java.util.ArrayList型のオブジェクトを型モデルに変換できません

Question

FirebaseからRecycleViewにデータをロードしようとしています。しかし、私は変換エラーを取得します。

com.google.firebase.database.DatabaseException: Can't convert object of type java.util.ArrayList to type uk.co.stableweb.kithunugee.model.Hymn 
    at com.google.android.gms.internal.zzaix.zzd(Unknown Source) 
    at com.google.android.gms.internal.zzaix.zzb(Unknown Source) 
    at com.google.android.gms.internal.zzaix.zza(Unknown Source) 
    at com.google.firebase.database.DataSnapshot.getValue(Unknown Source) 
    at com.google.firebase.database.DataSnapshot.getValue(Unknown Source) 
    at com.firebase.ui.database.FirebaseRecyclerAdapter.parseSnapshot(FirebaseRecyclerAdapter.java:147) 
    at com.firebase.ui.database.FirebaseRecyclerAdapter.getItem(FirebaseRecyclerAdapter.java:136) 
    at com.firebase.ui.database.FirebaseRecyclerAdapter.onBindViewHolder(FirebaseRecyclerAdapter.java:176) 
    at android.support.v7.widget.RecyclerView$Adapter.onBindViewHolder(RecyclerView.java:5471) 
    at android.support.v7.widget.RecyclerView$Adapter.bindViewHolder(RecyclerView.java:5504) 
    at android.support.v7.widget.RecyclerView$Recycler.getViewForPosition(RecyclerView.java:4741) 
    at android.support.v7.widget.RecyclerView$Recycler.getViewForPosition(RecyclerView.java:4617) 
    at android.support.v7.widget.LinearLayoutManager$LayoutState.next(LinearLayoutManager.java:1994) 
    at android.support.v7.widget.LinearLayoutManager.layoutChunk(LinearLayoutManager.java:1390) 
    at android.support.v7.widget.LinearLayoutManager.fill(LinearLayoutManager.java:1353) 
    at android.support.v7.widget.LinearLayoutManager.onLayoutChildren(LinearLayoutManager.java:574) 
    at android.support.v7.widget.RecyclerView.dispatchLayoutStep2(RecyclerView.java:3028) 
    at android.support.v7.widget.RecyclerView.onMeasure(RecyclerView.java:2625) 
    at android.view.View.measure(View.java:18850) 
    at android.widget.RelativeLayout.measureChildHorizontal(RelativeLayout.java:716) 
    at android.widget.RelativeLayout.onMeasure(RelativeLayout.java:462) 
    at android.view.View.measure(View.java:18850) 
    at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5956) 
    at android.support.design.widget.CoordinatorLayout.onMeasureChild(CoordinatorLayout.java:668) 
    at android.support.design.widget.HeaderScrollingViewBehavior.onMeasureChild(HeaderScrollingViewBehavior.java:90) 
    at android.support.design.widget.AppBarLayout$ScrollingViewBehavior.onMeasureChild(AppBarLayout.java:1192) 
    at android.support.design.widget.CoordinatorLayout.onMeasure(CoordinatorLayout.java:733) 
    at android.view.View.measure(View.java:18850) 
    at android.support.v4.widget.DrawerLayout.onMeasure(DrawerLayout.java:1075) 
    at android.view.View.measure(View.java:18850) 
    at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5956) 
    at android.widget.FrameLayout.onMeasure(FrameLayout.java:194) 
    at android.support.v7.widget.ContentFrameLayout.onMeasure(ContentFrameLayout.java:135) 
    at android.view.View.measure(View.java:18850) 
    at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5956) 
    at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1465) 
    at android.widget.LinearLayout.measureVertical(LinearLayout.java:748) 
    at android.widget.LinearLayout.onMeasure(LinearLayout.java:630) 
    at android.view.View.measure(View.java:18850) 
    at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5956) 
    at android.widget.FrameLayout.onMeasure(FrameLayout.java:194) 
    at android.view.View.measure(View.java:18850) 
    at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5956) 
    at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1465) 
    at android.widget.LinearLayout.measureVertical(LinearLayout.java:748) 
    at android.widget.LinearLayout.onMeasure(LinearLayout.java:630) 
    at android.view.View.measure(View.java:18850) 
    at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5956) 
    at android.widget.FrameLayout.onMeasure(FrameLayout.java:194) 
    at com.android.internal.policy.PhoneWindow$DecorView.onMeasure(PhoneWindow.java:2671) 
    at android.view.View.measure(View.java:18850) 
    at android.view.ViewRootImpl.performMeasure(ViewRootImpl.java:2107) 

これは、私がRecycleViewからデータをロードする方法です。

DatabaseReference ref = FirebaseDatabase.getInstance().getReference(); 
mRecyclerViewAdapter = new FirebaseRecyclerAdapter<Hymn, HymnHolder>(Hymn.class, R.layout.hymn_row, HymnHolder.class, ref) { 
     @Override 
     protected void populateViewHolder(HymnHolder viewHolder, Hymn hymn, int position) { 
       viewHolder.setTitle(hymn.getTitle()); 
       viewHolder.setIndex(String.valueOf(hymn.getIndex())); 
     } 
}; 

// Scroll to bottom on new messages 
mRecyclerViewAdapter.registerAdapterDataObserver(new RecyclerView.AdapterDataObserver() { 
     @Override 
     public void onItemRangeInserted(int positionStart, int itemCount) { 
       mLayoutManager.smoothScrollToPosition(recyclerView, null, mRecyclerViewAdapter.getItemCount()); 
     } 
}); 

recyclerView.setAdapter(mRecyclerViewAdapter); 

そして、私のViewHolderクラスは、

public class HymnHolder extends RecyclerView.ViewHolder { 
    View mView; 

    public HymnHolder(View itemView) { 
     super(itemView); 
     mView = itemView; 
    } 

    public void setTitle(String name) { 
     TextView field = (TextView) mView.findViewById(R.id.title); 
     field.setText(name); 
    } 

    public void setIndex(String index) { 
     TextView field = (TextView) mView.findViewById(R.id.index); 
     field.setText(index); 
    } 
} 

であり、これは私のモデルです。

public class Hymn { 
    private int index; 
    private String title; 
    private String content; 

    public int getIndex() { 
     return index; 
    } 

    public void setIndex(int index) { 
     this.index = index; 
    } 

    public String getTitle() { 
     return title; 
    } 

    public void setTitle(String title) { 
     this.title = title; 
    } 

    public String getContent() { 
     return content; 
    } 

    public void setContent(String content) { 
     this.content = content; 
    } 

} 

ここに私のFirebaseデータベースの構造があります。

私はthis Firebase UIのチュートリアルを参照さ。この問題に関する以前の質問はほとんどありませんでしたが、それは私には分かりません。この問題について何かヒントがあれば、本当に役に立ちます。

Answer 1

が

古いコード

DatabaseReference ref = FirebaseDatabase.getInstance().getReference(); 

新しいコードデータベースの参照を変更し

mDatabaseReference = FirebaseDatabase.getInstance().getReference().child("geethik‌​a");