Ubuntu中不能使用SystemLookAndFeel的问题

环境：Ubuntu 7, Java 6

在Ubuntu使用Java来编写Swing应用程序时一个比较大的问题就是不能使用SystemLookAndFeel。

import javax.swing.*;

public class DesktopApp {
	public static void main(String[] args) throws Exception {
		UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
		JFrame frame = new JFrame("My Frame");
		frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		frame.getContentPane().add(new JButton("Click"));
		frame.pack();
		frame.setVisible(true);
	}
}

运行抛出异常：

Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
	at com.sun.java.swing.plaf.gtk.GTKLookAndFeel.initSystemColorDefaults(GTKLookAndFeel.java:1267)
	at com.sun.java.swing.plaf.gtk.GTKLookAndFeel.loadStyles(GTKLookAndFeel.java:1509)
	at com.sun.java.swing.plaf.gtk.GTKLookAndFeel.access$000(GTKLookAndFeel.java:37)
	at com.sun.java.swing.plaf.gtk.GTKLookAndFeel$WeakPCL$1.run(GTKLookAndFeel.java:1449)
	at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:209)
	at java.awt.EventQueue.dispatchEvent(EventQueue.java:597)
	at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:273)
	at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:183)
	at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:173)
	at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:168)
	at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:160)
	at java.awt.EventDispatchThread.run(EventDispatchThread.java:121)
Exception in thread "main" java.lang.NullPointerException
	at javax.swing.plaf.synth.SynthLookAndFeel$AATextListener.propertyChange(SynthLookAndFeel.java:793)
	at java.beans.PropertyChangeSupport.firePropertyChange(PropertyChangeSupport.java:339)
	at java.beans.PropertyChangeSupport.firePropertyChange(PropertyChangeSupport.java:347)
	at java.beans.PropertyChangeSupport.firePropertyChange(PropertyChangeSupport.java:276)
	at java.awt.Toolkit.setDesktopProperty(Toolkit.java:1784)
	at sun.awt.SunToolkit.fireDesktopFontPropertyChanges(SunToolkit.java:1714)
	at sun.awt.SunToolkit.setAAFontSettingsCondition(SunToolkit.java:1759)
	at sun.swing.SwingUtilities2$AATextInfo.getAATextInfo(SwingUtilities2.java:119)
	at com.sun.java.swing.plaf.gtk.GTKLookAndFeel.initComponentDefaults(GTKLookAndFeel.java:1258)
	at com.sun.java.swing.plaf.gtk.GTKLookAndFeel.getDefaults(GTKLookAndFeel.java:294)
	at javax.swing.UIManager.setLookAndFeel(UIManager.java:537)
	at javax.swing.UIManager.setLookAndFeel(UIManager.java:581)
	at DesktopApp.main(DesktopApp.java:9)
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
	at com.sun.java.swing.plaf.gtk.GTKLookAndFeel.initSystemColorDefaults(GTKLookAndFeel.java:1267)
	at com.sun.java.swing.plaf.gtk.GTKLookAndFeel.loadStyles(GTKLookAndFeel.java:1509)
	at com.sun.java.swing.plaf.gtk.GTKLookAndFeel.access$000(GTKLookAndFeel.java:37)
	at com.sun.java.swing.plaf.gtk.GTKLookAndFeel$WeakPCL$1.run(GTKLookAndFeel.java:1449)
	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)

一种解决办法就是不使用SystemLookAndFeel，那么去掉

UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());

就可以了，或者将

System.setProperty("swing.systemlaf", "javax.swing.plaf.metal.MetalLookAndFeel");

添加到程序的最前面，那么表示即使调用UIManager.getSystemLookAndFeelClassName()也会返回CrossLookAndFeel。

如果确实要使用SystemLookAndFeel，可以在程序最前面添加：

UIManager.getLookAndFeelDefaults()

就能够看到SystemLookAndFeel，是不是很怪异？

上面讲的是可以改源码的情况下可以使用的方式，如果不能修改源码，那就只能在程序启动时传递-Dswing.systemlaf=javax.swing.plaf.metal.MetalLookAndFeel。比如对于groovy，如果不做任何设置，运行groovySh就会出现前面出现的异常，解决方法就是使用groovySh -Dswing.systemlaf=javax.swing.plaf.metal.MetalLookAndFeel。每次都输入这么长是很麻烦的，你可以修改bin目录下的startGroovy脚本，在脚本顶端添加：

JAVA_OPTS=-Dswing.systemlaf=javax.swing.plaf.metal.MetalLookAndFeel

这种方式应该对大多数java程序都适用，除非你特别钟情于SystemLookAndFeel。但不幸的是，对于"非java"程序（这里”非java"也包括并不是全部用java写的）,如果jconsole我就一直没有找到方法来启动它，不知大家有没有好的方法？

我本来想export swing.systemlaf=javax.swing.plaf.metal.MetalLookAndFeel，系统却抱怨swing.systemlaf不是一个合法的变量名，很是郁闷！

评论

3 楼 lifethinker 2008-07-26  

多谢ivan，在eclipse试了一下，果然是这样的，没想到还可以用这样的方式设置系统属性，学了一招。虽然现在已经改用kubuntu了，在kubuntu下没有这样的问题。

2 楼 ivan 2008-07-25  

可以修改 /etc/environment 文件在最后增加上：
_JAVA_OPTIONS="-Dswing.defaultlaf=javax.swing.plaf.metal.MetalLookAndFeel"

1 楼 无聊神灯 2008-06-06  

export LANG=en