigh Mising name wrote on Tue, 10 January 2012 05:38

Is it possible to get it working without touching the code? We've got a lot of legacy code that isn't even ours and we can't check and update a thousand panels.

You really should fix this code. As written, having panel.addComponentListener outside of the if block is very bad and will lead to the same listener being added multiple times (a serious bug). This is not something we want to encourage or support. If you are going to use the lazy pattern, use it correctly.

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