关于应用程序启动时，提示空指针问题

最近在开发程序时，logcat偶尔会打印如下错误信息，但是程序却可以正常运行： 

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

    在网上搜了一下，也有不少人遇到这个问题，但是绝大多数都没有给出原因和解决方案，都是一些猜想~后来在国外的论坛上，看到一个回帖，觉得有些靠谱：

   

55down voteaccepted

This is a verbose error message raised by underlying framework when dalvik re-install .apk file and trying to reuse or recycle the previous opened activity/view from the same package (if you haven't closed the previous installed app yet). It has nothing to do with your app, moreover, it is very unlikely that your app will get freezed or crashed cause by this verbose error message on end user's device.

It seems that this dalvik verbose error log only happend on Android 4.0 system, I've tested it myself on Android 3.2 and 2.3.3 running environment, where you cannot replicate to get this message shown on neither of them. A similar question has been discussed before at here and someone has filled a bug report in Android Issues Tracker.

I don't think you should concern too much about this verbose error log at the moment, if you look more logs before and after this red error in Logcat, you can see the full story and find that the previous opened activity/view (which are marked as died state) get killed and the newly re-installed one get poped ultimately.

仅供大家参考~