Firebase 回收器视图仅在第三个孩子上显示错误

Question

我正在制作一个基于 firebase 实时数据库的 android 应用程序。我正在尝试在回收站视图中获取我的数据。

这是数据库结构：

我可以在我的回收站视图中显示“Unseen”和“0”。但我实际上在我的回收站视图中需要“eeee”并收到以下错误：

2020-12-16 00:44:14.002 30685-30685 E/Toast: setGravity() shouldn't be called on text toasts, the values won't be used
2020-12-16 00:44:17.897 30685-30685 E/AndroidRuntime: FATAL EXCEPTION: main
    Process: com.my app name, PID: 30685
    com.google.firebase.database.DatabaseException: Can't convert object of type java.util.ArrayList to type com.my app name.model.model
        at com.google.firebase.database.core.utilities.encoding.CustomClassMapper.convertBean(CustomClassMapper.java:436)
        at com.google.firebase.database.core.utilities.encoding.CustomClassMapper.deserializeToClass(CustomClassMapper.java:232)
        at com.google.firebase.database.core.utilities.encoding.CustomClassMapper.convertToCustomClass(CustomClassMapper.java:80)
        at com.google.firebase.database.DataSnapshot.getValue(DataSnapshot.java:203)
        at com.firebase.ui.database.ClassSnapshotParser.parseSnapshot(ClassSnapshotParser.java:29)
        at com.firebase.ui.database.ClassSnapshotParser.parseSnapshot(ClassSnapshotParser.java:15)
        at com.firebase.ui.common.BaseCachingSnapshotParser.parseSnapshot(BaseCachingSnapshotParser.java:35)
        at com.firebase.ui.common.BaseObservableSnapshotArray.get(BaseObservableSnapshotArray.java:52)
        at com.firebase.ui.database.FirebaseRecyclerAdapter.getItem(FirebaseRecyclerAdapter.java:106)
        at com.firebase.ui.database.FirebaseRecyclerAdapter.onBindViewHolder(FirebaseRecyclerAdapter.java:122)
        at androidx.recyclerview.widget.RecyclerView$Adapter.onBindViewHolder(RecyclerView.java:7065)
        at androidx.recyclerview.widget.RecyclerView$Adapter.bindViewHolder(RecyclerView.java:7107)
        at androidx.recyclerview.widget.RecyclerView$Recycler.tryBindViewHolderByDeadline(RecyclerView.java:6012)
        at androidx.recyclerview.widget.RecyclerView$Recycler.tryGetViewHolderForPositionByDeadline(RecyclerView.java:6279)
        at androidx.recyclerview.widget.RecyclerView$Recycler.getViewForPosition(RecyclerView.java:6118)
        at androidx.recyclerview.widget.RecyclerView$Recycler.getViewForPosition(RecyclerView.java:6114)
        at androidx.recyclerview.widget.LinearLayoutManager$LayoutState.next(LinearLayoutManager.java:2303)
        at androidx.recyclerview.widget.LinearLayoutManager.layoutChunk(LinearLayoutManager.java:1627)
        at androidx.recyclerview.widget.LinearLayoutManager.fill(LinearLayoutManager.java:1587)
        at androidx.recyclerview.widget.LinearLayoutManager.onLayoutChildren(LinearLayoutManager.java:665)
        at androidx.recyclerview.widget.RecyclerView.dispatchLayoutStep2(RecyclerView.java:4134)
        at androidx.recyclerview.widget.RecyclerView.dispatchLayout(RecyclerView.java:3851)
        at androidx.recyclerview.widget.RecyclerView.onLayout(RecyclerView.java:4404)
        at android.view.View.layout(View.java:22844)
        at android.view.ViewGroup.layout(ViewGroup.java:6389)
        at androidx.constraintlayout.widget.ConstraintLayout.onLayout(ConstraintLayout.java:1855)
        at android.view.View.layout(View.java:22844)
        at android.view.ViewGroup.layout(ViewGroup.java:6389)
        at android.widget.FrameLayout.layoutChildren(FrameLayout.java:332)
        at android.widget.FrameLayout.onLayout(FrameLayout.java:270)
        at android.view.View.layout(View.java:22844)
        at android.view.ViewGroup.layout(ViewGroup.java:6389)
        at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1829)
        at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1673)
        at android.widget.LinearLayout.onLayout(LinearLayout.java:1582)
        at android.view.View.layout(View.java:22844)
        at android.view.ViewGroup.layout(ViewGroup.java:6389)
        at android.widget.FrameLayout.layoutChildren(FrameLayout.java:332)
        at android.widget.FrameLayout.onLayout(FrameLayout.java:270)
        at android.view.View.layout(View.java:22844)
        at android.view.ViewGroup.layout(ViewGroup.java:6389)
        at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1829)
        at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1673)
        at android.widget.LinearLayout.onLayout(LinearLayout.java:1582)
        at android.view.View.layout(View.java:22844)
        at android.view.ViewGroup.layout(ViewGroup.java:6389)
        at android.widget.FrameLayout.layoutChildren(FrameLayout.java:332)
        at android.widget.FrameLayout.onLayout(FrameLayout.java:270)
2020-12-16 00:44:17.900 30685-30685 E/AndroidRuntime:     at com.android.internal.policy.DecorView.onLayout(DecorView.java:784)
        at android.view.View.layout(View.java:22844)
        at android.view.ViewGroup.layout(ViewGroup.java:6389)
        at android.view.ViewRootImpl.performLayout(ViewRootImpl.java:3470)
        at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:2938)
        at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1952)
        at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:8171)
        at android.view.Choreographer$CallbackRecord.run(Choreographer.java:972)
        at android.view.Choreographer.doCallbacks(Choreographer.java:796)
        at android.view.Choreographer.doFrame(Choreographer.java:731)
        at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:957)
        at android.os.Handler.handleCallback(Handler.java:938)
        at android.os.Handler.dispatchMessage(Handler.java:99)
        at android.os.Looper.loop(Looper.java:223)
        at android.app.ActivityThread.main(ActivityThread.java:7656)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:592)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:947)

这是我用来将所需子项提取到我的回收站视图中的 java 代码：

myRef = myfire.getReference().child("Data").child("Unseen");
        
        options1 = new FirebaseRecyclerOptions.Builder<model>()
                .setQuery(myRef, model.class)
                .build();
        FirebaseRecyclerAdapter<model, holder1> adapter = new FirebaseRecyclerAdapter<model, holder1>(options1) {
            @SuppressLint("SetTextI18n")
            @Override
            protected void onBindViewHolder( holder1 holder,   final int i, final model model) {
                final String set =getRef(i).getKey();
                holder.tvTopic.setText(set);


            }

            @NonNull
            @Override
            public holder1 onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
                View v = LayoutInflater.from(parent.getContext()).inflate(R.layout.item1, parent, false);
                return new holder1(v);
            }
        };
       

我的模型类是这样的：

public class model {

    public model() {
    }
}

我想再说一遍，我每次尝试都可以获取第二个孩子Unseen和第四个孩子0，但无法获取第三个孩子eeee强>。 我看不出问题出在哪里！

Answer 1

当您传入模型类时，FirebaseUI 会使用每个节点的值来填充该模型。由于您想在 UI 中使用 key，因此您需要使用自定义快照解析器，通过使用此 setQuery overload：

options1 = new FirebaseRecyclerOptions.Builder<model>()
        .setQuery(myRef, new SnapshotParser<String> {
            String parseSnapshot(@NonNull DataSnapshot snapshot) {
                return snapshot.getKey();
            }
        })
        .build();

Answer 2

看起来 Firebase 将项目转换为 List（因为它们看起来像一个数组），所以你需要类似的东西：

new FirebaseRecyclerOptions.Builder<model>()
        .setQuery(myRef, List.class)
        .build();

Answer 3

我找到了问题的解决方案。

当孩子是 ZERO（即 0）时，firebase 回收器视图不会显示上一个键。

我在 firebase 实时数据库中将第四个孩子“0”替换为“00”。

数据>> Unseen>> eeee>> 00>> stEnglish

令人惊讶的是它运行良好。