Fragment "+ this +"not attached to Activity 예외 해결

문제가 발생했습니다. 새로운 페이지 (Fragment) 를 시작하면 네트워크가 시간을 소모하고, Fragment를 호출하는 getstring () 방법으로 UI를 업데이트합니다. 그러나 네트워크가 아직 완성되지 않았다면, 우리는 즉시 페이지를 닫습니다. 이 오류를 보고합니다.코드는 다음과 같습니다.

public class TestFragment extends Fragment {
    // TODO: Rename parameter arguments, choose names that match
    // the fragment initialization parameters, e.g. ARG_ITEM_NUMBER
    private static final String ARG_PARAM1 = "param1";
    private static final String ARG_PARAM2 = "param2";

    // TODO: Rename and change types of parameters
    private String mParam1;
    private String mParam2;

    private OnFragmentInteractionListener mListener;

    private TextView textView ;

    private Handler handler = new Handler()
    {
        @Override
        public void handleMessage(Message msg) {
            super.handleMessage(msg);
            textView.setText(getString(R.string.app_name));
        }
    };

    /**
     * Use this factory method to create a new instance of
     * this fragment using the provided parameters.
     *
     * @param param1 Parameter 1.
     * @param param2 Parameter 2.
     * @return A new instance of fragment TestFragment.
     */
    // TODO: Rename and change types and number of parameters
    public static TestFragment newInstance(String param1, String param2) {
        TestFragment fragment = new TestFragment();
        Bundle args = new Bundle();
        args.putString(ARG_PARAM1, param1);
        args.putString(ARG_PARAM2, param2);
        fragment.setArguments(args);
        return fragment;
    }

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        if (getArguments() != null) {
            mParam1 = getArguments().getString(ARG_PARAM1);
            mParam2 = getArguments().getString(ARG_PARAM2);
        }
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        // Inflate the layout for this fragment
        View view =  inflater.inflate(R.layout.fragment_test, container, false);
        textView = (TextView)view.findViewById(R.id.test);
        //        
        new Thread(new Runnable() {
            @Override
            public void run() {
               try {
                    Thread.sleep(4000);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
                handler.sendEmptyMessage(1);
            }
        }).start();
        return view;
    }

    // TODO: Rename method, update argument and hook method into UI event

    @Override
    public void onAttach(Context context) {
        super.onAttach(context);
    }

    @Override
    public void onDetach() {
        super.onDetach();
        mListener = null;
    }

    @Override
    public void onDestroyView() {
        super.onDestroyView();
       // handler.removeCallbacksAndMessages(null);
       /* handler.removeMessages(1);
        handler.re*/
    }

    @Override
    public void onDestroy() {
        super.onDestroy();
        handler.removeCallbacksAndMessages(null);
    }

    /**
     * This interface must be implemented by activities that contain this
     * fragment to allow an interaction in this fragment to be communicated
     * to the activity and potentially other fragments contained in that
     * activity.
     * 

     * See the Android Training lesson Communicating with Other Fragments for more information.
     */
    public interface OnFragmentInteractionListener {
        // TODO: Update argument type and name
        void onFragmentInteraction(Uri uri);
    }
}

이 인터페이스에 들어가면 우리는 단지 네트워크가 시간을 소모하는 조작을 한 후에 메시지를 보내서 메인 인터페이스를 업데이트할 뿐인데 왜 붕괴되었을까?Google은 getString () 의 원본 코드를 보았습니다.

public final String getString(@StringRes int resId) {
        return getResources().getString(resId);
    }

getResources () 가 호출되고 아래를 봅니다.

final public Resources getResources() {
        if (mHost == null) {
            throw new IllegalStateException("Fragment " + this + " not attached to Activity");
        }
        return mHost.getContext().getResources();
    }

mHost==null, 이 이상을 보고합니다. 인터페이스가 소각되면 mHost는null로 설정됩니다.그럼 이 문제를 어떻게 해결합니까?소스를 보면 다음과 같습니다.

 /**
     * Return true if the fragment is currently added to its activity.
     */
    final public boolean isAdded() {
        return mHost != null && mAdded;
    }

이 방법은 mHost가 비어 있는지 판단하기 때문에 저희가 네트워크에서 요청을 한 후에 UI를 조작하기 전에 이 말을 덧붙여서 판단을 해서 붕괴 문제를 해결할 수 있습니다!

public class TestFragment extends Fragment {
    // TODO: Rename parameter arguments, choose names that match
    // the fragment initialization parameters, e.g. ARG_ITEM_NUMBER
    private static final String ARG_PARAM1 = "param1";
    private static final String ARG_PARAM2 = "param2";

    // TODO: Rename and change types of parameters
    private String mParam1;
    private String mParam2;

    private OnFragmentInteractionListener mListener;

    private TextView textView ;

    private Handler handler = new Handler()
    {
        @Override
        public void handleMessage(Message msg) {
            super.handleMessage(msg);
            if(isAdded())//          
            textView.setText(getString(R.string.app_name));
        }
    };

    /**
     * Use this factory method to create a new instance of
     * this fragment using the provided parameters.
     *
     * @param param1 Parameter 1.
     * @param param2 Parameter 2.
     * @return A new instance of fragment TestFragment.
     */
    // TODO: Rename and change types and number of parameters
    public static TestFragment newInstance(String param1, String param2) {
        TestFragment fragment = new TestFragment();
        Bundle args = new Bundle();
        args.putString(ARG_PARAM1, param1);
        args.putString(ARG_PARAM2, param2);
        fragment.setArguments(args);
        return fragment;
    }

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        if (getArguments() != null) {
            mParam1 = getArguments().getString(ARG_PARAM1);
            mParam2 = getArguments().getString(ARG_PARAM2);
        }
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        // Inflate the layout for this fragment
        View view =  inflater.inflate(R.layout.fragment_test, container, false);
        textView = (TextView)view.findViewById(R.id.test);
        //        
        new Thread(new Runnable() {
            @Override
            public void run() {
               try {
                    Thread.sleep(4000);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
               handler.sendEmptyMessage(1);
            }
        }).start();
        return view;
    }

    // TODO: Rename method, update argument and hook method into UI event

    @Override
    public void onAttach(Context context) {
        super.onAttach(context);
    }

    @Override
    public void onDetach() {
        super.onDetach();
        mListener = null;
    }

    @Override
    public void onDestroyView() {
        super.onDestroyView();
       // handler.removeCallbacksAndMessages(null);
       /* handler.removeMessages(1);
        handler.re*/
    }

    @Override
    public void onDestroy() {
        super.onDestroy();
        handler.removeCallbacksAndMessages(null);
    }

    /**
     * This interface must be implemented by activities that contain this
     * fragment to allow an interaction in this fragment to be communicated
     * to the activity and potentially other fragments contained in that
     * activity.
     * 

     * See the Android Training lesson Communicating with Other Fragments for more information.
     */
    public interface OnFragmentInteractionListener {
        // TODO: Update argument type and name
        void onFragmentInteraction(Uri uri);
    }
}

OK, 문제 해결.