android - fragment 加载后删除 Activity View

Question

我有一个托管 fragment 的 Activity 。除了指示 fragment 正在加载的微调器外，该 Activity 基本上没有任何内容。该 fragment 依赖于稳定的互联网连接，因此微调器可见所需的时间长度本质上是动态的。

我想在 fragment 成功加载后删除 Activity 上的微调器。我尝试使用 isAdded() 方法，但该方法不起作用。任何帮助表示赞赏:

fragment :

public class LatestFragment 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";

private RecyclerView mRecyclerViewForLatestPolls;
private RecyclerView.Adapter mLatestAdapter;

private ArrayList<LatestPoll> mLatestPollsArray;

private DateFormat mDateFormat;
private Date mDate;
private String mCurrentDateString;

private Firebase mBaseRef;
private Firebase mPollRef;
private Firebase mUpdateRef;

private FragmentListener mFragmentListener;

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


private OnFragmentInteractionListener mListener;

public LatestFragment() {
    // Required empty public constructor
}

/**
 * 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 LatestFragment.
 */
// TODO: Rename and change types and number of parameters
public static LatestFragment newInstance(String param1, String param2) {
    LatestFragment fragment = new LatestFragment();
    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);
    mDateFormat = new SimpleDateFormat("MM-dd-yyyy");
    mDate = new Date();
    mCurrentDateString = mDateFormat.format(mDate);
    mBaseRef = FirebaseUtil.FIREBASE;
    mPollRef = mBaseRef.child("Polls");
    mUpdateRef = mPollRef.child(mCurrentDateString);


}

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

    final ViewGroup rootView = (ViewGroup) inflater.inflate(R.layout.fragment_latest, container, false);
    getActivity().setTitle(R.string.latest_title);

    mRecyclerViewForLatestPolls = (RecyclerView) rootView.findViewById(R.id.latest_RecyclerView);
    mLatestPollsArray = new ArrayList<>();
    mLatestAdapter = new MyAdapter(mLatestPollsArray);
    LinearLayoutManager llm = new LinearLayoutManager(getActivity().getApplicationContext());
    llm.setOrientation(LinearLayoutManager.VERTICAL);
    mRecyclerViewForLatestPolls.setLayoutManager(llm);
    mRecyclerViewForLatestPolls.setItemAnimator(new SlideInLeftAnimator());
    mRecyclerViewForLatestPolls.setAdapter(new AlphaInAnimationAdapter(mLatestAdapter));

    mUpdateRef.addListenerForSingleValueEvent(new ValueEventListener() {
        @Override
        public void onDataChange(DataSnapshot dataSnapshot) {
            int numberOfPollsForDay = (int) dataSnapshot.getChildrenCount();
            for (int i = 0; i < numberOfPollsForDay; i++) {
                String latestPollQuestion = (String) dataSnapshot.child(String.valueOf(i + 1)).child("Poll_Question").getValue();
                String pollImageURL = (String) dataSnapshot.child(String.valueOf(i + 1)).child("Image").getValue();
                mLatestPollsArray.add(0, new LatestPoll(latestPollQuestion, pollImageURL));
                mLatestAdapter.notifyDataSetChanged();
            }
        }

        @Override
        public void onCancelled(FirebaseError firebaseError) {

        }
    });


    // Inflate the layout for this fragment
    return rootView;
}


// TODO: Rename method, update argument and hook method into UI event
public void onButtonPressed(Uri uri) {
    if (mListener != null) {
        mListener.onFragmentInteraction(uri);
    }
}

@Override
public void onAttach(Context context) {
    super.onAttach(context);
    if (context instanceof OnFragmentInteractionListener) {
        mListener = (OnFragmentInteractionListener) context;
    } else {
        throw new RuntimeException(context.toString()
                + " must implement OnFragmentInteractionListener");
    }

    // Force the parent activity to implement listener.
    if (context instanceof FragmentListener) {
        mFragmentListener = (FragmentListener) context;
    } else {
        throw new RuntimeException(context.toString()
                + " must implement OnFragmentInteractionListener");
    }
}

@Override
public void onDetach() {
    super.onDetach();
    mListener = null;
    mFragmentListener = 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.
 * <p/>
 * See the Android Training lesson <a href=
 * "http://developer.android.com/training/basics/fragments/communicating.html"
 * >Communicating with Other Fragments</a> for more information.
 */
public interface OnFragmentInteractionListener {
    // TODO: Update argument type and name
    void onFragmentInteraction(Uri uri);
}

public class MyAdapter extends RecyclerView.Adapter<MyAdapter.ViewHolder> {


    private ArrayList<LatestPoll> mDataSet;
    int lastPosition = -1;


    // Provide a reference to the views for each data item
    // Complex data items may need more than one view per item, and
    // you provide access to all the views for a data item in a view holder
    public class ViewHolder extends RecyclerView.ViewHolder {
        // each data item is just a string in this case
        protected TextView pollQuestion;
        protected ImageView pollImage;


        public ViewHolder(View v) {
            super(v);
            pollQuestion = (TextView) v.findViewById(R.id.latest_item_question);
            pollImage = (ImageView) v.findViewById(R.id.pollThumbNailImage);


        }
    }

    // Provide a suitable constructor (depends on the kind of dataset)
    public MyAdapter(ArrayList<LatestPoll> myDataset) {
        mDataSet = myDataset;
    }

    // Create new views (invoked by the layout manager)
    @Override
    public ViewHolder onCreateViewHolder(ViewGroup parent,
                                         int viewType) {
        // create a new view
        View v = LayoutInflater.from(parent.getContext())
                .inflate(R.layout.latest_item, parent, false);
        // set the view's size, margins, paddings and layout parameters
        return new ViewHolder(v);
    }

    // Replace the contents of a view (invoked by the layout manager)

    //The OutOfBoundsException is pointing here
    @Override
    public void onBindViewHolder(ViewHolder holder, int position) {
        Log.v("ON_BIND", "ON_BINDVIEWHOLDER CALLED");
        LatestPoll latestPoll = mDataSet.get(position);
        holder.pollQuestion.setText(latestPoll.getQuestion());
        Picasso.with(getActivity())
                .load(latestPoll.getPollImage())
                .fit()
                .placeholder(R.drawable.loading_spinnter_white)
                .into(holder.pollImage);
    }




    // Return the size of your dataset (invoked by the layout manager)
    @Override
    public int getItemCount() {
        return mDataSet.size();
    }
}

private void onLoad() {
    if (mFragmentListener != null) {
        mFragmentListener.onFragmentLoaded();
    }
}

public interface FragmentListener {
    void onFragmentLoaded();
}


}

Activity XML:

<?xml version="1.0" encoding="utf-8"?>
<android.support.v4.widget.DrawerLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/drawer_layout"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical">

<LinearLayout
    android:id="@+id/content_frame"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="@color/black"
    android:orientation="vertical">

    <android.support.v7.widget.Toolbar
        android:id="@+id/action_tool_bar"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:background="@color/black"
        android:titleTextColor="@color/white">

    </android.support.v7.widget.Toolbar>

    <FrameLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent">

        <RelativeLayout
            android:layout_width="match_parent"
            android:layout_height="match_parent">

            <ProgressBar
                android:id="@+id/pbHeaderProgress"
                android:layout_width="150dp"
                android:layout_height="150dp"
                android:layout_centerInParent="true"
                android:progressDrawable="@drawable/loading_spinnter_white">
            </ProgressBar>

            <TextView
                android:id="@+id/progress_text"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_below="@+id/pbHeaderProgress"
                android:layout_centerHorizontal="true"
                android:layout_gravity="center_horizontal"
                android:gravity="center"
                android:text="@string/loading_poll_data"
                android:textColor="@color/white"
                android:textSize="24sp" />
        </RelativeLayout>

        <FrameLayout
            android:id="@+id/latest_fragment_container"
            android:layout_width="match_parent"
            android:layout_height="match_parent">
        </FrameLayout>
    </FrameLayout>
</LinearLayout>

<!-- The navigation drawer -->
<ListView
    android:id="@+id/left_drawer"
    android:layout_width="240dp"
    android:layout_height="match_parent"
    android:layout_gravity="start"
    android:background="#111"
    android:choiceMode="singleChoice"
    android:divider="@android:color/transparent"
    android:dividerHeight="0dp" />

图片:

Answer 1

在 fragment 中创建一个监听器接口(interface)，

private MyFragmentListener mListener;

/**
* onLoad should be called when the fragment has loaded.
*/
private void onLoad() {
    if (mListener != null) {
        mListener.onFragmentLoaded();
    }
}

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

    // Force the parent activity to implement listener.
    if (context instanceof MyFragmentListener) {
        mListener = (MyFragmentListener) context;
    } else {
        throw new RuntimeException(context.toString()
                + " must implement OnFragmentInteractionListener");
    }
}

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


public interface MyFragmentListener {
    void onFragmentLoaded();
}

然后在父 Activity 中，

public class MainActivity extends Activity implements MyFragment.MyFragmentListener{

@Override
public void onFragmentLoad() {
    // HIDE the progressbar spinner.
}

参见 Communicating with Other Fragments了解更多信息。