Architecture -- Room

1). 简介

Room persistence库为SQLite提供了一个抽象层，以便在利用SQLite的全部功能的同时实现更强大的数据库访问。
该库可帮助您在运行应用程序的设备上创建应用程序数据的缓存。 此缓存作为应用程序的唯一事实来源，允许用户在应用程序中查看关键信息的一致副本，无论用户是否具有Internet连接。

2). 依赖

buildscript {
  ext.room_version = "1.1.0"
}

dependencies {
  // Room 使用
  implementation "android.arch.persistence.room:runtime:$room_version"
  annotationProcessor "android.arch.persistence.room:compiler:$room_version"
  // optional - RxJava support for Room
  implementation "android.arch.persistence.room:rxjava2:$room_version"
  // optional - Guava support for Room, including Optional and ListenableFuture
  implementation "android.arch.persistence.room:guava:$room_version"
  // Test helpers
  testImplementation "android.arch.persistence.room:testing:$room_version"
  // Kotlin
  kapt "android.arch.persistence.room:compiler:$room_version"
}

3). 数据实体类

 * 实体类
 * Created by mazaiting on 2018/7/25.
 */
@Entity
data class User(
       @PrimaryKey
        val uid: Int,
       @ColumnInfo(name = "first_name")
       var firstName: String,
       @ColumnInfo(name = "last_name")
       var lastName: String
)

4). 用户DAO类

/**
 * 用户DAO类
 * Created by mazaiting on 2018/7/25.
 */
@Dao
interface UserDao {
  @Query("SELECT * FROM user")
  fun getAll(): List
  @Query("SELECT * FROM user  WHERE uid IN (:userIds)")
  fun loadAllByIds(userIds: IntArray): List
  @Query("SELECT * FROM user WHERE first_name LIKE :first AND last_name LIKE :last LIMIT 1")
  fun findByName(first: String, last: String): User
  @Insert
  fun insertAll(users: List)
  // 可变参数
//  fun insertAll(vararg users: User)
  @Delete
  fun delete(user: User)
  @Update
  fun update(user: User)
}

5). 数据库类

/**
 * 数据库类
 * Created by mazaiting on 2018/7/25.
 */
@Database(entities = arrayOf(User::class), version = 1)
abstract class AppDatabase : RoomDatabase() {
  // 获取DAO
  abstract fun userDao(): UserDao
}

6). 创建数据库

    btn_create_db.setOnClickListener {
      val db = Room.databaseBuilder(applicationContext, AppDatabase::class.java, "TEST").build()
      userDao = db.userDao()
    }

7). 新增数据

对数据的操作必须在子线程中

    btn_insert.setOnClickListener {
      Thread(Runnable {
        val users = (0..10).map { User(it, "first$it", "last$it") }
        userDao.insertAll(users)
      }).start()
    }

8). 查询数据

    btn_find_all.setOnClickListener {
      Thread(Runnable {
        userDao.getAll().forEach { L.e(it.toString()) }
      }).start()
    }
    btn_find_id.setOnClickListener {
      Thread(Runnable {
        userDao.loadAllByIds(intArrayOf(0, 1, 2, 3, 4)).forEach { L.e(it.toString()) }
      }).start()
    }
    btn_find_name.setOnClickListener {
      Thread(Runnable {
        L.e(userDao.findByName("first1", "last1").toString())
      }).start()
    }

9). 更新数据

    btn_update.setOnClickListener {
      Thread(Runnable {
        val user = userDao.findByName("first1", "last1")
        user.firstName = "ma"
        user.lastName = "zaiting"
        userDao.update(user)
        userDao.loadAllByIds(intArrayOf(1)).forEach { L.e(it.toString()) }
      }).start()
    }

10). 删除数据

    btn_delete.setOnClickListener {
      Thread(Runnable {
        userDao.delete(userDao.loadAllByIds(intArrayOf(0))[0])
      }).start()
    }

11). 原文地址

12). 代码下载