Java and Windows Look & feel

Question

I made a swing application that scans Images; and each Image represented by a leaf I a tree

the problem that I faced is that it throws this exception

Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
    at com.sun.java.swing.plaf.windows.XPStyle$Skin.getWidth(XPStyle.java:513)
    at com.sun.java.swing.plaf.windows.XPStyle$Skin.getWidth(XPStyle.java:517)
    at com.sun.java.swing.plaf.windows.WindowsTreeUI$ExpandedIcon.getIconWidth(WindowsTreeUI.java:138)
    at javax.swing.plaf.basic.BasicTreeUI.drawCentered(BasicTreeUI.java:1580)
    at javax.swing.plaf.basic.BasicTreeUI.paintExpandControl(BasicTreeUI.java:1464)
    at javax.swing.plaf.basic.BasicTreeUI.paint(BasicTreeUI.java:1206)
    at javax.swing.plaf.ComponentUI.update(ComponentUI.java:143)
    at javax.swing.JComponent.paintComponent(JComponent.java:763)
    at javax.swing.JComponent.paint(JComponent.java:1027)
    at javax.swing.JComponent.paintToOffscreen(JComponent.java:5122)
    at javax.swing.BufferStrategyPaintManager.paint(BufferStrategyPaintManager.java:285)
    at javax.swing.RepaintManager.paint(RepaintManager.java:1128)
    at javax.swing.JComponent._paintImmediately(JComponent.java:5070)
    at javax.swing.JComponent.paintImmediately(JComponent.java:4880)
    at javax.swing.RepaintManager.paintDirtyRegions(RepaintManager.java:723)
    at javax.swing.RepaintManager.paintDirtyRegions(RepaintManager.java:679)
    at javax.swing.RepaintManager.seqPaintDirtyRegions(RepaintManager.java:659)
    at javax.swing.SystemEventQueueUtilities$ComponentWorkRequest.run(SystemEventQueueUtilities.java:128)
    at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:209)
    at java.awt.EventQueue.dispatchEvent(EventQueue.java:597)
    at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:273)
    at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:183)
    at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:173)
    at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:168)
    at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:160)
    at java.awt.EventDispatchThread.run(EventDispatchThread.java:121)

and I don't know why this appears Note: I am using Windows Look and feel

UIManager.setLookAndFeel("com.sun.java.swing.plaf.windows.WindowsLookAndFeel");

and java 1.6_22 under windows-7

Nuncupative

Can you post your code please? It's hard to tell what's going on without the code. – Knowles

can you post the source code? – Autogenous

I do not believe the problem is with the library itself. Do you mind sharing how you are scanning for images in directory. I sense problem with input. ( list of images in dir) – Columbian

Actually, I could well believe this is a problem with the Windows PL&F. A minimal example of code that triggers the problem would be good. Possibly it is quite machine specific. – Dialectician

UIManager.setLookAndFeel("com.sun.java.swing.plaf.windows.WindowsLookAndFeel"); // Bad, Bad, Bad UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName()); // good, good, good - Your version will not work on anything but Windows, not that Mac and Unix users would want to see Windows PLAF on their desk-top in any case. As to the suggestion to 'post code' - I 'downvote' that. Instead post an SSCCE (pscode.org/sscce.html). Also, my WAG is that the code is doing something off the EDT, that should be done on the EDT. – Aeneas

Just use SWT... the Swing implementation on Windows 7 sucks anyway. – Weltanschauung

Did you set the look and feel before or after the component's frame was visible? I vaguely remember getting this nullpoiner when changing the look and feel to WindowsLookAndFeel if a frame was already visible. – Immunotherapy

@Lucass PLAF can be changed when a JFrame (or JApplet) is already visible. It is just necessary to call SwingUtilities.updateComponentTreeUI(Component) to ensure the tree of components is adjusted. – Aeneas

I used UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName() first but still problem found. and also it is the first line in my main()method – Nuncupative

Answer 1

Try this:

//Set the look and feel to users OS LaF.
    try {
        UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
    } catch (ClassNotFoundException e) {
        e.printStackTrace();
    } catch (InstantiationException e) {
        e.printStackTrace();
    } catch (IllegalAccessException e) {
        e.printStackTrace();
    } catch (UnsupportedLookAndFeelException e) {
        e.printStackTrace();
    }

Teletype

"//Set the look and feel to windows." No it does not do that. At least, not on a Mac. or *nix OS. – Aeneas

Oh my god I love it. On windows this looks AWESOME. – Indiscriminate

Please consider voting the answer up if it helped you. – Teletype

Why not catch (Exception e)? – Brassard

WChargin: the try catch blocks were probably generated individually by the IDE (eclipse behaves like this). – Stylistic