如何在社交媒体Android应用中实现聊天功能？

这是14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：

• 我们将为聊天创建布局并在聊天中发送消息。
• 用户可以发送消息或图像。
• 用户可以使用相机或图库发送图像。
• 首先，将要求许可请求使用图库发送图像，或使用相机单击图像后发送图像。
• 如果已授予许可，则用户可以发送图像，否则它将再次请求询问许可。

分步实施

步骤1：创建两个新的布局资源文件，并将其命名为row_chat_left和row_chat_right

使用row_chat_left.xml文件。收到的消息将在左侧。同样，使用row_chat_right 。 xml文件。发送给用户的消息将在右侧。以下是row_chat_left.xml文件和row_chat_right的代码。 xml文件。

步骤2：使用activity_chat.xml文件

在这里，我们将在RecyclerView中显示所有消息。在TextView中，用户将键入消息，然后使用发送按钮，用户将发送消息。以下是activity_chat.xml文件的代码。

步骤3：使用row_chatlist.xml文件

创建另一个布局资源文件，并将文件命名为row_chatlist 。下面是row_chatlist.xml文件的代码。

步骤4：使用ModelChat。 Java文件

创建了此类以初始化密钥，以便我们以后可以检索密钥的值。

Java

package com.example.socialmediaapp;
  
public class ModelChat {
    String message;
  
  
    public String getMessage() {
        return message;
    }
  
    public void setMessage(String message) {
        this.message = message;
    }
  
    public String getReceiver() {
        return receiver;
    }
  
    public void setReceiver(String receiver) {
        this.receiver = receiver;
    }
  
    public String getSender() {
        return sender;
    }
  
    public void setSender(String sender) {
        this.sender = sender;
    }
  
    public String getTimestamp() {
        return timestamp;
    }
  
    public void setTimestamp(String timestamp) {
        this.timestamp = timestamp;
    }
  
    public boolean isDilihat() {
        return dilihat;
    }
  
    public void setDilihat(boolean dilihat) {
        this.dilihat = dilihat;
    }
  
    String receiver;
  
    public ModelChat() {
    }
  
    String sender;
  
    public String getType() {
        return type;
    }
  
    public void setType(String type) {
        this.type = type;
    }
  
    public ModelChat(String message, String receiver, String sender, String type, String timestamp, boolean dilihat) {
        this.message = message;
        this.receiver = receiver;
        this.sender = sender;
        this.type = type;
        this.timestamp = timestamp;
        this.dilihat = dilihat;
    }
  
    String type;
  
  
    String timestamp;
  
  
    boolean dilihat;
}

第5步：使用AdpaterChat。 Java文件

创建一个新的Java类，并将该类命名为AdpaterChat。以下是AdpaterChat的代码。 Java文件。

Java

package com.example.socialmediaapp;
  
import android.app.AlertDialog;
import android.content.Context;
import android.content.DialogInterface;
import android.text.format.DateFormat;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ImageView;
import android.widget.LinearLayout;
import android.widget.TextView;
import android.widget.Toast;
  
import androidx.annotation.NonNull;
import androidx.recyclerview.widget.RecyclerView;
  
import com.bumptech.glide.Glide;
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.Query;
import com.google.firebase.database.ValueEventListener;
  
import java.util.Calendar;
import java.util.List;
import java.util.Locale;
  
import de.hdodenhof.circleimageview.CircleImageView;
  
public class AdapterChat extends RecyclerView.Adapter {
    private static final int MSG_TYPE_LEFT = 0;
    private static final int MSG_TYPR_RIGHT = 1;
    Context context;
    List list;
    String imageurl;
    FirebaseUser firebaseUser;
  
    public AdapterChat(Context context, List list, String imageurl) {
        this.context = context;
        this.list = list;
        this.imageurl = imageurl;
    }
  
    @NonNull
    @Override
    public Myholder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
        if (viewType == MSG_TYPE_LEFT) {
            View view = LayoutInflater.from(context).inflate(R.layout.row_chat_left, parent, false);
            return new Myholder(view);
        } else {
            View view = LayoutInflater.from(context).inflate(R.layout.row_chat_right, parent, false);
            return new Myholder(view);
        }
    }
  
    @Override
    public void onBindViewHolder(@NonNull Myholder holder, final int position) {
        String message = list.get(position).getMessage();
        String timeStamp = list.get(position).getTimestamp();
        String type = list.get(position).getType();
        Calendar calendar = Calendar.getInstance(Locale.ENGLISH);
        calendar.setTimeInMillis(Long.parseLong(timeStamp));
        String timedate = DateFormat.format("dd/MM/yyyy hh:mm aa", calendar).toString();
        holder.message.setText(message);
        holder.time.setText(timedate);
        try {
            Glide.with(context).load(imageurl).into(holder.image);
        } catch (Exception e) {
  
        }
        if (type.equals("text")) {
            holder.message.setVisibility(View.VISIBLE);
            holder.mimage.setVisibility(View.GONE);
            holder.message.setText(message);
        } else {
            holder.message.setVisibility(View.GONE);
            holder.mimage.setVisibility(View.VISIBLE);
            Glide.with(context).load(message).into(holder.mimage);
        }
  
        holder.msglayput.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                AlertDialog.Builder builder = new AlertDialog.Builder(context);
                builder.setTitle("Delete Message");
                builder.setMessage("Are You Sure To Delete This Messgae");
                builder.setPositiveButton("Delete", new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialog, int which) {
                        deleteMsg(position);
                    }
                });
                builder.setNegativeButton("Cancel", new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialog, int which) {
                        dialog.dismiss();
                    }
                });
                builder.create().show();
            }
        });
    }
  
    private void deleteMsg(int position) {
        final String myuid = FirebaseAuth.getInstance().getCurrentUser().getUid();
        String msgtimestmp = list.get(position).getTimestamp();
        DatabaseReference dbref = FirebaseDatabase.getInstance().getReference().child("Chats");
        Query query = dbref.orderByChild("timestamp").equalTo(msgtimestmp);
        query.addListenerForSingleValueEvent(new ValueEventListener() {
            @Override
            public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
                for (DataSnapshot dataSnapshot1 : dataSnapshot.getChildren()) {
                    if (dataSnapshot1.child("sender").getValue().equals(myuid)) {
                        // any two of below can be used
                        dataSnapshot1.getRef().removeValue();
                       /* HashMap hashMap = new HashMap<>();
                        hashMap.put("message", "This Message Was Deleted");
                        dataSnapshot1.getRef().updateChildren(hashMap);
                        Toast.makeText(context,"Message Deleted.....",Toast.LENGTH_LONG).show();
*/
                    } else {
                        Toast.makeText(context, "you can delet only your msg....", Toast.LENGTH_LONG).show();
                    }
                }
            }
  
            @Override
            public void onCancelled(@NonNull DatabaseError databaseError) {
  
            }
        });
    }
  
    @Override
    public int getItemCount() {
        return list.size();
    }
  
    @Override
    public int getItemViewType(int position) {
        firebaseUser = FirebaseAuth.getInstance().getCurrentUser();
        if (list.get(position).getSender().equals(firebaseUser.getUid())) {
            return MSG_TYPR_RIGHT;
        } else {
            return MSG_TYPE_LEFT;
        }
    }
  
    class Myholder extends RecyclerView.ViewHolder {
  
        CircleImageView image;
        ImageView mimage;
        TextView message, time, isSee;
        LinearLayout msglayput;
  
        public Myholder(@NonNull View itemView) {
            super(itemView);
            image = itemView.findViewById(R.id.profilec);
            message = itemView.findViewById(R.id.msgc);
            time = itemView.findViewById(R.id.timetv);
            isSee = itemView.findViewById(R.id.isSeen);
            msglayput = itemView.findViewById(R.id.msglayout);
            mimage = itemView.findViewById(R.id.images);
        }
    }
}

步骤6：使用ChatActivity。 Java文件

我们正在从Firebase的“聊天”节点中读取用户消息。每次数据更改时，此数据也会相应更改

chatList=new ArrayList<>();
DatabaseReference dbref= FirebaseDatabase.getInstance().getReference().child("Chats");

使用适配器聊天加载数据设置数据值

ModelChat modelChat=dataSnapshot1.getValue(ModelChat.class);
                    if(modelChat.getSender().equals(myuid)&&
                            modelChat.getReceiver().equals(uid)||
                            modelChat.getReceiver().equals(myuid)
                                    && modelChat.getSender().equals(uid)){
                        chatList.add(modelChat);//add the chat in chatlist
                    }
                    adapterChat=new AdapterChat(ChatActivity.this,chatList,image);
                    adapterChat.notifyDataSetChanged();
                    recyclerView.setAdapter(adapterChat);

在“聊天参考”中的“发送消息”节点值。这是我们如何在Firebase Realtime数据库中保存数据

DatabaseReference databaseReference= FirebaseDatabase.getInstance().getReference();
        String timestamp=String.valueOf(System.currentTimeMillis());
        HashMap hashMap=new HashMap<>();
        hashMap.put("sender",myuid);
        hashMap.put("receiver",uid);
        hashMap.put("message",message);
        hashMap.put("timestamp",timestamp);
        hashMap.put("dilihat",false);
        hashMap.put("type","text");
        databaseReference.child("Chats").push().setValue(hashMap);

下面是ChatActivity的代码。 Java文件。

Java

package com.example.socialmediaapp;
  
import android.Manifest;
import android.app.AlertDialog;
import android.app.ProgressDialog;
import android.content.ContentValues;
import android.content.DialogInterface;
import android.content.Intent;
import android.content.pm.PackageManager;
import android.graphics.Bitmap;
import android.net.Uri;
import android.os.Bundle;
import android.provider.MediaStore;
import android.text.TextUtils;
import android.text.format.DateFormat;
import android.view.MenuItem;
import android.view.View;
import android.widget.EditText;
import android.widget.ImageButton;
import android.widget.ImageView;
import android.widget.TextView;
import android.widget.Toast;
  
import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.appcompat.app.AppCompatActivity;
import androidx.appcompat.widget.Toolbar;
import androidx.core.content.ContextCompat;
import androidx.recyclerview.widget.LinearLayoutManager;
import androidx.recyclerview.widget.RecyclerView;
  
import com.bumptech.glide.Glide;
import com.google.android.gms.tasks.OnFailureListener;
import com.google.android.gms.tasks.OnSuccessListener;
import com.google.android.gms.tasks.Task;
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.Query;
import com.google.firebase.database.ValueEventListener;
import com.google.firebase.storage.FirebaseStorage;
import com.google.firebase.storage.StorageReference;
import com.google.firebase.storage.UploadTask;
  
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Calendar;
import java.util.HashMap;
import java.util.List;
  
  
public class ChatActivity extends AppCompatActivity {
    Toolbar toolbar;
    RecyclerView recyclerView;
    ImageView profile, block;
    TextView name, userstatus;
    EditText msg;
    ImageButton send, attach;
    FirebaseAuth firebaseAuth;
    String uid, myuid, image;
    ValueEventListener valueEventListener;
    List chatList;
    AdapterChat adapterChat;
  
    private static final int IMAGEPICK_GALLERY_REQUEST = 300;
    private static final int IMAGE_PICKCAMERA_REQUEST = 400;
    private static final int CAMERA_REQUEST = 100;
    private static final int STORAGE_REQUEST = 200;
    String cameraPermission[];
    String storagePermission[];
    Uri imageuri = null;
    FirebaseDatabase firebaseDatabase;
    DatabaseReference users;
    boolean notify = false;
    boolean isBlocked = false;
  
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_chat);
        firebaseAuth = FirebaseAuth.getInstance();
          
        // initialise the text views and layouts
        profile = findViewById(R.id.profiletv);
        name = findViewById(R.id.nameptv);
        userstatus = findViewById(R.id.onlinetv);
        msg = findViewById(R.id.messaget);
        send = findViewById(R.id.sendmsg);
        attach = findViewById(R.id.attachbtn);
        block = findViewById(R.id.block);
        LinearLayoutManager linearLayoutManager = new LinearLayoutManager(this);
        linearLayoutManager.setStackFromEnd(true);
        recyclerView = findViewById(R.id.chatrecycle);
        recyclerView.setHasFixedSize(true);
        recyclerView.setLayoutManager(linearLayoutManager);
        uid = getIntent().getStringExtra("uid");
          
        // getting uid of another user using intent
        firebaseDatabase = FirebaseDatabase.getInstance();
          
        // initialising permissions
        cameraPermission = new String[]{Manifest.permission.CAMERA, Manifest.permission.WRITE_EXTERNAL_STORAGE};
        storagePermission = new String[]{Manifest.permission.WRITE_EXTERNAL_STORAGE};
  
        checkUserStatus();
        users = firebaseDatabase.getReference("Users");
        attach.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                showImagePicDialog();
            }
        });
        send.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                notify = true;
                String message = msg.getText().toString().trim();
                if (TextUtils.isEmpty(message)) {//if empty
                    Toast.makeText(ChatActivity.this, "Please Write Something Here", Toast.LENGTH_LONG).show();
                } else {
                    sendmessage(message);
                }
                msg.setText("");
            }
        });
          
        Query userquery = users.orderByChild("uid").equalTo(uid);
        userquery.addValueEventListener(new ValueEventListener() {
            @Override
            public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
                // retrieve user data
                for (DataSnapshot dataSnapshot1 : dataSnapshot.getChildren()) {
                    String nameh = "" + dataSnapshot1.child("name").getValue();
                    image = "" + dataSnapshot1.child("image").getValue();
                    String onlinestatus = "" + dataSnapshot1.child("onlineStatus").getValue();
                    String typingto = "" + dataSnapshot1.child("typingTo").getValue();
                    if (typingto.equals(myuid)) {// if user is typing to my chat
                        userstatus.setText("Typing....");// type status as typing
                    } else {
                        if (onlinestatus.equals("online")) {
                            userstatus.setText(onlinestatus);
                        } else {
                            Calendar calendar = Calendar.getInstance();
                            calendar.setTimeInMillis(Long.parseLong(onlinestatus));
                            String timedate = DateFormat.format("dd/MM/yyyy hh:mm aa", calendar).toString();
                            userstatus.setText("Last Seen:" + timedate);
                        }
                    }
                    name.setText(nameh);
                    try {
                        Glide.with(ChatActivity.this).load(image).placeholder(R.drawable.profile_image).into(profile);
                    } catch (Exception e) {
  
                    }
                }
            }
  
            @Override
            public void onCancelled(@NonNull DatabaseError databaseError) {
  
            }
        });
        readMessages();
    }
  
  
    @Override
    protected void onPause() {
        super.onPause();
        String timestamp = String.valueOf(System.currentTimeMillis());
        checkOnlineStatus(timestamp);
        checkTypingStatus("noOne");
    }
  
    @Override
    protected void onResume() {
        checkOnlineStatus("online");
        super.onResume();
    }
  
    @Override
    public boolean onSupportNavigateUp() {
        onBackPressed();
        return super.onSupportNavigateUp();
    }
  
    private void checkOnlineStatus(String status) {
        // check online status
        DatabaseReference dbref = FirebaseDatabase.getInstance().getReference("Users").child(myuid);
        HashMap hashMap = new HashMap<>();
        hashMap.put("onlineStatus", status);
        dbref.updateChildren(hashMap);
    }
  
    private void checkTypingStatus(String typing) {
        DatabaseReference dbref = FirebaseDatabase.getInstance().getReference("Users").child(myuid);
        HashMap hashMap = new HashMap<>();
        hashMap.put("typingTo", typing);
        dbref.updateChildren(hashMap);
    }
  
    @Override
    protected void onStart() {
        checkUserStatus();
        checkOnlineStatus("online");
        super.onStart();
    }
  
    private void readMessages() {
        // show message after retrieving data
        chatList = new ArrayList<>();
        DatabaseReference dbref = FirebaseDatabase.getInstance().getReference().child("Chats");
        dbref.addValueEventListener(new ValueEventListener() {
            @Override
            public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
  
                chatList.clear();
                for (DataSnapshot dataSnapshot1 : dataSnapshot.getChildren()) {
                    ModelChat modelChat = dataSnapshot1.getValue(ModelChat.class);
                    if (modelChat.getSender().equals(myuid) &&
                            modelChat.getReceiver().equals(uid) ||
                            modelChat.getReceiver().equals(myuid)
                                    && modelChat.getSender().equals(uid)) {
                        chatList.add(modelChat); // add the chat in chatlist
                    }
                    adapterChat = new AdapterChat(ChatActivity.this, chatList, image);
                    adapterChat.notifyDataSetChanged();
                    recyclerView.setAdapter(adapterChat);
                }
            }
  
            @Override
            public void onCancelled(@NonNull DatabaseError databaseError) {
  
            }
        });
    }
  
    private void showImagePicDialog() {
        String options[] = {"Camera", "Gallery"};
        AlertDialog.Builder builder = new AlertDialog.Builder(ChatActivity.this);
        builder.setTitle("Pick Image From");
        builder.setItems(options, new DialogInterface.OnClickListener() {
            @Override
            public void onClick(DialogInterface dialog, int which) {
  
                if (which == 0) {
                    if (!checkCameraPermission()) { // if permission is not given
                        requestCameraPermission(); // request for permission
                    } else {
                        pickFromCamera(); // if already access granted then click
                    }
                } else if (which == 1) {
                    if (!checkStoragePermission()) { // if permission is not given
                        requestStoragePermission(); // request for permission
                    } else {
                        pickFromGallery(); // if already access granted then pick
                    }
                }
            }
        });
        builder.create().show();
    }
  
    public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
        // request for permission if not given
        switch (requestCode) {
            case CAMERA_REQUEST: {
                if (grantResults.length > 0) {
                    boolean camera_accepted = grantResults[0] == PackageManager.PERMISSION_GRANTED;
                    boolean writeStorageaccepted = grantResults[1] == PackageManager.PERMISSION_GRANTED;
                    if (camera_accepted && writeStorageaccepted) {
                        pickFromCamera(); // if access granted then click
                    } else {
                        Toast.makeText(this, "Please Enable Camera and Storage Permissions", Toast.LENGTH_LONG).show();
                    }
                }
            }
            break;
            case STORAGE_REQUEST: {
                if (grantResults.length > 0) {
                    boolean writeStorageaccepted = grantResults[0] == PackageManager.PERMISSION_GRANTED;
                    if (writeStorageaccepted) {
                        pickFromGallery(); // if access granted then pick
                    } else {
                        Toast.makeText(this, "Please Enable Storage Permissions", Toast.LENGTH_LONG).show();
                    }
                }
            }
            break;
        }
    }
  
    @Override
    public void onActivityResult(int requestCode, int resultCode, @Nullable Intent data) {
        if (resultCode == RESULT_OK) {
            if (requestCode == IMAGEPICK_GALLERY_REQUEST) {
                imageuri = data.getData(); // get image data to upload
                try {
                    sendImageMessage(imageuri);
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            if (requestCode == IMAGE_PICKCAMERA_REQUEST) {
                try {
                    sendImageMessage(imageuri);
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
        super.onActivityResult(requestCode, resultCode, data);
    }
  
    private void sendImageMessage(Uri imageuri) throws IOException {
        notify = true;
        final ProgressDialog dialog = new ProgressDialog(this);
        dialog.setMessage("Sending Image");
        dialog.show();
          
        // If we are sending image as a message
        // then we need to find the url of
        // image after uploading the
        // image in firebase storage
        final String timestamp = "" + System.currentTimeMillis();
        String filepathandname = "ChatImages/" + "post" + timestamp; // filename
        Bitmap bitmap = MediaStore.Images.Media.getBitmap(this.getContentResolver(), imageuri);
        ByteArrayOutputStream arrayOutputStream = new ByteArrayOutputStream();
        bitmap.compress(Bitmap.CompressFormat.PNG, 100, arrayOutputStream); // compressing the image using bitmap
        final byte[] data = arrayOutputStream.toByteArray();
        StorageReference ref = FirebaseStorage.getInstance().getReference().child(filepathandname);
        ref.putBytes(data).addOnSuccessListener(new OnSuccessListener() {
            @Override
            public void onSuccess(UploadTask.TaskSnapshot taskSnapshot) {
                dialog.dismiss();
                Task uriTask = taskSnapshot.getStorage().getDownloadUrl();
                while (!uriTask.isSuccessful()) ;
                String downloadUri = uriTask.getResult().toString(); // getting url if task is successful
  
                if (uriTask.isSuccessful()) {
                    DatabaseReference re = FirebaseDatabase.getInstance().getReference();
                    HashMap hashMap = new HashMap<>();
                    hashMap.put("sender", myuid);
                    hashMap.put("receiver", uid);
                    hashMap.put("message", downloadUri);
                    hashMap.put("timestamp", timestamp);
                    hashMap.put("dilihat", false);
                    hashMap.put("type", "images");
                    re.child("Chats").push().setValue(hashMap); // push in firebase using unique id
                    final DatabaseReference ref1 = FirebaseDatabase.getInstance().getReference("ChatList").child(uid).child(myuid);
                    ref1.addValueEventListener(new ValueEventListener() {
                        @Override
                        public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
                            if (!dataSnapshot.exists()) {
                                ref1.child("id").setValue(myuid);
                            }
                        }
  
                        @Override
                        public void onCancelled(@NonNull DatabaseError databaseError) {
  
                        }
                    });
                    final DatabaseReference ref2 = FirebaseDatabase.getInstance().getReference("ChatList").child(myuid).child(uid);
                    ref2.addValueEventListener(new ValueEventListener() {
                        @Override
                        public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
                            if (!dataSnapshot.exists()) {
                                ref2.child("id").setValue(uid);
                            }
                        }
  
                        @Override
                        public void onCancelled(@NonNull DatabaseError databaseError) {
  
                        }
                    });
                }
            }
        }).addOnFailureListener(new OnFailureListener() {
            @Override
            public void onFailure(@NonNull Exception e) {
  
            }
        });
    }
  
    private Boolean checkCameraPermission() {
        boolean result = ContextCompat.checkSelfPermission(this, Manifest.permission.CAMERA) == (PackageManager.PERMISSION_GRANTED);
        boolean result1 = ContextCompat.checkSelfPermission(this, Manifest.permission.WRITE_EXTERNAL_STORAGE) == (PackageManager.PERMISSION_GRANTED);
        return result && result1;
    }
  
    private void requestCameraPermission() {
        requestPermissions(cameraPermission, CAMERA_REQUEST);
    }
  
    private void pickFromCamera() {
        ContentValues contentValues = new ContentValues();
        contentValues.put(MediaStore.Images.Media.TITLE, "Temp_pic");
        contentValues.put(MediaStore.Images.Media.DESCRIPTION, "Temp Description");
        imageuri = this.getContentResolver().insert(MediaStore.Images.Media.EXTERNAL_CONTENT_URI, contentValues);
        Intent camerIntent = new Intent(MediaStore.ACTION_IMAGE_CAPTURE);
        camerIntent.putExtra(MediaStore.EXTRA_OUTPUT, imageuri);
        startActivityForResult(camerIntent, IMAGE_PICKCAMERA_REQUEST);
    }
  
    private void pickFromGallery() {
        Intent galleryIntent = new Intent(Intent.ACTION_PICK);
        galleryIntent.setType("image/*");
        startActivityForResult(galleryIntent, IMAGEPICK_GALLERY_REQUEST);
    }
  
    private Boolean checkStoragePermission() {
        boolean result = ContextCompat.checkSelfPermission(ChatActivity.this, Manifest.permission.WRITE_EXTERNAL_STORAGE) == (PackageManager.PERMISSION_GRANTED);
        return result;
    }
  
    private void requestStoragePermission() {
        requestPermissions(storagePermission, STORAGE_REQUEST);
    }
  
    private void sendmessage(final String message) {
        // creating a reference to store data in firebase
        // We will be storing data using current time in "Chatlist"
        // and we are pushing data using unique id in "Chats"
        DatabaseReference databaseReference = FirebaseDatabase.getInstance().getReference();
        String timestamp = String.valueOf(System.currentTimeMillis());
        HashMap hashMap = new HashMap<>();
        hashMap.put("sender", myuid);
        hashMap.put("receiver", uid);
        hashMap.put("message", message);
        hashMap.put("timestamp", timestamp);
        hashMap.put("dilihat", false);
        hashMap.put("type", "text");
        databaseReference.child("Chats").push().setValue(hashMap);
        final DatabaseReference ref1 = FirebaseDatabase.getInstance().getReference("ChatList").child(uid).child(myuid);
        ref1.addValueEventListener(new ValueEventListener() {
            @Override
            public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
                if (!dataSnapshot.exists()) {
                    ref1.child("id").setValue(myuid);
                }
            }
  
            @Override
            public void onCancelled(@NonNull DatabaseError databaseError) {
  
            }
        });
        final DatabaseReference ref2 = FirebaseDatabase.getInstance().getReference("ChatList").child(myuid).child(uid);
        ref2.addValueEventListener(new ValueEventListener() {
            @Override
            public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
  
                if (!dataSnapshot.exists()) {
                    ref2.child("id").setValue(uid);
                }
            }
  
            @Override
            public void onCancelled(@NonNull DatabaseError databaseError) {
  
            }
        });
    }
  
    @Override
    public boolean onOptionsItemSelected(@NonNull MenuItem item) {
        if (item.getItemId() == R.id.logout) {
            firebaseAuth.signOut();
            checkUserStatus();
        }
        return super.onOptionsItemSelected(item);
    }
  
    private void checkUserStatus() {
        FirebaseUser user = firebaseAuth.getCurrentUser();
        if (user != null) {
            myuid = user.getUid();
        }
  
    }
}

输出：

在聊天列表片段中显示所有聊天

步骤1：使用ModelChatlist.xml文件

获取我们已向其发送消息的用户的ID。

Java

package com.example.socialmediaapp;
  
class ModelChatList {
  
    public String getId() {
        return id;
    }
  
    public void setId(String id) {
        this.id = id;
    }
  
    public ModelChatList() {
    }
  
    public ModelChatList(String id) {
        this.id = id;
    }
  
    String id;
}

步骤2：使用AdapterChatList。 Java文件

显示用户和聊天中发送的最后一条消息。

Java

package com.example.socialmediaapp;
  
import android.content.Context;
import android.content.Intent;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ImageView;
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.HashMap;
import java.util.List;
  
public class AdapterChatList extends RecyclerView.Adapter {
  
    Context context;
    FirebaseAuth firebaseAuth;
    String uid;
  
    public AdapterChatList(Context context, List users) {
        this.context = context;
        this.usersList = users;
        lastMessageMap = new HashMap<>();
        firebaseAuth = FirebaseAuth.getInstance();
        uid = firebaseAuth.getUid();
    }
  
    List usersList;
    private HashMap lastMessageMap;
  
    @NonNull
    @Override
    public Myholder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
        View view = LayoutInflater.from(context).inflate(R.layout.row_chatlist, parent, false);
        return new Myholder(view);
    }
  
    @Override
    public void onBindViewHolder(@NonNull Myholder holder, final int position) {
  
        final String hisuid = usersList.get(position).getUid();
        String userimage = usersList.get(position).getImage();
        String username = usersList.get(position).getName();
        String lastmess = lastMessageMap.get(hisuid);
        holder.name.setText(username);
        holder.block.setImageResource(R.drawable.ic_unblock);
         
        // if no last message then Hide the layout
        if (lastmess == null || lastmess.equals("default")) {
            holder.lastmessage.setVisibility(View.GONE);
        } else {
            holder.lastmessage.setVisibility(View.VISIBLE);
            holder.lastmessage.setText(lastmess);
        }
        try {
            // loading profile pic of user
            Glide.with(context).load(userimage).into(holder.profile);
        } catch (Exception e) {
  
        }
          
        // redirecting to chat activity on item click
        holder.itemView.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent intent = new Intent(context, ChatActivity.class);
                 
                // putting uid of user in extras
                intent.putExtra("uid", hisuid);
                context.startActivity(intent);
            }
        });
  
    }
  
    // setting last message sent by users.
    public void setlastMessageMap(String userId, String lastmessage) {
        lastMessageMap.put(userId, lastmessage);
    }
  
    @Override
    public int getItemCount() {
        return usersList.size();
    }
  
    class Myholder extends RecyclerView.ViewHolder {
        ImageView profile, status, block, seen;
        TextView name, lastmessage;
  
        public Myholder(@NonNull View itemView) {
            super(itemView);
            profile = itemView.findViewById(R.id.profileimage);
            status = itemView.findViewById(R.id.onlinestatus);
            name = itemView.findViewById(R.id.nameonline);
            lastmessage = itemView.findViewById(R.id.lastmessge);
            block = itemView.findViewById(R.id.blocking);
            seen = itemView.findViewById(R.id.seen);
        }
    }
}

步骤3：使用fragment_chatlist.xml文件

使用回收者视图显示所有用户。

步骤4：使用ChatlistFragment。 Java文件

在这里，我们显示了已向其发送消息的所有用户。这就是我们如何获取当前用户的最后一条消息。如果消息类型为图像，则只需将最后一条消息设置为“已发送照片”。

if(chat.getReceiver().equals(firebaseUser.getUid())&&
                            chat.getSender().equals(uid)||
                            chat.getReceiver().equals(uid)&&
                                    chat.getSender().equals(firebaseUser.getUid())){
                        if(chat.getType().equals("images")){
                            lastmess="Sent a Photo";
                        }
                        else {
                            lastmess = chat.getMessage();
                        }
                    }

下面是ChatlistFragment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.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 ChatListFragment extends Fragment {
  
    FirebaseAuth firebaseAuth;
    RecyclerView recyclerView;
    List chatListList;
    List usersList;
    DatabaseReference reference;
    FirebaseUser firebaseUser;
    AdapterChatList adapterChatList;
    List chatList;
  
    public ChatListFragment() {
        // 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_chat_list, container, false);
        firebaseAuth = FirebaseAuth.getInstance();
          
        // getting current user
        firebaseUser = FirebaseAuth.getInstance().getCurrentUser();
        recyclerView = view.findViewById(R.id.chatlistrecycle);
        chatListList = new ArrayList<>();
        chatList = new ArrayList<>();
        reference = FirebaseDatabase.getInstance().getReference("ChatList").child(firebaseUser.getUid());
        reference.addValueEventListener(new ValueEventListener() {
            @Override
            public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
                chatListList.clear();
                for (DataSnapshot ds : dataSnapshot.getChildren()) {
                    ModelChatList modelChatList = ds.getValue(ModelChatList.class);
                    if (!modelChatList.getId().equals(firebaseUser.getUid())) {
                        chatListList.add(modelChatList);
                    }
  
                }
                loadChats();
            }
  
            @Override
            public void onCancelled(@NonNull DatabaseError databaseError) {
  
            }
        });
        return view;
  
    }
  
    // loading the user chat layout using chat node
    private void loadChats() {
        usersList = new ArrayList<>();
        reference = FirebaseDatabase.getInstance().getReference("Users");
        reference.addValueEventListener(new ValueEventListener() {
            @Override
            public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
                usersList.clear();
                for (DataSnapshot dataSnapshot1 : dataSnapshot.getChildren()) {
                    ModelUsers user = dataSnapshot1.getValue(ModelUsers.class);
                    for (ModelChatList chatList : chatListList) {
                        if (user.getUid() != null && user.getUid().equals(chatList.getId())) {
                            usersList.add(user);
                            break;
                        }
                    }
                    adapterChatList = new AdapterChatList(getActivity(), usersList);
                    recyclerView.setAdapter(adapterChatList);
                      
                    // getting last message of the user
                    for (int i = 0; i < usersList.size(); i++) {
                        lastMessage(usersList.get(i).getUid());
                    }
                }
            }
  
            @Override
            public void onCancelled(@NonNull DatabaseError databaseError) {
  
            }
        });
    }
  
    private void lastMessage(final String uid) {
        DatabaseReference ref = FirebaseDatabase.getInstance().getReference("Chats");
        ref.addValueEventListener(new ValueEventListener() {
            @Override
            public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
                String lastmess = "default";
                for (DataSnapshot dataSnapshot1 : dataSnapshot.getChildren()) {
                    ModelChat chat = dataSnapshot1.getValue(ModelChat.class);
                    if (chat == null) {
                        continue;
                    }
                    String sender = chat.getSender();
                    String receiver = chat.getReceiver();
                    if (sender == null || receiver == null) {
                        continue;
                    }
                    // checking for the type of message if
                    // message type is image then set
                    // last message as sent a photo
                    if (chat.getReceiver().equals(firebaseUser.getUid()) &&
                            chat.getSender().equals(uid) ||
                            chat.getReceiver().equals(uid) &&
                                    chat.getSender().equals(firebaseUser.getUid())) {
                        if (chat.getType().equals("images")) {
                            lastmess = "Sent a Photo";
                        } else {
                            lastmess = chat.getMessage();
                        }
                    }
                }
                adapterChatList.setlastMessageMap(uid, lastmess);
                adapterChatList.notifyDataSetChanged();
            }
  
            @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：