Question

04-03 10:19:34.572    2189-2189/com.techexpert4u.duaaadhkaar E/AndroidRuntime﹕ FATAL EXCEPTION: main
    Process: com.techexpert4u.duaaadhkaar, PID: 2189
    java.lang.RuntimeException: Unable to start activity ComponentInfo{com.techexpert4u.duaaadhkaar/com.techexpert4u.duaaadhkaar.MainActivity}: java.lang.NullPointerException
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2195)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2245)
            at android.app.ActivityThread.access$800(ActivityThread.java:135)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196)
            at android.os.Handler.dispatchMessage(Handler.java:102)
            at android.os.Looper.loop(Looper.java:136)
            at android.app.ActivityThread.main(ActivityThread.java:5017)
            at java.lang.reflect.Method.invokeNative(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:515)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
            at dalvik.system.NativeStart.main(Native Method)
     Caused by: java.lang.NullPointerException
            at com.techexpert4u.duaaadhkaar.MainActivity.onPostCreate(MainActivity.java:936)
            at android.app.Instrumentation.callActivityOnPostCreate(Instrumentation.java:1150)
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2178)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2245)
            at android.app.ActivityThread.access$800(ActivityThread.java:135)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196)
            at android.os.Handler.dispatchMessage(Handler.java:102)
            at android.os.Looper.loop(Looper.java:136)
            at android.app.ActivityThread.main(ActivityThread.java:5017)
            at java.lang.reflect.Method.invokeNative(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:515)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
            at dalvik.system.NativeStart.main(Native Method)

我需要帮助，请帮助我。

@Override
protected void onPostCreate(Bundle savedInstanceState) {
    super.onPostCreate(savedInstanceState);
    // Sync the toggle state after onRestoreInstanceState has occurred.
    mDrawerToggle.syncState();
}

Answer 1

鉴于源和堆栈跟踪，显然mDrawerToggle为null。

Answer 2

null mDrawerToggle字段似乎应该在您的initializeDrawer（）代码中初始化，但没有证据表明您曾调用该方法。

在onCreate（）中调用initializeDrawer，或者在尝试使用mDrawerToggle 之前确保它在任何代码路径中发生。

引起：java.lang.NullPointerException MainActivity.onPostCreate

2 个答案: