如何在片段中显示来自 firebase 实时数据库的 recyclerView 数据。 Android 工作室

Question

fragment_leaderboard.xml

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


<androidx.recyclerview.widget.RecyclerView
    android:id="@+id/recyclerView"
    android:layout_width="match_parent"
    android:layout_height="match_parent"/>
</FrameLayout>

row_leaderboard.xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout 
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:layout_width="match_parent"?
android:layout_height="wrap_content"
android:background="@color/cream">

<TextView
    android:id="@+id/index"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_marginStart="8dp"
    android:layout_marginLeft="8dp"
    android:fontFamily="@font/gotham_bold"
    android:text="#1"
    android:textColor="@color/brown"
    android:textSize="15sp"
    app:layout_constraintBottom_toBottomOf="@+id/imageView7"
    app:layout_constraintStart_toStartOf="parent"
    app:layout_constraintTop_toTopOf="@+id/imageView7" />

<ImageView
    android:id="@+id/imageView7"
    android:layout_width="32dp"
    android:layout_height="32dp"
    android:layout_marginStart="8dp"
    android:layout_marginLeft="8dp"
    android:layout_marginTop="8dp"
    android:layout_marginBottom="8dp"
    app:layout_constraintBottom_toBottomOf="parent"
    app:layout_constraintStart_toEndOf="@+id/index"
    app:layout_constraintTop_toTopOf="parent"
    app:srcCompat="@drawable/menu_profile2" />

<TextView
    android:id="@+id/name"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_marginStart="8dp"
    android:layout_marginLeft="8dp"
    android:fontFamily="@font/gotham_bold"
    android:text="Name of Winner"
    android:textColor="@color/brown"
    android:textSize="18sp"
    app:layout_constraintBottom_toBottomOf="@+id/imageView7"
    app:layout_constraintStart_toEndOf="@+id/imageView7"
    app:layout_constraintTop_toTopOf="@+id/imageView7" />

<TextView
    android:id="@+id/coins"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_marginEnd="8dp"
    android:layout_marginRight="8dp"
    android:fontFamily="@font/gotham_bold"
    android:text="1230"
    android:textColor="@color/brown"
    android:textSize="18sp"
    app:layout_constraintBottom_toBottomOf="@+id/name"
    app:layout_constraintEnd_toEndOf="parent"
    app:layout_constraintTop_toTopOf="@+id/name" />

 </androidx.constraintlayout.widget.ConstraintLayout>

LeaderBoardAdapter.java

package com.android.myquiz;

import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;

import androidx.annotation.NonNull;
import androidx.recyclerview.widget.RecyclerView;

import com.android.myquiz.databinding.RowLeaderboardBinding;

import org.jetbrains.annotations.NotNull;

import java.util.ArrayList;

public class LeaderBoardAdapter extends 
RecyclerView.Adapter<LeaderBoardAdapter.LeaderboardViewHolder>  {

 Context context;
 ArrayList<User> users;
 public  LeaderBoardAdapter(Context context, ArrayList<User> users){
     this.context = context;
     this.users = users;


 }

@NonNull
@NotNull
@Override
public LeaderboardViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType)

{ 查看 view = LayoutInflater.from(context).inflate(R.layout.row_leaderboard, parent, 错误的）; return 新的 LeaderboardViewHolder（视图）； }

@Override
public void onBindViewHolder(@NonNull LeaderboardViewHolder holder, int position) {
    User user = users.get(position);

    holder.binding.name.setText(user.getName1());
    holder.binding.coins.setText(String.valueOf(user.getCoins()));
    holder.binding.index.setText(String.format("#%d", position+1));


}

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

public class LeaderboardViewHolder extends RecyclerView.ViewHolder {

     TextView id;
    RowLeaderboardBinding binding;
    public LeaderboardViewHolder(@NonNull View itemView) {
        super(itemView);
        binding = RowLeaderboardBinding.bind(itemView);
    }
  }
}

LeaderboardFragments.java

package com.android.myquiz;

import android.os.Bundle;

import androidx.fragment.app.Fragment;
import androidx.recyclerview.widget.LinearLayoutManager;

import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;

import com.android.myquiz.databinding.FragmentLeaderboardsBinding;
import com.google.android.gms.tasks.OnSuccessListener;
import com.google.firebase.firestore.DocumentSnapshot;
import com.google.firebase.firestore.FirebaseFirestore;
import com.google.firebase.firestore.Query;
import com.google.firebase.firestore.QuerySnapshot;

import org.w3c.dom.Document;

import java.util.ArrayList;


public class LeaderboardsFragment extends Fragment {


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



@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

}

FragmentLeaderboardsBinding binding;

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle 
savedInstanceState) {
    // Inflate the layout for this fragment

    binding = FragmentLeaderboardsBinding.inflate(inflater, container,false);

    FirebaseFirestore database = FirebaseFirestore.getInstance();

    final ArrayList<User> users = new ArrayList<>();
    final LeaderBoardAdapter adapter = new LeaderBoardAdapter(getContext(), users);

    binding.recyclerView.setAdapter(adapter);
    binding.recyclerView.setLayoutManager(new LinearLayoutManager(getContext()));

    database.collection("users")
            .orderBy("coins", Query.Direction.DESCENDING).get().addOnSuccessListener(new 
OnSuccessListener<QuerySnapshot>() {
        @Override
        public void onSuccess(QuerySnapshot queryDocumentSnapshots) {
            for (DocumentSnapshot snapshot : queryDocumentSnapshots){
                User user = snapshot.toObject(User.class);
                users.add(user);

            }
            adapter.notifyDataSetChanged();
        }
    });
return binding.getRoot();
 }
}

这是我的代码，我想在片段中从实时数据库中的 recyclerView 中检索数据。

Answer 1

好的，看起来您可以从 firebase 获取数据，但是在设置数据时出错了。

当您调用 adapter.notifyDataSetChanged() 时，您需要注意将新的 users 列表传递给适配器。

您需要在适配器中创建一个方法 class,

public void setUsersList(ArrayList<User> users) {
       this.users = users;
       notifyDatasetChanged();
}

并在您的片段中调用它，例如 adapter.setUsersList(users)，而不是调用 adapter.notifyDataSetChanged().

如何在片段中显示来自 firebase 实时数据库的 recyclerView 数据。 Android 工作室

How to show the recyclerView data from firebase realtime database in fragments. Android studio

android

android-fragments

android-studio

android-recyclerview

firebase-realtime-database