如何解决这个java.lang.NoClassDefFoundError？

我在启动我的应用程序并单击android2.2中silding菜单中的一项列表时出现以下日志错误：

02-28 20:37:02.543    1107-1107/com.example.testnavigate
   E/dalvikvm: Could not find class 'com.example.testnavigate.MainActivity$PlanetFragment', referenced from method com.example.testnavigate.MainActivity.SelectItem
02-28 20:37:06.882    1107-1107/com.example.testnavigate
   E/AndroidRuntime: Uncaught handler: thread main exiting due to uncaught exception
02-28 20:37:06.882    1107-1107/com.example.testnavigate
   E/AndroidRuntime: java.lang.NoClassDefFoundError: com.example.testnavigate.MainActivity$PlanetFragment
        at com.example.testnavigate.MainActivity.SelectItem(MainActivity.java:57)
        at com.example.testnavigate.MainActivity.access$100(MainActivity.java:18)
        at com.example.testnavigate.MainActivity$ClickListener.onItemClick(MainActivity.java:52)
        at android.widget.AdapterView.performItemClick(AdapterView.java:284)
        at android.widget.ListView.performItemClick(ListView.java:3285)
        at android.widget.AbsListView$PerformClick.run(AbsListView.java:1640)
        at android.os.Handler.handleCallback(Handler.java:587)
        at android.os.Handler.dispatchMessage(Handler.java:92)
        at android.os.Looper.loop(Looper.java:123)
        at android.app.ActivityThread.main(ActivityThread.java:4363)
        at java.lang.reflect.Method.invokeNative(Native Method)
        at java.lang.reflect.Method.invoke(Method.java:521)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:860)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:618)
        at dalvik.system.NativeStart.main(Native Method)
02-28 20:37:06.892    1107-1109/com.example.testnavigate
   E/dalvikvm: Unable to open stack trace file '/data/anr/traces.txt': Permission denied
02-28 20:42:07.163        57-92/system_process
   E/gralloc: [unregister] handle 0x3f4f88 still locked (state=40000001)

如何解决此错误

---

我的应用程序在android4中运行

检查类文件是否包含在activitynot use类中。我的应用程序有一个活动。此活动的名称，MainActivitypossible的重复项