如何在社交媒体Android应用中显示所有注册用户？

这是8的“建立一个社交媒体应用程序在Android工作室”教程中的一部分，我们将要在本文中介绍了以下功能：

• 我们将显示我们应用程序的所有注册用户。
• 我们将在UsersFragment中显示用户列表。

分步实施

步骤1：建立新的Java类别

与ModelUsers一起工作。 Java文件。创建此活动以初始化密钥，以便我们以后可以检索密钥的值。

Java

package com.example.socialmediaapp;
  
public class ModelUsers {
    String name;
  
    public ModelUsers() {
    }
  
    String onlineStatus;
    String typingTo;
  
    public String getName() {
        return name;
    }
  
    public void setName(String name) {
        this.name = name;
    }
  
    public String getTypingTo() {
        return typingTo;
    }
  
    public void setTypingTo(String typingTo) {
        this.typingTo = typingTo;
    }
  
    public String getEmail() {
        return email;
    }
  
    public void setEmail(String email) {
        this.email = email;
    }
  
    public String getImage() {
        return image;
    }
  
    public void setImage(String image) {
        this.image = image;
    }
  
    public String getUid() {
        return uid;
    }
  
    public void setUid(String uid) {
        this.uid = uid;
    }
  
    public ModelUsers(String name, String onlineStatus, String typingTo, String email, String image, String uid) {
        this.name = name;
        this.onlineStatus = onlineStatus;
        this.typingTo = typingTo;
        this.email = email;
        this.image = image;
        this.uid = uid;
    }
  
    String email;
      
    String image;
  
    String uid;
}

步骤2：建立另一个新的Java类别

使用AdapterUsers。 Java文件。

Java

package com.example.socialmediaapp;
  
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.bumptech.glide.Glide;
import com.google.firebase.auth.FirebaseAuth;
  
import java.util.List;
  
import de.hdodenhof.circleimageview.CircleImageView;
  
public class AdapterUsers extends RecyclerView.Adapter {
  
    Context context;
    FirebaseAuth firebaseAuth;
    String uid;
  
    public AdapterUsers(Context context, List list) {
        this.context = context;
        this.list = list;
        firebaseAuth = FirebaseAuth.getInstance();
        uid = firebaseAuth.getUid();
    }
  
    List list;
  
    @NonNull
    @Override
    public MyHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
        View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.row_users, parent, false);
        return new MyHolder(view);
    }
  
    @Override
    public void onBindViewHolder(@NonNull MyHolder holder, final int position) {
        final String hisuid = list.get(position).getUid();
        String userImage = list.get(position).getImage();
        String username = list.get(position).getName();
        String usermail = list.get(position).getEmail();
        holder.name.setText(username);
        holder.email.setText(usermail);
        try {
            Glide.with(context).load(userImage).into(holder.profiletv);
        } catch (Exception e) {
        }
    }
      
    @Override
    public int getItemCount() {
        return list.size();
    }
  
    class MyHolder extends RecyclerView.ViewHolder {
  
        CircleImageView profiletv;
        TextView name, email;
  
        public MyHolder(@NonNull View itemView) {
            super(itemView);
            profiletv = itemView.findViewById(R.id.imagep);
            name = itemView.findViewById(R.id.namep);
            email = itemView.findViewById(R.id.emailp);
        }
    }
}

步骤3：使用fragment_user.xml文件

导航至应用程序> res>布局> fragment_user.xml，然后将以下代码添加到该文件中。以下是fragment_user.xml文件的代码。

步骤4：使用row_users.xml文件

创建一个新的布局资源文件，并将其命名为row_users 。以下是row_users.xml文件的代码。

步骤5：使用UsersFragmnet。 Java文件

转到UsersFragmnet。 Java文件并参考以下代码。下面是UsersFragmnet的代码。 Java文件。

Java

package com.example.socialmediaapp;
  
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
  
import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.fragment.app.Fragment;
import androidx.recyclerview.widget.LinearLayoutManager;
import androidx.recyclerview.widget.RecyclerView;
  
import com.google.firebase.auth.FirebaseAuth;
import com.google.firebase.auth.FirebaseUser;
import com.google.firebase.database.DataSnapshot;
import com.google.firebase.database.DatabaseError;
import com.google.firebase.database.DatabaseReference;
import com.google.firebase.database.FirebaseDatabase;
import com.google.firebase.database.ValueEventListener;
  
import java.util.ArrayList;
import java.util.List;
  
/**
 * A simple {@link Fragment} subclass.
 */
public class UsersFragment extends Fragment {
  
    RecyclerView recyclerView;
    AdapterUsers adapterUsers;
    List usersList;
    FirebaseAuth firebaseAuth;
  
    public UsersFragment() {
        // Required empty public constructor
    }
  
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        // Inflate the layout for this fragment
        View view = inflater.inflate(R.layout.fragment_users, container, false);
        recyclerView = view.findViewById(R.id.recyclep);
        recyclerView.setHasFixedSize(true);
        recyclerView.setLayoutManager(new LinearLayoutManager(getActivity()));
        usersList = new ArrayList<>();
        firebaseAuth = FirebaseAuth.getInstance();
        getAllUsers();
        return view;
    }
  
    private void getAllUsers() {
        final FirebaseUser firebaseUser = FirebaseAuth.getInstance().getCurrentUser();
        DatabaseReference reference = FirebaseDatabase.getInstance().getReference("Users");
        reference.addValueEventListener(new ValueEventListener() {
            @Override
            public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
                usersList.clear();
                for (DataSnapshot dataSnapshot1 : dataSnapshot.getChildren()) {
                    ModelUsers modelUsers = dataSnapshot1.getValue(ModelUsers.class);
                    if (modelUsers.getUid() != null && !modelUsers.getUid().equals(firebaseUser.getUid())) {
                        usersList.add(modelUsers);
                    }
                    adapterUsers = new AdapterUsers(getActivity(), usersList);
                    recyclerView.setAdapter(adapterUsers);
                }
            }
  
            @Override
            public void onCancelled(@NonNull DatabaseError databaseError) {
  
            }
        });
    }
  
    @Override
    public void onCreate(@Nullable Bundle savedInstanceState) {
        setHasOptionsMenu(true);
        super.onCreate(savedInstanceState);
    }
}

输出：

对于本文中使用的所有可绘制文件，请参考以下链接： https://drive.google.com/drive/folders/1M_knOH_ugCuwSP5nkYzeD4dRp-Honzbe?usp=sharing

下面是执行这些操作后的文件结构：