UIManager & Custom UIs

Question

In my test application I have:
- A custom LookAndFeel installed (extends MetalLookAndFeel)
- GreenPanelUI and RedPanelUI which both extend BasicPanelUI
Their paint methods draw a small green or red square in top left of the panel.
- MyPanel which extends JPanel and uses GreenPanelUI as its default UI.
- In my application JFrame I have:
1 an instance of JPanel
2 an instance of JPanel with setBackground(Color.red);
3 an instance of MyPanel
4 an instance of JPanel with setUI(RedPanelUI) & setBackground(Color.yellow)
- There is also an editor which enables the user to change the UIDefaults for Panel.background. Everytime this is done SwingUtilities.updateComponentTreeUI( <my test app> ) is called to update the colours.
When I start my app everything is fine and works as expected
1 is grey - as expected from subclassing MetalLookAndFeel
2 is red
3 is grey with a green square
4 is yellow with a red square
Now when things go wrong is when the user chooses a new colour Panel.background. i.e.
UIManager.put("Panel.background", new ColorUIResource(Color.blue));
SwingUtilities.updateComponentTreeUI( <my test app> );
Now;
1 is blue - GOOD
2 is red - GOOD
3 is blue with a green square - GOOD
4 is yellow - BAD
Okay, I presume the SwingUtilities.updateComponentTreeUI has caused the default UI to be reinstalled for each JPanel.
This where my knowledge and understanding of the use and scope of UIManager & L&F is lacking, 'cos what I'd like to do is call the setUI method on numerous instances of JPanel to install numerous different PanelUIs (which I know does work).
However, this business of SwingUtilities.updateComponentTreeUI resetting the UI delegate is, for me in this case, annoying.
It seems as if the only to keep the UI delegate is to subclass the JPanel and set its default UI with the UIManager. Therefore if I wish to display 5 Panels each with a different PanelUI then I must also create 5 different Panel subclasses. Surely this can't be right!!!
Would appreciate any help or thoughts on this one.
Thanks

Answer 1

Any UI specialists out there? Please? Help??