当我运行应用程序时，每次我在logcat中收到以下异常：

 04-14 09:29:53.965: W/dalvikvm(1020): threadid=1: thread exiting with uncaught exception (group=0x409c01f8)
    04-14 09:29:53.985: E/AndroidRuntime(1020): FATAL EXCEPTION: main
    04-14 09:29:53.985: E/AndroidRuntime(1020): java.lang.RuntimeException: Unable to instantiate application   android.app.Application: java.lang.NullPointerException
    04-14 09:29:53.985: E/AndroidRuntime(1020):     at android.app.LoadedApk.makeApplication(LoadedApk.java:482)
    04-14 09:29:53.985: E/AndroidRuntime(1020):     at android.app.ActivityThread.handleBindApplication(ActivityThread.java:3938)
    04-14 09:29:53.985: E/AndroidRuntime(1020):     at android.app.ActivityThread.access$1300(ActivityThread.java:123)
    04-14 09:29:53.985: E/AndroidRuntime(1020):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1185)
    04-14 09:29:53.985: E/AndroidRuntime(1020):     at android.os.Handler.dispatchMessage(Handler.java:99)
    04-14 09:29:53.985: E/AndroidRuntime(1020):     at android.os.Looper.loop(Looper.java:137)
    04-14 09:29:53.985: E/AndroidRuntime(1020):     at android.app.ActivityThread.main(ActivityThread.java:4424)
    04-14 09:29:53.985: E/AndroidRuntime(1020):     at java.lang.reflect.Method.invokeNative(Native Method)
    04-14 09:29:53.985: E/AndroidRuntime(1020):     at java.lang.reflect.Method.invoke(Method.java:511)
    04-14 09:29:53.985: E/AndroidRuntime(1020):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784)
    04-14 09:29:53.985: E/AndroidRuntime(1020):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551)
    04-14 09:29:53.985: E/AndroidRuntime(1020):     at dalvik.system.NativeStart.main(Native Method)
    04-14 09:29:53.985: E/AndroidRuntime(1020): Caused by: java.lang.NullPointerException
    04-14 09:29:53.985: E/AndroidRuntime(1020):     at android.app.LoadedApk.initializeJavaContextClassLoader(LoadedApk.java:362)
    04-14 09:29:53.985: E/AndroidRuntime(1020):     at android.app.LoadedApk.getClassLoader(LoadedApk.java:305)
    04-14 09:29:53.985: E/AndroidRuntime(1020):     at android.app.LoadedApk.makeApplication(LoadedApk.java:474)
    04-14 09:29:53.985: E/AndroidRuntime(1020):     ... 11 more

注意：当我从仿真器中卸载应用程序并运行它时，我没有收到此异常，但是当我在仿真器中重新运行已安装的应用程序时，却收到了此异常。请帮忙。