隐藏片段中的操作栏会抛出NullPointerException吗？

Question

我正在尝试隐藏片段中的动作栏.要做到这一点我正在尝试使用getActivity().getActionBar().hide();,但确实会抛出异常NullPointerException.我确实尝试过使用getSupportActionBar()但Eclipse不显示自动完成功能,只显示它getActionBar();

我该怎么做 ？

分段

public class MyFragment extends Fragment {
@Override
        public void onCreate(Bundle savedInstanceState) {           
            super.onCreate(savedInstanceState); 
            getActivity().getActionBar().hide();  //nullpointerexception in this line       
        }  
}

例外:

12-05 12:19:02.415: E/AndroidRuntime(16400): FATAL EXCEPTION: main
12-05 12:19:02.415: E/AndroidRuntime(16400): java.lang.NullPointerException
12-05 12:19:02.415: E/AndroidRuntime(16400):    at br.com.mypackage.myapp.frags.BatalhaSemOponenteFrag.onCreate(BatalhaSemOponenteFrag.java:71)
12-05 12:19:02.415: E/AndroidRuntime(16400):    at android.support.v4.app.Fragment.performCreate(Fragment.java:1763)
12-05 12:19:02.415: E/AndroidRuntime(16400):    at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:913)
12-05 12:19:02.415: E/AndroidRuntime(16400):    at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1126)
12-05 12:19:02.415: E/AndroidRuntime(16400):    at android.support.v4.app.BackStackRecord.run(BackStackRecord.java:739)
12-05 12:19:02.415: E/AndroidRuntime(16400):    at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1489)
12-05 12:19:02.415: E/AndroidRuntime(16400):    at android.support.v4.app.FragmentManagerImpl$1.run(FragmentManager.java:454)
12-05 12:19:02.415: E/AndroidRuntime(16400):    at android.os.Handler.handleCallback(Handler.java:730)
12-05 12:19:02.415: E/AndroidRuntime(16400):    at android.os.Handler.dispatchMessage(Handler.java:92)
12-05 12:19:02.415: E/AndroidRuntime(16400):    at android.os.Looper.loop(Looper.java:176)
12-05 12:19:02.415: E/AndroidRuntime(16400):    at android.app.ActivityThread.main(ActivityThread.java:5419)
12-05 12:19:02.415: E/AndroidRuntime(16400):    at java.lang.reflect.Method.invokeNative(Native Method)
12-05 12:19:02.415: E/AndroidRuntime(16400):    at java.lang.reflect.Method.invoke(Method.java:525)
12-05 12:19:02.415: E/AndroidRuntime(16400):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1046)
12-05 12:19:02.415: E/AndroidRuntime(16400):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:862)
12-05 12:19:02.415: E/AndroidRuntime(16400):    at dalvik.system.NativeStart.main(Native Method)

Answer 1

由于您使用的是v4支持片段,我假设您将使用appcompat进行活动.
您必须将从getActivity()获得的活动转换为实际活动,以便将活动识别为appcompat.

试试这个:

public class MyFragment extends Fragment {
@Override
    public void onCreate(Bundle savedInstanceState) {           
        super.onCreate(savedInstanceState); 
((YourActivity)getActivity()).getSupportActionBar().hide();
    }  
}