my internalframe freezes with an IllegalArgumentException for its second time open

[Zamioculcas]

My "singleton typed" internalframe freezes with an IllegalArgumentException for its second time open

Hi everybody,

I created a singleton window (I try to use the Singleton pattern), which extends a JInternalFrame. Subsequently I add it within a JFrame. If I open the internalframe for second time I would like to get the focus to the already opened JInternalFrame.

But now I get an IllegalArumentException and my internalframe freezes.

What is wrong my code?
Might I made some mistakes, in my singleton class?

I would be very grateful if someone could help me!
Thanks in advance.


the following code contains my singleton class:

import javax.swing.*;
public class SingletonDemo extends JInternalFrame{
private SingletonDemo()
	{
			super("ff",true,true,true,true);
			setSize(100,100);
			setTitle("Singleton");
			setDefaultCloseOperation(JInternalFrame.DISPOSE_ON_CLOSE);
	}
private static SingletonDemo myInstance;
public static SingletonDemo getInstance () throws IllegalArgumentException
	{
		if (myInstance == null)
			{
				myInstance = new SingletonDemo();
			}
		return myInstance;
	}
}

here is my class which contains the main frame with the menus:
You try to click the "singleton frame" menuitem again, when the internalframe window is already opened.

import javax.swing.*;
import java.awt.event.*;
public class MyFrame extends JFrame implements ActionListener{
	JMenuBar menubar = new JMenuBar();
	JMenu menu  = new JMenu("menu");
	JMenuItem singleton = new JMenuItem("singleton frame");
	final JDesktopPane desk = new JDesktopPane();
	public MyFrame()
		{
			setSize(350,350);
			setTitle("Singleton");
			setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
			setJMenuBar(menubar);
			menubar.add(menu);
			menu.add(singleton);
			singleton.addActionListener(this);
			getContentPane().add(desk);
			setVisible(true);
		}
	public void actionPerformed(ActionEvent e) throws IllegalArgumentException
		{
			try
			{
			if (e.getActionCommand().equals("singleton frame"))
				{
					System.out.println("open singleton frame");
					SingletonDemo sing = SingletonDemo.getInstance();
					desk.add(sing);
					sing.setVisible(true);
					
				}
			}
			catch(IllegalArgumentException iae)
			{
				System.out.println("illegalargumentexception...");
				iae.printStackTrace();
			}
		}
	public static void main(String[] args)
		{
			new MyFrame();
		} }

[Norm]

Please copy and paste here the full text of the error message.

[Norm]

For a test try adding sing twice. You'll get the same error quicker:

					desk.add(sing);
                                        desk.add(sing);   // For a test add it again - to demo the error!!
					sing.setVisible(true);

[Zamioculcas]

Hi Norm,

thanks your promp reflection. I inserted a new line to my code, that you mentioned before.
And now I get a same exception message at the first try.

here is my full exception message, I hope this helps:

java.lang.IllegalArgumentException: illegal component position
at java.awt.Container.addImpl(Unknown Source)
at javax.swing.JLayeredPane.addImpl(Unknown Source)
at javax.swing.JDesktopPane.addImpl(Unknown Source)
at java.awt.Container.add(Unknown Source)
at MyFrame.actionPerformed(MyFrame.java:28)
at javax.swing.AbstractButton.fireActionPerformed(Unk nown Source)
at javax.swing.AbstractButton$Handler.actionPerformed (Unknown Source)
at javax.swing.DefaultButtonModel.fireActionPerformed (Unknown Source)
at javax.swing.DefaultButtonModel.setPressed(Unknown Source)
at javax.swing.AbstractButton.doClick(Unknown Source)
at javax.swing.plaf.basic.BasicMenuItemUI.doClick(Unk nown Source)
at javax.swing.plaf.basic.BasicMenuItemUI$Handler.mou seReleased(Unknown
Source)
at java.awt.Component.processMouseEvent(Unknown Source)
at javax.swing.JComponent.processMouseEvent(Unknown Source)
at java.awt.Component.processEvent(Unknown Source)
at java.awt.Container.processEvent(Unknown Source)
at java.awt.Component.dispatchEventImpl(Unknown Source)
at java.awt.Container.dispatchEventImpl(Unknown Source)
at java.awt.Component.dispatchEvent(Unknown Source)
at java.awt.LightweightDispatcher.retargetMouseEvent( Unknown Source)
at java.awt.LightweightDispatcher.processMouseEvent(U nknown Source)
at java.awt.LightweightDispatcher.dispatchEvent(Unkno wn Source)
at java.awt.Container.dispatchEventImpl(Unknown Source)
at java.awt.Window.dispatchEventImpl(Unknown Source)
at java.awt.Component.dispatchEvent(Unknown Source)
at java.awt.EventQueue.dispatchEvent(Unknown Source)
at java.awt.EventDispatchThread.pumpOneEventForFilter s(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForFilter(U nknown Source)
at java.awt.EventDispatchThread.pumpEventsForHierarch y(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.run(Unknown Source)

[Norm]

What my simple test demonstrates, I think, is that you can NOT add the same instance of a component to a container more than once.
Your design is flawed.

[Zamioculcas]

Thanks for your quick response again. I investigated a bit more what you demonstrated in your comments.
I took into account what you mentioned, so we can't add the instance of the component to the container more than once, thanks to my homebrew singleton class.
I scratched my head and It took me a long time but I have solved the problem:)

I placed into the problematic line "desk.add(sing);" into a IF condition. If the internalframe is invisible, it would be added to the container.
So I avoid adding an instance of component to a container more than once.

I declared my singleton objects outside the function:
SingletonDemo sing = SingletonDemo.getInstance();

And here is my code snippet, which contains the my solution:

public void actionPerformed(ActionEvent e) throws IllegalArgumentException
		{
			try
			{
			if (e.getActionCommand().equals("singleton frame"))
				{
				   if (sing.isVisible())
					{
						System.out.println("frame is already opened...");
					}		
				   else
					{	
						System.out.println("open singleton frame");
						desk.add(sing);
						sing.setVisible(true);
					}
					
				}
			}
			catch(IllegalArgumentException iae)
			{
				System.out.println("illegalargumentexception...");
				iae.printStackTrace();
			}
		}