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From "Alexei Fedotov" <alexei.fedo...@gmail.com>
Subject Re: [classlib][swing] the method called via reflection in UIDefaults is undefined Re: JRootPane NPE
Date Fri, 04 Apr 2008 18:01:09 GMT
Tharindu,
Yes, learning basics is a proper thing to do. I found your article
much better than the book I had read [1].

[1] Kathy Walrath, Mary Campione The JFC Swing Tutorial
http://books.google.com/books?id=3rWTX-vjUhEC&printsec=frontcover

On Fri, Apr 4, 2008 at 8:59 PM, Tharindu Mathew <mccloud35@gmail.com> wrote:
> Before digging deep on the problem, I feel I should understand the Swing
>  subsystem more. I'm reading the following article to get a proper idea.
>
>  http://java.sun.com/products/jfc/tsc/articles/architecture/
>
>  Please tell me if there is more relevant articles that will help me along
>  the way. Thanks for the help.
>
>
>  On Fri, Apr 4, 2008 at 7:17 PM, Alexei Fedotov <alexei.fedotov@gmail.com>
>  wrote:
>
>
>
>  > Tharindu,
>  > Thanks for the question. If I understand you correctly UIDefaults hash
>  > table does not contain a proper value for a method to call for the key
>  > corresponding to JRootPane.class. Why? The brief answer is "I don't
>  > know". Keep digging deeper. BTW, do we have swing gurus on the list
>  > who could shed the light on the problem?
>  >
>  > To guess what should be in the method variable I suggest you setting a
>  > breakpoint on this line and try to collect a statistics for working
>  > swing demos. Why do they work? If JRootPanne would work, it probably
>  > has a different look and feel or setup in standard demos.
>  >
>  > I like that you have come with the guess. I checked how setUI() is
>  > called from java/common/javax/swing/JRootPane.java: it is mentioned
>  > three times as in other components. So, keeping an eye on this method
>  > does not help. I believe someone should register a method for this
>  > class in UIDefaults, for example, call new UIDefaults(a proper array).
>  > I found that this is done in the following places.
>  >
>  > $  grep -rlI 'new UIDefaults' ./java/common/javax/swing/* | grep -v svn
>  > ./java/common/javax/swing/LookAndFeel.java
>  > ./java/common/javax/swing/UIManager.java
>  > ./java/common/javax/swing/plaf/basic/BasicLookAndFeel.java
>  > ./java/common/javax/swing/plaf/metal/MetalLookAndFeel.java
>  > ./java/common/javax/swing/plaf/multi/MultiLookAndFeel.java
>  > ./java/common/javax/swing/plaf/synth/SynthLookAndFeel.java
>  > ./java/common/javax/swing/text/AbstractDocument.java
>  >
>  > Based on this list I may guess that the chosen look and feel does not
>  > register JRootPane look and feel correctly. Please, keep us posted on
>  > your advances.
>  >
>  > Thanks!
>  >
>  > On Fri, Apr 4, 2008 at 10:12 AM, Tharindu Mathew <mccloud35@gmail.com>
>  > wrote:
>  > > ERROR: UIDefaults.getUI() failed: java.lang.NullPointerException
>  > >     at javax.swing.UIDefaults.getUI(UIDefaults.java:339)
>  > >     at javax.swing.UIManager.getUI(UIManager.java:222)
>  > >     at javax.swing.JPanel.updateUI(JPanel.java:141)
>  > >     at javax.swing.JPanel.<init>(JPanel.java:56)
>  > >     at javax.swing.JPanel.<init>(JPanel.java:76)
>  > >     at javax.swing.JRootPane.createGlassPane(JRootPane.java:278)
>  > >     at javax.swing.JRootPane.<init>(JRootPane.java:78)
>  > >     at javax.swing.JFrame.createRootPane(JFrame.java:175)
>  > >     at javax.swing.JFrame.frameInit(JFrame.java:393)
>  > >     at javax.swing.JFrame.<init>(JFrame.java:123)
>  > >     at
>  > >
>  >  net.sf.freecol.client.gui.FullScreenFrame.<init>(FullScreenFrame.java:34)
>  > >     at
>  > net.sf.freecol.client.FreeColClient.startGUI(FreeColClient.java:218)
>  > >     at
>  > net.sf.freecol.client.FreeColClient.access$000(FreeColClient.java:31)
>  > >     at net.sf.freecol.client.FreeColClient$1.run(FreeColClient.java:142)
>  > >     at
>  > java.awt.event.InvocationEvent.runAndNotify(InvocationEvent.java:98)
>  > >     at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:78)
>  > >     at
>  > java.awt.EventQueueCore.dispatchEventImpl(EventQueueCore.java:138)
>  > >     at java.awt.EventQueue.dispatchEvent(EventQueue.java:144)
>  > >     at
>  > >  java.awt.EventDispatchThread.runModalLoop(EventDispatchThread.java:74)
>  > >     at java.awt.EventDispatchThread.run(EventDispatchThread.java:48)
>  > >
>  > >
>  > >  In the UI defaults class:
>  > >
>  > >   Method method = null;
>  > >             if (uiClass == null) {
>  > >                 uiClass = getUIClass(classID,
>  > >  comp.getClass().getClassLoader());
>  > >                 method = getCreateUIMethodPriveledged(uiClass);
>  > >
>  > >                 put(fullClassName, uiClass);
>  > >                 put(uiClass, method);
>  > >             } else {
>  > >                 method = (Method)get(uiClass); *<--- method is null,
>  > because
>  > >  no value exists for the uiClass key*
>  > >             }
>  > >             return (ComponentUI)method.invoke(null, new Object[] { comp
>  > });
>  > >  *<--- causes NPE when tryin to invoke*
>  > >
>  > >  What is supposed to return to the method variable? Does this return
>  > null
>  > >  because the setUI() method is not called from within JRootPane?
>  > >
>  > >  --
>  > >  Regards,
>  > >
>  > >  Tharindu
>  > >
>  >
>  >
>  >
>  > --
>  > With best regards,
>  > Alexei
>  >
>
>
>
>  --
>  Regards,
>
>  Tharindu
>



-- 
With best regards,
Alexei

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