安卓：NullPointerException异常在getActionBar

我采取抽屉式导航栏在安卓：NullPointerException异常在getActionBar

getActionBar().setDisplayShowHomeEnabled(true); 
getActionBar().setHomeButtonEnabled(true);

滑动菜单.getting java.lang.NullPointerException在我的应用我都试过活动扩展Activity也AppCompatActivity。

这里是我的onCreate代码

protected void onCreate(Bundle savedInstanceState) { 

     super.onCreate(savedInstanceState); 

     setContentView(R.layout.activity_main); 

     mTitle = mDrawerTitle = getTitle(); 

     navMenuTitles = getResources().getStringArray(R.array.nav_drawer_items); 
     navMenuIcons = getResources().obtainTypedArray(R.array.nav_drawer_icons); 
     mDrawerLayout = (DrawerLayout) findViewById(R.id.drawer_layout); 
     mDrawerList = (ListView) findViewById(R.id.list_slidermenu); 
     navDrawerItems = new ArrayList<NavDrawerItem>(); 
     navDrawerItems.add(new NavDrawerItem(navMenuTitles[0], navMenuIcons.getResourceId(0, -1))); 
     navDrawerItems.add(new NavDrawerItem(navMenuTitles[1], navMenuIcons.getResourceId(1, -1))); 
     navDrawerItems.add(new NavDrawerItem(navMenuTitles[2], navMenuIcons.getResourceId(2, -1))); 
     navDrawerItems.add(new NavDrawerItem(navMenuTitles[3], navMenuIcons.getResourceId(3, -1), true, "22")); 
     navDrawerItems.add(new NavDrawerItem(navMenuTitles[4], navMenuIcons.getResourceId(4, -1))); 
     navDrawerItems.add(new NavDrawerItem(navMenuTitles[5], navMenuIcons.getResourceId(5, -1), true, "50+")); 
     navMenuIcons.recycle(); 
     mDrawerList.setOnItemClickListener(new SlideMenuClickListener()); 
     adapter = new NavDrawerListAdapter(getApplicationContext(), navDrawerItems); 
     mDrawerList.setAdapter(adapter); 
     //abling action bar app icon and behaving it as toggle button 
     getActionBar().setDisplayShowHomeEnabled(true); 
     getActionBar().setHomeButtonEnabled(true); 
     mDrawerToggle = new ActionBarDrawerToggle(this, mDrawerLayout, 

       R.drawable.menu_left, //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); 
     } 
    }

这里是logcat的inforamtion

java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.tazeen.slidingmenu/com.example.tazeen.slidingmenu.MainActivity}: java.lang.NullPointerException 
      at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2059) 
      at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2084) 
      at android.app.ActivityThread.access$600(ActivityThread.java:130) 
      at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1195) 
      at android.os.Handler.dispatchMessage(Handler.java:99) 
      at android.os.Looper.loop(Looper.java:137) 
      at android.app.ActivityThread.main(ActivityThread.java:4745) 
      at java.lang.reflect.Method.invokeNative(Native Method) 
      at java.lang.reflect.Method.invoke(Method.java:511) 
      at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786) 
      at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553) 
      at dalvik.system.NativeStart.main(Native Method) 
    Caused by: java.lang.NullPointerException 
      at com.example.tazeen.slidingmenu.MainActivity.onCreate(MainActivity.java:62) 
      at android.app.Activity.performCreate(Activity.java:5008) 
      at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1079) 
      at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2023) 
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2084) 
            at android.app.ActivityThread.access$600(ActivityThread.java:130) 
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1195) 
            at android.os.Handler.dispatchMessage(Handler.java:99) 
            at android.os.Looper.loop(Looper.java:137) 
            at android.app.ActivityThread.main(ActivityThread.java:4745) 
            at java.lang.reflect.Method.invokeNative(Native Method) 
            at java.lang.reflect.Method.invoke(Method.java:511) 
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786) 
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553) 
            at dalvik.system.NativeStart.main(Native Method)

来源

2015-09-07 androidTag

尝试发布您的Logcat输出也。 –

[getActionBar（））可能的重复返回null]（http://stackoverflow.com/questions/6867076/getactionbar-returns-null） – alfasin

如果从AppCompatActivity你应该使用延伸getSupportActionBar()

如果要扩展形式Activity，你可以用getActionBar(),

但是在这两种情况下，

您必须确保为您的Activity分配了支持ActionBar的主题。

如：Theme.AppCompat.Light

，或者您可以通过编程做，

requestWindowFeature(Window.FEATURE_ACTION_BAR);

前

super.onCreate(savedInstanceState);

但最好是有一个风格的声明，并分配给您的活动，而不是做它以编程方式。

来源

2015-09-07 04:36:18

@androidTag你解决了这个问题吗？ –

extends简单Activity代替ActionBarActivity。而请setDisplayShowHomeEnabled()像以前那样经常检查空：

if(getActionBar()!=null){ 
    getActionBar().setDisplayShowHomeEnabled(true); 
     getActionBar().setHomeButtonEnabled(true); 
    }

，另一个解决方案是使用getSupportActionBar()代替getActionBar() 然后

if(getSupportActionBar()!=null){ 
    getSupportActionBar().setDisplayShowHomeEnabled(true); 
     getgetSupportActionBarActionBar().setHomeButtonEnabled(true); 
    }

享受你的代码:)

来源

2015-09-07 04:50:42

安卓：NullPointerException异常在getActionBar

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