很难让 Realtime RecyclerView FirebaseUI android 显示来自数据库的消息

Question

我在让 Android 应用的 RecyclerView 使用 Firebase 数据库中已有的数据填充 FirebaseUI 适配器时遇到困难，尽管我可以使用以下方式向其发送数据：

public void onAdd(View v){
    //create Firebase Object
    t=(EditText) findViewById(R.id.display);
    String mitems=t.getText().toString();
    myRef.push().setValue(mitems.toString());
}

我使用了以下方法来接收我发送的数据，但它不起作用：

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    //Recycler
    recyclerView=(RecyclerView)findViewById(R.id.messageRecyclerView);
    recyclerView.setHasFixedSize(true);
    recyclerView.setLayoutManager(new LinearLayoutManager(this));

    //Adapter
    FirebaseRecyclerAdapter<String, MessageViewHolder> mFirebaseAdapter=
        new FirebaseRecyclerAdapter<String, MessageViewHolder>(
                String.class,
                android.R.layout.simple_list_item_1,
                MessageViewHolder.class,
                myRef.child("Message")
                ) {
                    @Override
                    protected void populateViewHolder(MessageViewHolder viewHolder, String model, int position) {
                        viewHolder.messageTextView.setText(model.toString());
                }
            };
    recyclerView.setAdapter(mFirebaseAdapter);
}

我的 ViewHolder 是这样定义的：

static class MessageViewHolder extends RecyclerView.ViewHolder {
    public TextView messageTextView;

    MessageViewHolder(View view) {
        super(view);
        messageTextView = (TextView)view.findViewById(android.R.id.text1);
    }
}

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">

    <android.support.v7.widget.RecyclerView
        android:id="@+id/messageRecyclerView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"

        />
    <EditText
        android:hint="Enter Text"
        android:id="@+id/display"
        android:textColor="@color/colorAccent"
        android:background="@color/colorPrimary"
        android:padding="10dp"
        android:layout_width="match_parent" android:layout_height="wrap_content"/>
    <Button android:layout_height="wrap_content"
        android:layout_width="match_parent"
        android:text="ADD ITEM"
        android:onClick="onAdd"
        />

</LinearLayout>

这是错误消息：

Exception java.lang.ClassCastException: android.support.v7.widget.AppCompatTextView cannot be cast to android.view.ViewGroup
com.firebase.ui.database.FirebaseRecyclerAdapter.onCreateViewHolder (FirebaseRecyclerAdapter.java:160)
android.support.v7.widget.RecyclerView$Adapter.createViewHolder (RecyclerView.java:6073)
android.support.v7.widget.RecyclerView$Recycler.getViewForPosition (RecyclerView.java:5243)
android.support.v7.widget.RecyclerView$Recycler.getViewForPosition (RecyclerView.java:5153)
android.support.v7.widget.LinearLayoutManager$LayoutState.next (LinearLayoutManager.java:2061)
android.support.v7.widget.LinearLayoutManager.layoutChunk (LinearLayoutManager.java:1445)
android.support.v7.widget.LinearLayoutManager.fill (LinearLayoutManager.java:1408)
android.support.v7.widget.LinearLayoutManager.onLayoutChildren (LinearLayoutManager.java:580)
android.support.v7.widget.RecyclerView.dispatchLayoutStep2 (RecyclerView.java:3374)
android.support.v7.widget.RecyclerView.dispatchLayout (RecyclerView.java:3183)
android.support.v7.widget.RecyclerView.consumePendingUpdateOperations (RecyclerView.java:1593)
android.support.v7.widget.RecyclerView.run (RecyclerView.java:323)
android.view.Choreographer$CallbackRecord.run (Choreographer.java:788)
android.view.Choreographer.doCallbacks (Choreographer.java:591)
android.view.Choreographer.doFrame (Choreographer.java:559)
android.view.Choreographer$FrameDisplayEventReceiver.run (Choreographer.java:774)
android.os.Handler.handleCallback (Handler.java:808)
android.os.Handler.dispatchMessage (Handler.java:103)
android.os.Looper.loop (Looper.java:193)
android.app.ActivityThread.main (ActivityThread.java:5299)
java.lang.reflect.Method.invokeNative (Method.java)
java.lang.reflect.Method.invoke (Method.java:515)
com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run (ZygoteInit.java:829)
com.android.internal.os.ZygoteInit.main (ZygoteInit.java:645)
dalvik.system.NativeStart.main (NativeStart.java)

Answer 1

替换

        //Adapter
    FirebaseRecyclerAdapter<String, MessageViewHolder> mFirebaseAdapter=
            new FirebaseRecyclerAdapter<String, MessageViewHolder>(
                    String.class,
                    android.R.layout.simple_list_item_1,
                    MessageViewHolder.class,
                    myRef.child("Message")
            )

和

    //Adapter
    FirebaseRecyclerAdapter<String, MessageViewHolder> mFirebaseAdapter=
            new FirebaseRecyclerAdapter<String, MessageViewHolder>(
                    String.class,
                    android.R.layout.simple_list_item_1,
                    MessageViewHolder.class,
                    myRef
            )

将 myRef.child("Message") 替换为 myRef。基于您的 onAdd 方法。

Answer 2

我解决这个问题的第一次尝试是专注于我怀疑没有 work.From 错误消息的卡盘，

Exception 
java.lang.ClassCastException:android.support.v7.widget.AppCompatTextView 
cannot be cast to android.view.ViewGroup

我最好的猜测是 RecyclerView 及其对应 FirebaseRecyclerAdapter.I 将其替换为 ListView 及其相应的 FirebaseListAdapter 因此：

ListView ml=(ListView) findViewById(R.id.listview);

     FirebaseListAdapter<String> adapter=new FirebaseListAdapter<String>(this,String.class,android.R.layout.simple_list_item_1,myRef.child("Message"))
     {
         @Override
         protected void populateView(View v, String model, int position) {
             TextView tv=(TextView) v.findViewById(android.R.id.text1) ;
             tv.setText(model);

         }
     };
     ml.setAdapter(adapter) ;

ListView 有效；从而确认 Firebase 数据库正常 formed.I 继续使用 RecyclerView re-develop 应用程序，我意识到第一个问题（即使在成功清理项目之后）viz:android studio 添加了一个版本的编译代码到我的 build.graddle 文件即： compile 'com.android.support:recyclerview-v7:25.0.0' 这与我的 sdk 版本 24.2 不同。1.Hence 我应用了以下更正即：

compile 'com.android.support:recyclerview-v7:24.2.1'

总的来说，这个更正只是阻止了应用程序崩溃，但没有解决显示我的 data.The 列表的问题 link 解决了主要问题 - casting.The link 是此平台上 cast-error-with-firebaserecyclerviewadapter 上的。所以我跟着它，它奏效了。

很难让 Realtime RecyclerView FirebaseUI android 显示来自数据库的消息

Difficulties getting Realtime RecyclerView FirebaseUI android to show messages from database

java

android

firebaseui