ROOM

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| 字数统计: 445

不使用AndroidX的依赖

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def room_version = "1.1.1"

    implementation "android.arch.persistence.room:runtime:$room_version"
    kapt "android.arch.persistence.room:compiler:$room_version" // use kapt for Kotlin
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@Entity
data class User(
        @PrimaryKey val uid: Int,
        @ColumnInfo(name = "first_name") val firstName: String?,
        @ColumnInfo(name = "last_name") val lastName: String?)
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@Database(entities = [User::class], version = 1)
abstract class AppDatabase : RoomDatabase() {
    abstract fun userDao(): UserDao
}
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@Dao
interface UserDao {
    @Query("SELECT * FROM user")
    fun getAll(): List<User>

    @Query("SELECT * FROM user WHERE uid IN (:userIds)")
    fun loadAllByIds(userIds: IntArray): List<User>

    @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(vararg users: User)

    @Delete
    fun delete(user: User)

    @Query("select max(uid) from user ")
    fun queryMaxId(): Int
}
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val userDao: UserDao by lazy {
           Room.databaseBuilder(
                   appContext,
                   AppDatabase::class.java, "database-name"
           ).build().userDao()
       }

监控数据变化

使用RoomDatabase.getInvalidationTracker获取InvalidationTracker对象来监听表数据的改变。一般推荐直接在DAO方法中返回LiveData或者Observable对象。

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@Query("SELECT * FROM ConsumeInfo where timeStr LIKE :month ORDER BY time ASC")
  fun getDataWithMonth(month: String): LiveData<List<ConsumeInfo>>
  
  ViewModel中监听，也可以放在界面上监听，下面的代码只能在Model中监听
  
   val liveLists = DaoUtil.instance.getConsumeInfoList(month)
          // 添加数据监听，当数据变化时自动更新数据
          liveLists.observe(owner, Observer<List<ConsumeInfo>> {
              Logger.e("getHistoryConsume observe change")
              getAverageConsume(it)
          })
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private val users: MutableLiveData<List<User>> by lazy {
       MutableLiveData<List<User>>().also {
           uiScope.launch {
               val rst = async(Dispatchers.IO) { App.userDao.getAll() }
               it.value = rst.await()
           }
       }
   }

   fun getUsers(): LiveData<List<User>> {
       uiScope.launch {
           val rst = async(Dispatchers.IO) { App.userDao.getAll() }
           users.value = rst.await()
       }
       return users
   }


   fun setUsers() {
       uiScope.launch {
           val rst = async(Dispatchers.IO) {
               var count = App.userDao.queryMaxId()
               App.userDao.insertAll(User(++count, "f$count", "l$count"))
               App.userDao.getAll()
           }
           users.value = rst.await()
       }
   }