片段中的空指針異常

Question

片段中的空指針異常。我試圖獲得座標，並把它放到TextView中。 GPS工作正常。但不能設置文本。什麼問題可以在這裏？可能是我必須使用適配器？我能做什麼？

tv.setText(g); // error (is null) 




public class TwoFragment extends Fragment { 
LocationService ls; 
double s; 
TextView tv; 
String g; 

@Override 
public View onCreateView(LayoutInflater inflater, ViewGroup container, 
         Bundle savedInstanceState) { 

    // Creating view correspoding to the fragment 
    View v = inflater.inflate(R.layout.two_fragment, container, false); 

    // Updating the action bar title 
    getActivity().getActionBar(); 
    Log.w("MY_TAG", "One fragment"); 

    return v; 

} 

@Override 
public void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 

    ls = new LocationService(getActivity()); 
    s = ls.getLocation().getLatitude(); 
    tv = (TextView) getView().findViewById(R.id.tv_two_fragment); 
    g = Double.toString(s); 
    tv.setText(g); 
} 

}

錯誤日誌

05-19 10:36:01.052 2418-2418/com.example.projectx E/AndroidRuntime﹕ FATAL EXCEPTION: main 
java.lang.NullPointerException 
     at com.fotoman.prox.app.MainFragments.TwoFragment.onCreate(TwoFragment.java:48) 
     at android.app.Fragment.performCreate(Fragment.java:1673) 
     at android.app.FragmentManagerImpl.moveToState(FragmentManager.java:854) 
     at android.app.FragmentManagerImpl.moveToState(FragmentManager.java:1057) 
     at android.app.BackStackRecord.run(BackStackRecord.java:682) 
     at android.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1435) 
     at android.app.FragmentManagerImpl$1.run(FragmentManager.java:441) 
     at android.os.Handler.handleCallback(Handler.java:730) 
     at android.os.Handler.dispatchMessage(Handler.java:92) 
     at android.os.Looper.loop(Looper.java:137) 
     at android.app.ActivityThread.main(ActivityThread.java:5103) 
     at java.lang.reflect.Method.invokeNative(Native Method) 
     at java.lang.reflect.Method.invoke(Method.java:525) 
     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:737) 
     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553) 
     at dalvik.system.NativeStart.main(Native Method) 

Answer 1

在片段的onCreateView初始化TextView的。

View v = inflater.inflate(R.layout.two_fragment, container, false); 
tv = (TextView) v.findViewById(R.id.tv_two_fragment); 
ls = new LocationService(getActivity()); 
s = ls.getLocation().getLatitude(); 
g = Double.toString(s); 
tv.setText(g); 

getView()返回null。

http://developer.android.com/reference/android/app/Fragment.html#getView()