"指定された子はすでにnotifyDataSetChangedの後に親を持っています"

Question

私の模擬ユーザーのセットを更新しようとしていて、それをRecyclerViewに反映させようとしています。私のFirebaseデータベースからコールバックに新しいデータを追加し、RecyclerViewのアダプタのnotifyDataSetChangedを呼び出すと、エラーThe specified child already has a parentが出ます。何か案は？

関連する私の活動ののonCreate

// Initialize Firebase and get mock users from DB 
mDatabase = FirebaseDatabase.getInstance().getReference(); 
final ArrayList<String> userNames = new ArrayList<String>(); 
DatabaseReference mockUserRef = mDatabase.child("mock_users"); 

ValueEventListener mockUserListener = new ValueEventListener() { 
    @Override 
    public void onDataChange(DataSnapshot dataSnapshot) { 
     userNames.add(dataSnapshot.getValue().toString()); 
     mRecyclerView.getAdapter().notifyDataSetChanged(); 
    } 

    @Override 
    public void onCancelled(DatabaseError databaseError) { 
     Log.w(TAG, "Mock user fetch cancelled"); 
    } 
}; 

mockUserRef.addListenerForSingleValueEvent(mockUserListener); 

// Initialize RecyclerView used to display users 
mRecyclerView = (RecyclerView) findViewById(R.id.my_recycler_view); 
mRecyclerView.setHasFixedSize(true); 

mLayoutManager = new LinearLayoutManager(this); 
mRecyclerView.setLayoutManager(mLayoutManager); 

mAdapter = new UserStackAdapter(userNames); 
mRecyclerView.setAdapter(mAdapter); 

のコードと、これは私のUserStackAdapter内の関連するコードです

private ArrayList<String> mDataset; 

static class ViewHolder extends RecyclerView.ViewHolder { 
    TextView mTextView; 

    ViewHolder(TextView v) { 
     super(v); 
     mTextView = v; 
    } 
} 

public UserStackAdapter(ArrayList<String> myDataset) { 
    mDataset = myDataset; 
} 

@Override 
public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) { 
    View v = LayoutInflater.from(parent.getContext()) 
      .inflate(R.layout.my_text_view, parent, false); 

    LinearLayout ll = (LinearLayout) v; // get the parent layout view 
    TextView tv = (TextView) ll.findViewById(R.id.item_title); // get the child text view 

    ViewHolder vh = new ViewHolder(tv); 
    return vh; 
} 

activity_main.xml

<?xml version="1.0" encoding="utf-8"?> 
<RelativeLayout 
     xmlns:android="http://schemas.android.com/apk/res/android" 
     xmlns:app="http://schemas.android.com/apk/res-auto" 
     xmlns:tools="http://schemas.android.com/tools" 
     android:id="@+id/activity_main" 
     android:layout_width="match_parent" 
     android:layout_height="match_parent" 
     android:paddingLeft="@dimen/activity_horizontal_margin" 
     android:paddingRight="@dimen/activity_horizontal_margin" 
     android:paddingTop="@dimen/activity_vertical_margin" 
     android:paddingBottom="@dimen/activity_vertical_margin" 
     tools:context="io.backlund.roomie.MainActivity"> 

    <android.support.v7.widget.Toolbar 
      android:id="@+id/my_toolbar" 
      android:layout_width="match_parent" 
      android:layout_height="?attr/actionBarSize" 
      android:background="?attr/colorPrimary" 
      android:elevation="4dp" 
      android:theme="@style/ThemeOverlay.AppCompat.ActionBar" 
      app:popupTheme="@style/ThemeOverlay.AppCompat.Light"/> 

    <android.support.v7.widget.RecyclerView 
      android:id="@+id/my_recycler_view" 
      android:scrollbars="vertical" 
      android:layout_width="match_parent" 
      android:layout_height="match_parent"/> 

</RelativeLayout> 

my_text_view.xml

<?xml version="1.0" encoding="utf-8"?> 
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" 
       android:orientation="vertical" 
       android:layout_width="match_parent" 
       android:layout_height="match_parent"> 

    <TextView 
      android:id="@+id/item_title" 
      android:layout_width="fill_parent" 
      android:layout_height="wrap_content" 
      android:textColor="@android:color/darker_gray" 
      android:layout_marginLeft="8dp" 
      android:layout_marginRight="8dp" 
      android:layout_marginTop="8dp" 
      android:textSize="22dp" /> 

</LinearLayout> 

デバッグログ

E/AndroidRuntime: FATAL EXCEPTION: main 
Process: io.backlund.roomie, PID: 11149 
java.lang.IllegalStateException: The specified child already has a parent. You must call removeView() on the child's parent first. 
    at android.view.ViewGroup.addViewInner(ViewGroup.java:4417) 
    at android.view.ViewGroup.addView(ViewGroup.java:4258) 
    at android.view.ViewGroup.addView(ViewGroup.java:4198) 
    at android.support.v7.widget.RecyclerView$5.addView(RecyclerView.java:676) 
    at android.support.v7.widget.ChildHelper.addView(ChildHelper.java:107) 
    at android.support.v7.widget.RecyclerView$LayoutManager.addViewInt(RecyclerView.java:7404) 
    at android.support.v7.widget.RecyclerView$LayoutManager.addView(RecyclerView.java:7362) 
    at android.support.v7.widget.RecyclerView$LayoutManager.addView(RecyclerView.java:7350) 
    at android.support.v7.widget.LinearLayoutManager.layoutChunk(LinearLayoutManager.java:1459) 
    at android.support.v7.widget.LinearLayoutManager.fill(LinearLayoutManager.java:1408) 
    at android.support.v7.widget.LinearLayoutManager.onLayoutChildren(LinearLayoutManager.java:580) 
    at android.support.v7.widget.RecyclerView.dispatchLayoutStep2(RecyclerView.java:3379) 
    at android.support.v7.widget.RecyclerView.dispatchLayout(RecyclerView.java:3188) 
    at android.support.v7.widget.RecyclerView.onLayout(RecyclerView.java:3632) 
    at android.view.View.layout(View.java:17637) 
    at android.view.ViewGroup.layout(ViewGroup.java:5575) 
    at android.widget.RelativeLayout.onLayout(RelativeLayout.java:1079) 
    at android.view.View.layout(View.java:17637) 
    at android.view.ViewGroup.layout(ViewGroup.java:5575) 
    at android.widget.FrameLayout.layoutChildren(FrameLayout.java:323) 
    at android.widget.FrameLayout.onLayout(FrameLayout.java:261) 
    at android.view.View.layout(View.java:17637) 
    at android.view.ViewGroup.layout(ViewGroup.java:5575) 
    at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1741) 
    at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1585) 
    at android.widget.LinearLayout.onLayout(LinearLayout.java:1494) 
    at android.view.View.layout(View.java:17637) 
    at android.view.ViewGroup.layout(ViewGroup.java:5575) 
    at android.widget.FrameLayout.layoutChildren(FrameLayout.java:323) 
    at android.widget.FrameLayout.onLayout(FrameLayout.java:261) 
    at android.view.View.layout(View.java:17637) 
    at android.view.ViewGroup.layout(ViewGroup.java:5575) 
    at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1741) 
    at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1585) 
    at android.widget.LinearLayout.onLayout(LinearLayout.java:1494) 
    at android.view.View.layout(View.java:17637) 
    at android.view.ViewGroup.layout(ViewGroup.java:5575) 
    at android.widget.FrameLayout.layoutChildren(FrameLayout.java:323) 
    at android.widget.FrameLayout.onLayout(FrameLayout.java:261) 
    at com.android.internal.policy.DecorView.onLayout(DecorView.java:726) 
    at android.view.View.layout(View.java:17637) 
    at android.view.ViewGroup.layout(ViewGroup.java:5575) 
    at android.view.ViewRootImpl.performLayout(ViewRootImpl.java:2346) 
    at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:2068) 
    at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1254) 
    at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:6337) 
    at android.view.Choreographer$CallbackRecord.run(Choreographer.java:874) 
    at android.view.Choreographer.doCallbacks(Choreographer.java:686) 
    at android.view.Choreographer.doFrame(Choreographer.java:621) 
    at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:860) 
    at android.os.Handler.handleCallback(Handler.java:751) 
    at android.os.Handler.dispatchMessage(Handler.java:95) 
    at android.os.Looper.loop(Looper.java:154) 
    at android.app.ActivityThread.main(ActivityThread.java:6119) 
    at java.lang.reflect.Method.invoke(Native Method) 
    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:886) 
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:776) 

Answer 1

私はあなたがエラーを取得している理由はわかりません。もう少し掘り下げたら答えが更新されます。私が作った

変更は

• がViewHolderにTextView初期化を移動し、あります。
• TextViewの代わりに、膨らんだビューviewが渡されました。

次のコードは、このエラーを解決します。

public class UserStackAdapter extends RecyclerView.Adapter<UserStackAdapter.ViewHolder> { 
    LayoutInflater inflater; 
    private ArrayList<String> mDataset; 

    public UserStackAdapter(ArrayList<String> myDataset) { 
     mDataset = myDataset; 
    } 

    @Override 
    public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) { 
     View v = LayoutInflater.from(parent.getContext()).inflate(R.layout.my_text_view, parent, false); 
     ViewHolder vh = new ViewHolder(v); 
     return vh; 
    } 

    @Override 
    public void onBindViewHolder(ViewHolder holder, int position) { 
     holder.mTextView.setText(mDataset.get(position)); 
    } 

    @Override 
    public int getItemCount() { 
     return mDataset.size(); 
    } 

    static class ViewHolder extends RecyclerView.ViewHolder { 
     TextView mTextView; 

     ViewHolder(View v) { 
      super(v); 
      mTextView = (TextView) v.findViewById(R.id.item_title); 
     } 
    } 
}