[platform-dev] a plugin question: can not get the bundle!

["liu william" <caeserwliu@xxxxxxxxxxx>]

Hi all:

I am working on my first plugin demo, the plugin.xml and the manifast.mf 
are followed:
plugin.xml:
<?xml version="1.0" encoding="UTF-8"?>
<?eclipse version="3.2"?>
<plugin>
   <extension
        	point="org.eclipse.ui.perspectives">
       <perspective
      	    	name="myplugin demo"
           	icon="icons/selectall.gif"
           	class="myplugindemo.SamplePerspective"
           	id="myplugindemo.SamplePerspective">
       </perspective>
   </extension>
	<extension 
			point="org.eclipse.ui.views">
		<category 
				name="myplugin demo 视图"
				id="myplugindemo.view">
		</category>
		<view
				name="view 1"
				icon="icons/prev.gif"
				category="myplugindemo.view"
				class="myplugindemo.View1"
				id="myplugindemo.View1">
		</view>
		<view
				name="view 2"
				icon="icons/project.gif"
				category="myplugindemo.view"
				class="myplugindemo.View2"
				id="myplugindemo.View2">
		</view>
	</extension>
	<extension
  			point="org.eclipse.ui.editors">
  		<editor
  				name="中国 editor"
  				icon="icons/project.gif"
  				class="myplugindemo.ChinaEditor"
  				id="myplugindemo.ChinaEditor">	
  		</editor>
  		<editor
  				name="US editor"
  				icon="icons/prev.gif"
  				class="myplugindemo.UsEditor"
  				id="myplugindemo.UsEditor">	
  		</editor>
  		<editor
  				name="France editor"
  				icon="icons/remove.gif"
  				class="myplugindemo.FranceEditor"
  				id="myplugindemo.FranceEditor">	
  		</editor>
	</extension>
	<extension
			point="org.eclipse.ui.preferencePages">
		<page
				name="myplugindemo config"
				class="myplugindemo.preferences.RootPreferencePage"
				id="myplugindemo.preferences.RootPreferencePage">
		</page>
		<page
				name="DB config"
				category="myplugindemo.preferences.RootPreferencePage"
				class="myplugindemo.preferences.DBPreferencePage"
				id="myplugindemo.preferences.DBPreferencePage">
		</page>
	</extension>
</plugin>
manifest.mf:
Manifest-Version: 1.0
Bundle-ManifestVersion: 2
Bundle-Name: MyPluginDemo Plug-in
Bundle-SymbolicName: MyPluginDemo;singleton:=true
Bundle-Version: 1.0.0
Bundle-Activator: myplugindemo.Activator
Bundle-Localization: plugin
Require-Bundle: org.eclipse.ui,
org.eclipse.core.runtime
Eclipse-LazyStart: false

the perspectives/views/editors are all ok, but the preferencePages can not 
be initialed because the Activator.getDefault() returns null.
the preferencePages and the Activator are followed:

public class Activator extends AbstractUIPlugin {

	public static final String PLUGIN_ID = "MyPluginDemo";

	private static Activator plugin;
	
	public Activator() {
		super();
		plugin = this;
	}

	public void start(BundleContext context) throws Exception {
		super.start(context);
	}

	public void stop(BundleContext context) throws Exception {
		plugin = null;
		super.stop(context);
	}

	public static Activator getDefault() {
		return plugin;
	}

}

public class DBPreferencePage extends PreferencePage implements
		IWorkbenchPreferencePage, ModifyListener {
   ......
	public void init(IWorkbench workbench) {
		setPreferenceStore(Activator.getDefault().getPreferenceStore());
	}
   ......
}

the error log :
!ENTRY org.eclipse.jface 4 2 2006-08-21 15:48:43.125
!MESSAGE Problems occurred when invoking code from plug-in: 
"org.eclipse.jface".
!STACK 0
java.lang.NullPointerException
	at 
myplugindemo.preferences.DBPreferencePage.init(DBPreferencePage.java:98)
	at 
org.eclipse.ui.internal.dialogs.WorkbenchPreferenceNode.createPage(WorkbenchPreferenceNode.java:57)

	......


I don't know this is a bug or sth. else. Whatever, Please tell me how to 
solve the problem and tell me why. Thank you a lot!

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