DeviceDatabase

package tw.guodong.remotecontrol.database

import android.arch.persistence.room.Database
import android.arch.persistence.room.RoomDatabase
import tw.guodong.remotecontrol.pojo.DeviceInfo
import tw.guodong.remotecontrol.pojo.dao.DeviceInfoDao

/**
 * Created by tony on 2018/1/11.
 */
@Database(entities = arrayOf(DeviceInfo::class), version = 1)
abstract class DeviceDatabase : RoomDatabase() {

    abstract fun deviceDao(): DeviceInfoDao

}

DeviceInfo

package tw.guodong.remotecontrol.pojo

import android.arch.persistence.room.Entity
import android.arch.persistence.room.PrimaryKey
import android.arch.persistence.room.ColumnInfo
import android.text.TextUtils

/**
 * Created by tony on 2018/1/10.
 */
@Entity
data class DeviceInfo(
        @PrimaryKey()
        val id: String,
        @ColumnInfo(name = "name")
        var name: String = id,
        @ColumnInfo(name = "push_token")
        var pushToken: String = "") {

    init {
        if(TextUtils.isEmpty(name)) name = id
    }

}

DeviceInfoDao

package tw.guodong.remotecontrol.pojo.dao

import android.arch.persistence.room.Dao
import android.arch.persistence.room.Insert
import android.arch.persistence.room.Query
import tw.guodong.remotecontrol.pojo.DeviceInfo




/**
 * Created by tony on 2018/1/11.
 */
@Dao
interface DeviceInfoDao {

    @Query("IF EXISTS(SELECT * FROM device WHERE id = :deviceId)")
    fun isDeviceExist(deviceId: String): Boolean

    @Query("SELECT * FROM device WHERE id = :deviceId LIMIT 1")
    fun getDeviceInfo(deviceId: String): DeviceInfo

    @Insert
    fun insertDeviceInfo(deviceInfo: DeviceInfo)
}

example

val deviceDatabase: DeviceDatabase = Room.databaseBuilder(MyApplication.maperApplicationContext, DeviceDatabase::class.java, "device").build()
            val deviceDao = deviceDatabase.deviceDao()
            val deviceId = getDeviceId(MyApplication.maperApplicationContext)
            val isDeviceExist = deviceDao.isDeviceExist(deviceId)
            val deviceInfo = if(isDeviceExist) {
                deviceDao.getDeviceInfo(deviceId)
            } else {
                val tmpDeviceInfo = DeviceInfo(getDeviceId(MyApplication.maperApplicationContext))
                deviceDao.insertDeviceInfo(tmpDeviceInfo)
                tmpDeviceInfo
            }
            Log.v("guodong", "deviceInfo: $deviceInfo")