Question

好的，首先，我知道什么是NullPointer，但想问一下可能导致这种行为的原因。我在Crittercism收到了崩溃，stacktrace指向List.add：

java.lang.NullPointerException: Attempt to invoke interface method 'boolean java.util.List.add(java.lang.Object)' on a null object reference
at com.xxx.android.activities.SuperActivity.onCreate(SourceFile:59)
at com.xxx.android.activities.XXXActivity.onCreate(SourceFile:30)

但事实是onCreate甚至整个SuperActivity都没有列表。什么可能导致stacktrace中出现Android这样的问题？如何找到此NullPointer或类似来源？

修改根据第59行的要求SuperActivity代码：

super.onCreate(savedInstanceState);

    if (activitiesCreated == 0) {
        isFirstStart = true;
    }
    activitiesCreated++;

编辑2 我知道如何关注stacktrace。我想知道的是什么可能是问题，在这样的情况下我该怎么办？

编辑3 崩溃线程的Stacktrace：

java.lang.RuntimeException: Unable to start activity ComponentInfo{com.xxx.android/com.xxx.android.activities.XXXActivity}: java.lang.NullPointerException: Attempt to invoke interface method 'boolean java.util.List.add(java.lang.Object)' on a null object reference    
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2416)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2476)
at android.app.ActivityThread.-wrap11(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1344)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:148)
at android.app.ActivityThread.main(ActivityThread.java:5417)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
Caused by: java.lang.NullPointerException: Attempt to invoke interface method 'boolean java.util.List.add(java.lang.Object)' on a null object reference
at com.xxx.android.activities.SuperActivity.onCreate(SourceFile:59)
at com.xxx.android.activities.XXXActivity.onCreate(SourceFile:30)
at android.app.Activity.performCreate(Activity.java:6237)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1107)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2369)
... 9 more
java.lang.NullPointerException: Attempt to invoke interface method 'boolean java.util.List.add(java.lang.Object)' on a null object reference
at com.xxx.android.activities.SuperActivity.onCreate(SourceFile:59) 
at com.xxx.android.activities.XXXActivity.onCreate(SourceFile:30)   
at android.app.Activity.performCreate(Activity.java:6237)   
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1107)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2369)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2476)
at android.app.ActivityThread.-wrap11(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1344)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:148)  
at android.app.ActivityThread.main(ActivityThread.java:5417)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)

不典型的NullPointer异常

0 个答案: