ошибка при запуске lockscreen android project

Question

Я делаю блокировку экрана Кнопка в фрагменте.
С помощью этого примера: http://karanbalkar.com/2014/01/tutorial-71-implement-lock-screen-in-android/

Мой код:

public class Tab1fragment extends Fragment implements View.OnClickListener{ 
private static final int ADMIN_INTENT = 15; 
private static final String description = "Sample Administrator description"; 
private DevicePolicyManager mDevicePolicyManager; 
private ComponentName mComponentName; 
@Override 
public View onCreateView(LayoutInflater inflater, 
     @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) { 
    // TODO Auto-generated method stub 
    //return inflater.inflate(R.layout.tab1_layout, container, false); 
    View rootView = inflater.inflate(R.layout.tab1_layout, container, false); 
    mDevicePolicyManager = (DevicePolicyManager)getActivity().getSystemService( 
      Context.DEVICE_POLICY_SERVICE); 
    mComponentName = new ComponentName(getActivity(), MyAdminReceiver.class); 
    Button btnEnableAdmin = (Button)getActivity().findViewById(R.id.btnEnable); 
    Button btnDisableAdmin = (Button)getActivity().findViewById(R.id.btnDisable); 
    Button btnLock = (Button)getActivity().findViewById(R.id.btnLock); 
    btnEnableAdmin.setOnClickListener(this); 
    btnDisableAdmin.setOnClickListener(this); 
    btnLock.setOnClickListener(this); 

    return rootView; 

} 
public static void main(String[] args) { 
    // TODO Auto-generated method stub 

} 
@Override 
public void onClick(View v) { 
    // TODO Auto-generated method stub 
    switch (v.getId()) { 
    case R.id.btnEnable: 
     Intent intent = new Intent(DevicePolicyManager.ACTION_ADD_DEVICE_ADMIN); 
     intent.putExtra(DevicePolicyManager.EXTRA_DEVICE_ADMIN, mComponentName); 
     intent.putExtra(DevicePolicyManager.EXTRA_ADD_EXPLANATION,description); 
     startActivityForResult(intent, ADMIN_INTENT); 
     break; 

    case R.id.btnDisable: 
     mDevicePolicyManager.removeActiveAdmin(mComponentName); 
     Toast.makeText(getActivity().getApplicationContext(), "Admin registration removed", Toast.LENGTH_SHORT).show(); 
     break; 

    case R.id.btnLock: 
     boolean isAdmin = mDevicePolicyManager.isAdminActive(mComponentName); 
     if (isAdmin) { 
      mDevicePolicyManager.lockNow(); 
     }else{ 
      Toast.makeText(getActivity().getApplicationContext(), "Not Registered as admin", Toast.LENGTH_SHORT).show(); 
     } 
     break; 
    } 

} 
@Override 
public void onActivityResult(int requestCode, int resultCode, Intent data) { 
    if (requestCode == ADMIN_INTENT) { 
     if (resultCode == getActivity().RESULT_OK) { 
      Toast.makeText(getActivity().getApplicationContext(), "Registered As Admin", Toast.LENGTH_SHORT).show(); 
     }else{ 
      Toast.makeText(getActivity().getApplicationContext(), "Failed to register as Admin", Toast.LENGTH_SHORT).show(); 
     } 
    } 
} 

Мои Manifest:

<application 
    android:allowBackup="true" 
    android:icon="@drawable/icon" 
    android:label="@string/app_name" 
    android:theme="@style/AppTheme" > 
    <activity 
     android:name=".MainActivity" 
     android:label="@string/app_name" > 
     <intent-filter> 
      <action android:name="android.intent.action.MAIN" /> 

      <category android:name="android.intent.category.LAUNCHER" /> 
     </intent-filter> 
    </activity> 

    <receiver android:name="MyAdminReceiver" 
     android:permission="android.permission.BIND_DEVICE_ADMIN"> 
     <meta-data 
      android:name="android.app.device_admin" 
      android:resource="@xml/admin"/> 

     <intent-filter> 
      <action android:name="android.app.action.DEVICE_ADMIN_ENABLED" /> 
     </intent-filter> 

    </receiver> 
</application> 

Но когда я начинаю это заметил ошибку:

Скажите, пожалуйста, что я сделал неправильно?

Answer 1

Я думаю, вы получаете NullPointerException, потому что btnEnableAdmin, btnDisableAdmin and btnLock - null. Попробуйте позвонить findViewById на View вы просто надуть вместо этого на активность:

@Override 
public View onCreateView(LayoutInflater inflater,@Nullable ViewGroup container, @Nullable Bundle savedInstanceState) { 
    // TODO Auto-generated method stub 
    //return inflater.inflate(R.layout.tab1_layout, container, false); 
    View rootView = inflater.inflate(R.layout.tab1_layout, container, false); 
    mDevicePolicyManager = (DevicePolicyManager)getActivity().getSystemService(Context.DEVICE_POLICY_SERVICE); 
    mComponentName = new ComponentName(getActivity(), MyAdminReceiver.class); 
    Button btnEnableAdmin = (Button) rootView.findViewById(R.id.btnEnable); 
    Button btnDisableAdmin = (Button) rootView.findViewById(R.id.btnDisable); 
    Button btnLock = (Button) rootView.findViewById(R.id.btnLock); 
    btnEnableAdmin.setOnClickListener(this); 
    btnDisableAdmin.setOnClickListener(this); 
    btnLock.setOnClickListener(this); 

    return rootView; 
}