java.lang.NullPointerException試圖啓用動作欄應用程序圖標，並將其作爲切換按鈕

Question

這一件事是讓我回來..應用程序崩潰，只要它啓動，logcat指向以下引起的問題（2nd線下）：

// enabling action bar app icon and behaving it as toggle button 
      getActionBar().setDisplayHomeAsUpEnabled(true); 
      getActionBar().setHomeButtonEnabled(true); 

mDrawerToggle = new ActionBarDrawerToggle(this, mDrawerLayout, 
       R.drawable.ic_drawer, //nav menu toggle icon 
       R.string.app_name, // nav drawer open - description for accessibility 
       R.string.app_name // nav drawer close - description for accessibility 
     ) { 
      public void onDrawerClosed(View view) { 
       getActionBar().setTitle(mTitle); 
       // calling onPrepareOptionsMenu() to show action bar icons 
       invalidateOptionsMenu(); 
      } 

      public void onDrawerOpened(View drawerView) { 
       getActionBar().setTitle(mDrawerTitle); 
       // calling onPrepareOptionsMenu() to hide action bar icons 
       invalidateOptionsMenu(); 
      } 
     }; 
     mDrawerLayout.setDrawerListener(mDrawerToggle); 

     if (savedInstanceState == null) { 
      // on first time display view for first nav item 
      displayView(0); 
     } 
    } 

的logcat：

12-11 01:25:51.852 10780-10780/com.example.paul.amityhealth W/dalvikvm﹕ threadid=1: thread exiting with uncaught exception (group=0x41979c98) 
12-11 01:25:51.852 10780-10780/com.example.paul.amityhealth W/dalvikvm﹕ threadid=1: uncaught exception occurred 
12-11 01:25:51.853 10780-10780/com.example.paul.amityhealth W/System.err﹕ java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.paul.amityhealth/com.example.paul.amityhealth.MainActivity}: java.lang.NullPointerException 
12-11 01:25:51.855 10780-10780/com.example.paul.amityhealth W/System.err﹕ at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2358) 
12-11 01:25:51.856 10780-10780/com.example.paul.amityhealth W/System.err﹕ at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2410) 
12-11 01:25:51.857 10780-10780/com.example.paul.amityhealth W/System.err﹕ at android.app.ActivityThread.access$800(ActivityThread.java:155) 
12-11 01:25:51.858 10780-10780/com.example.paul.amityhealth W/System.err﹕ at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1331) 
12-11 01:25:51.859 10780-10780/com.example.paul.amityhealth W/System.err﹕ at android.os.Handler.dispatchMessage(Handler.java:110) 
12-11 01:25:51.860 10780-10780/com.example.paul.amityhealth W/System.err﹕ at android.os.Looper.loop(Looper.java:193) 
12-11 01:25:51.860 10780-10780/com.example.paul.amityhealth W/System.err﹕ at android.app.ActivityThread.main(ActivityThread.java:5388) 
12-11 01:25:51.861 10780-10780/com.example.paul.amityhealth W/System.err﹕ at java.lang.reflect.Method.invokeNative(Native Method) 
12-11 01:25:51.862 10780-10780/com.example.paul.amityhealth W/System.err﹕ at java.lang.reflect.Method.invoke(Method.java:515) 
12-11 01:25:51.863 10780-10780/com.example.paul.amityhealth W/System.err﹕ at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839) 
12-11 01:25:51.863 10780-10780/com.example.paul.amityhealth W/System.err﹕ at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:655) 
12-11 01:25:51.865 10780-10780/com.example.paul.amityhealth W/System.err﹕ at dalvik.system.NativeStart.main(Native Method) 
12-11 01:25:51.866 10780-10780/com.example.paul.amityhealth W/System.err﹕ Caused by: java.lang.NullPointerException 
12-11 01:25:51.868 10780-10780/com.example.paul.amityhealth W/System.err﹕ at com.example.paul.amityhealth.MainActivity.onCreate(MainActivity.java:86) 
12-11 01:25:51.869 10780-10780/com.example.paul.amityhealth W/System.err﹕ at android.app.Activity.performCreate(Activity.java:5280) 
12-11 01:25:51.870 10780-10780/com.example.paul.amityhealth W/System.err﹕ at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1088) 
12-11 01:25:51.871 10780-10780/com.example.paul.amityhealth W/System.err﹕ at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2322) 
12-11 01:25:51.872 10780-10780/com.example.paul.amityhealth W/System.err﹕ ... 11 more 
12-11 01:25:51.872 10780-10780/com.example.paul.amityhealth W/dalvikvm﹕ threadid=1: calling UncaughtExceptionHandler 
12-11 01:25:51.884 10780-10780/com.example.paul.amityhealth E/AndroidRuntime﹕ FATAL EXCEPTION: main 
    Process: com.example.paul.amityhealth, PID: 10780 
    java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.paul.amityhealth/com.example.paul.amityhealth.MainActivity}: java.lang.NullPointerException 
      at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2358) 
      at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2410) 
      at android.app.ActivityThread.access$800(ActivityThread.java:155) 
      at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1331) 
      at android.os.Handler.dispatchMessage(Handler.java:110) 
      at android.os.Looper.loop(Looper.java:193) 
      at android.app.ActivityThread.main(ActivityThread.java:5388) 
      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:839) 
      at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:655) 
      at dalvik.system.NativeStart.main(Native Method) 
    Caused by: java.lang.NullPointerException 
      at com.example.paul.amityhealth.MainActivity.onCreate(MainActivity.java:86) 
      at android.app.Activity.performCreate(Activity.java:5280) 
      at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1088) 
      at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2322) 
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2410) 
            at android.app.ActivityThread.access$800(ActivityThread.java:155) 
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1331) 
            at android.os.Handler.dispatchMessage(Handler.java:110) 
            at android.os.Looper.loop(Looper.java:193) 
            at android.app.ActivityThread.main(ActivityThread.java:5388) 
            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:839) 
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:655) 
            at dalvik.system.NativeStart.main(Native Method) 

我試圖改變爲假，不工作要麼。即使消除這兩條線也沒有幫助，我找不到答案。我是一個相對較新的開發人員，所以如果你的回答簡單易懂，歡呼！

編輯：添加斷點後，該顯示：

this = {com.example.paul.amityhealth.MainActivity@830043175400} 
savedInstanceState = null 
mDrawerList = {android.widget.ListView@830043260048}"android.widget.ListView{426f0490 VFED.VC. ......I. 0,0-0,0 #7f090041 app:id/list_slidermenu}" 
adapter = {com.example.paul.amityhealth.NavDrawerListAdapter@830043274344} 
mDrawerToggle = null 

解決：

我增加了以下內容清單文件：

android:theme="@android:style/Theme.Holo.Light" 

感謝您的支持！

Answer 1

也許這是bug，也許不是，但是我的朋友在他幾天前開始與Android開發他的冒險時遇到了同樣的問題。 com.example是原因

更改您的軟件包，重建和清理項目。如果這沒有幫助，請創建一個新的項目，而不要以包名稱開頭。

並檢查您的res/values/styles.xml文件，也許你禁用它的操作欄。 應該是

<item name="android:windowActionBar">true</item> 
<item name="windowActionBar">true</item>