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| 1. build.gradle 依赖
确保你的 app 模块的 build.gradle（通常是 app/build.gradle）包含以下依赖：
// Room 依赖 分为java和kotlin
//java的
def room_version = "2.5.2"
implementation "androidx.room:room-runtime:$room_version"
annotationProcessor "androidx.room:room-compiler:$room_version"
//kotlin必须 kapt
plugins {
alias(libs.plugins.android.application)
alias(libs.plugins.kotlin.android)
id 'kotlin-kapt'
}
implementation "androidx.room:room-runtime:$room_version"
implementation "androidx.room:room-ktx:$room_version" // 可选，支持协程
kapt "androidx.room:room-compiler:$room_version" // Kotlin 必须用 kapt
import androidx.room.Entity;
import androidx.room.PrimaryKey;
@Entity
public class User {
@PrimaryKey(autoGenerate = true)
public int userId;
public String name;
public int age;
public User(String name, int age) {
this.name = name;
this.age = age;
}
}
import androidx.room.Dao;
import androidx.room.Insert;
import androidx.room.Query;
import java.util.List;
@Dao
public interface UserDao {
@Insert
void insertUser(User user);
@Query("SELECT * FROM User")
List<User> getAllUsers();
}
import androidx.room.Database;
import androidx.room.RoomDatabase;
@Database(entities = {User.class}, version = 1)
public abstract class AppDatabase extends RoomDatabase {
public abstract UserDao userDao();
}
// 在Activity或Application里初始化
AppDatabase db = Room.databaseBuilder(getApplicationContext(),
AppDatabase.class, "my-database").build();
// 插入数据（注意不能在主线程，建议放到子线程）
new Thread(() -> {
UserDao userDao = db.userDao();
BookDao bookDao = db.bookDao();
User user = new User("Alice", 30);
userDao.insertUser(user);
Book book = new Book("Android Development", 1); // 这里1为userId，需要先获取
bookDao.insertBook(book);
List<User> users = userDao.getAllUsers();
List<Book> books = bookDao.getBooksByUserId(1);
// 处理结果
}).start();
import android.app.Application;
import androidx.room.Room;
public class MyApp extends Application {
private static AppDatabase database;
@Override
public void onCreate() {
super.onCreate();
database = Room.databaseBuilder(getApplicationContext(),
AppDatabase.class, "my-database")
.build();
}
// 对外暴露获取数据库实例的方法
public static AppDatabase getDatabase() {
return database;
}
}
其他页面调用
AppDatabase db = MyApp.getDatabase();
UserDao userDao = db.userDao();
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