Problems with CellRendererP(AIN)ane

Question

Hi,
I have a serious problem in using the CellRendererPane when drawing components in a Panel.
See this code fragment:
public class A_PANEL extends JPanel
private MyPanel myPanel = new MyPanel(); /* --> setOpaque(true) was invoked in this class during init*/
private CellRendererPane CRP = new CellRendererPane();
public void paintComponent(Graphics g) {
CRP.paintComponent( g,
myPanel,
this,
50,
50,
100,
100,
true);
The problems occurs as follows: The sub-components in "MyPanel" ( a button, a label and some other Swing components) are NOT shown in "A_PANEL". Only a rectangle with the size of the panel ("MayPanel") itself is painted and no other sub-components. If I set overwrite "isShowing" in "MyPanel" and unconditionally return true, a nullpointerexception occurs:
Exception in thread "main" java.lang.NullPointerException
at javax.swing.JComponent.reshape(JComponent.java:2728)
at java.awt.Component.setBounds(Component.java:1269)
at java.awt.Component.resize(Component.java:1206)
at java.awt.Component.setSize(Component.java:1198)
at abcassy.concepts.graph.RendererTestPanel.<init>(Renderer
at abcassy.concepts.graph.DefaultVertexRenderer.<init>(Defa
at abcassy.concepts.graph.JGraph.<init>(JGraph.java:17)
at abcassy.JGraphTestFrame.<init>(JGraphTestFrame.java:104)
at abcassy.JGraphTestFrame.main(JGraphTestFrame.java:112)

Answer 1

Why are you using this approach? What you are doing is overriding the normal paint method of the content pane and replacing it with an empty component. This is behaving exactly as I would expect -- the CellRendererPane is empty and will appear as a blank rectangle.
Mitch Goldstein
Author, Hardcore JFC (Cambridge Univ Press)
[email protected]