Android studio消息同步机制：消息本地存储，服务器交互减压

消息同步机制:
手机端可以将消息存储在本地数据库中，减少与服务器的交互压力。同时，通过序列号机制，手机端可以与服务器同步消息，确保消息列表的一致性。

我们将使用 SQLite 数据库 在手机端存储消息，并通过 序列号机制 实现消息的同步。

后端（Flask）代码

我们为每条消息添加一个序列号字段，并在发送消息时返回当前的最大序列号。

from flask import Flask, request, jsonify
from flask_sqlalchemy import SQLAlchemy
from flask_socketio import SocketIO, emit
import uuidapp = Flask(__name__)
app.config['SQLALCHEMY_DATABASE_URI'] = 'sqlite:///messages.db'
app.config['SQLALCHEMY_TRACK_MODIFICATIONS'] = False
db = SQLAlchemy(app)
socketio = SocketIO(app)# 数据库模型
class Message(db.Model):id = db.Column(db.String(36), primary_key=True)  # 使用 UUID 作为唯一标识sender = db.Column(db.String(50), nullable=False)content = db.Column(db.String(255), nullable=False)timestamp = db.Column(db.DateTime, server_default=db.func.now())sequence = db.Column(db.Integer, unique=True, nullable=False)  # 添加序列号字段# 初始化序列号
current_sequence = 0@app.route('/send_message', methods=['POST'])
def send_message():global current_sequencedata = request.jsonsender = data['sender']content = data['content']message_id = str(uuid.uuid4())  # 生成唯一标识# 更新序列号current_sequence += 1new_message = Message(id=message_id, sender=sender, content=content, sequence=current_sequence)db.session.add(new_message)db.session.commit()# 通过 WebSocket 发送消息到所有客户端socketio.emit('new_message', {'id': message_id, 'sender': sender, 'content': content, 'sequence': current_sequence})return jsonify({'status': 'success', 'message_id': message_id, 'sequence': current_sequence})@app.route('/get_messages', methods=['GET'])
def get_messages():last_sequence = request.args.get('last_sequence', type=int, default=0)messages = Message.query.filter(Message.sequence > last_sequence).all()result = []for message in messages:result.append({'id': message.id,'sender': message.sender,'content': message.content,'timestamp': message.timestamp,'sequence': message.sequence})return jsonify(result)if __name__ == '__main__':db.create_all()  # 创建数据库和表socketio.run(app, debug=True)

前端（Android Studio Java）代码

在手机端使用 SQLite 数据库存储消息，并通过序列号机制同步消息。

1. 添加 SQLite 数据库支持
   在 build.gradle 文件中添加 SQLite 依赖：

   implementation 'androidx.sqlite:sqlite:2.3.1'
   implementation 'com.squareup.okhttp3:okhttp:4.9.3'
   implementation 'com.squareup.retrofit2:retrofit:2.9.0'
   implementation 'com.squareup.retrofit2:converter-gson:2.9.0'
   implementation 'org.java-websocket:Java-WebSocket:1.5.2'
   

2. 创建 SQLite 数据库和表
   创建一个 MessageDatabaseHelper 类来管理数据库和表。

   import android.content.Context;
   import android.database.sqlite.SQLiteDatabase;
   import android.database.sqlite.SQLiteOpenHelper;public class MessageDatabaseHelper extends SQLiteOpenHelper {private static final String DATABASE_NAME = "messages.db";private static final int DATABASE_VERSION = 1;private static final String TABLE_MESSAGES = "messages";private static final String COLUMN_ID = "id";private static final String COLUMN_SENDER = "sender";private static final String COLUMN_CONTENT = "content";private static final String COLUMN_SEQUENCE = "sequence";public MessageDatabaseHelper(Context context) {super(context, DATABASE_NAME, null, DATABASE_VERSION);}@Overridepublic void onCreate(SQLiteDatabase db) {String CREATE_TABLE = "CREATE TABLE " + TABLE_MESSAGES + "("+ COLUMN_ID + " TEXT PRIMARY KEY, "+ COLUMN_SENDER + " TEXT, "+ COLUMN_CONTENT + " TEXT, "+ COLUMN_SEQUENCE + " INTEGER)";db.execSQL(CREATE_TABLE);}@Overridepublic void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {db.execSQL("DROP TABLE IF EXISTS " + TABLE_MESSAGES);onCreate(db);}
   }
   

3. MainActivity
   在 MainActivity 中添加消息存储和同步逻辑。

   import android.database.Cursor;
   import android.database.sqlite.SQLiteDatabase;
   import android.os.Bundle;
   import android.view.View;
   import android.widget.ArrayAdapter;
   import android.widget.Button;
   import android.widget.EditText;
   import android.widget.ListView;
   import androidx.appcompat.app.AppCompatActivity;
   import okhttp3.*;
   import org.java_websocket.client.WebSocketClient;
   import org.java_websocket.handshake.ServerHandshake;
   import java.net.URI;
   import java.util.ArrayList;public class MainActivity extends AppCompatActivity {private EditText messageInput;private Button sendButton;private ListView messageList;private ArrayAdapter<String> adapter;private ArrayList<String> messages = new ArrayList<>();private WebSocketClient webSocketClient;private MessageDatabaseHelper dbHelper;private SQLiteDatabase db;private int lastSequence = 0;@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);messageInput = findViewById(R.id.messageInput);sendButton = findViewById(R.id.sendButton);messageList = findViewById(R.id.messageList);adapter = new ArrayAdapter<>(this, android.R.layout.simple_list_item_1, messages);messageList.setAdapter(adapter);dbHelper = new MessageDatabaseHelper(this);db = dbHelper.getWritableDatabase();sendButton.setOnClickListener(new View.OnClickListener() {@Overridepublic void onClick(View v) {sendMessage();}});connectWebSocket();loadMessagesFromDatabase();}private void sendMessage() {String message = messageInput.getText().toString();if (!message.isEmpty()) {// 发送消息到后端OkHttpClient client = new OkHttpClient();RequestBody body = new FormBody.Builder().add("sender", "User").add("content", message).build();Request request = new Request.Builder().url("http://192.168.1.2:5000/send_message") // 替换为你的后端地址.post(body).build();client.newCall(request).enqueue(new Callback() {@Overridepublic void onFailure(Call call, IOException e) {e.printStackTrace();}@Overridepublic void onResponse(Call call, Response response) throws IOException {if (response.isSuccessful()) {runOnUiThread(new Runnable() {@Overridepublic void run() {messages.add("Me: " + message);adapter.notifyDataSetChanged();messageInput.setText("");saveMessageToDatabase("User", message, lastSequence + 1);}});}}});}}private void connectWebSocket() {webSocketClient = new WebSocketClient(URI.create("ws://192.168.1.2:5000/")) {@Overridepublic void onOpen(ServerHandshake handshakedata) {runOnUiThread(new Runnable() {@Overridepublic void run() {messages.add("Connected to server");adapter.notifyDataSetChanged();}});}@Overridepublic void onMessage(String message) {runOnUiThread(new Runnable() {@Overridepublic void run() {messages.add("Server: " + message);adapter.notifyDataSetChanged();saveMessageToDatabase("Server", message, lastSequence + 1);}});}@Overridepublic void onClose(int code, String reason, boolean remote) {runOnUiThread(new Runnable() {@Overridepublic void run() {messages.add("Disconnected from server");adapter.notifyDataSetChanged();}});}@Overridepublic void onError(Exception ex) {ex.printStackTrace();}};webSocketClient.connect();}private void saveMessageToDatabase(String sender, String content, int sequence) {ContentValues values = new ContentValues();values.put(MessageDatabaseHelper.COLUMN_ID, UUID.randomUUID().toString());values.put(MessageDatabaseHelper.COLUMN_SENDER, sender);values.put(MessageDatabaseHelper.COLUMN_CONTENT, content);values.put(MessageDatabaseHelper.COLUMN_SEQUENCE, sequence);db.insert(MessageDatabaseHelper.TABLE_MESSAGES, null, values);}private void loadMessagesFromDatabase() {Cursor cursor = db.query(MessageDatabaseHelper.TABLE_MESSAGES, null, null, null, null, null, null);while (cursor.moveToNext()) {String sender = cursor.getString(cursor.getColumnIndexOrThrow(MessageDatabaseHelper.COLUMN_SENDER));String content = cursor.getString(cursor.getColumnIndexOrThrow(MessageDatabaseHelper.COLUMN_CONTENT));int sequence = cursor.getInt(cursor.getColumnIndexOrThrow(MessageDatabaseHelper.COLUMN_SEQUENCE));messages.add(sender + ": " + content);if (sequence > lastSequence) {lastSequence = sequence;}}cursor.close();adapter.notifyDataSetChanged();}@Overrideprotected void onDestroy() {super.onDestroy();if (webSocketClient != null) {webSocketClient.close();}db.close();}
   }
   

4. 设计布局

在 res/layout/activity_main.xml 中设计界面，包含输入框、发送按钮和显示消息的列表。

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"android:layout_width="match_parent"android:layout_height="match_parent"android:orientation="vertical"><EditTextandroid:id="@+id/messageInput"android:layout_width="match_parent"android:layout_height="wrap_content"android:hint="Enter message" /><Buttonandroid:id="@+id/sendButton"android:layout_width="match_parent"android:layout_height="wrap_content"android:text="Send" /><ListViewandroid:id="@+id/messageList"android:layout_width="match_parent"android:layout_height="0dp"android:layout_weight="1" />
</LinearLayout>