1，引入依赖

plugins {id 'kotlin-kapt'
}

dependencies {implementation "androidx.room:room-runtime:2.4.2"kapt "androidx.room:room-compiler:2.4.2"
}

 2，标记实体类

import androidx.room.Entity
import androidx.room.PrimaryKey@Entity(tableName = "banner")
data class Banner(val desc: String,@PrimaryKeyval id: Int,val imagePath: String,val isVisible: Int,val order: Int,val title: String,val type: Int,val url: String
)

3，对应的Dao类

 

import androidx.room.Dao
import androidx.room.Delete
import androidx.room.Insert
import androidx.room.OnConflictStrategy
import androidx.room.Query
import androidx.room.Update@Dao
interface BannerDao {@get:Query("SELECT * FROM banner")val getBanners: List<Banner>@Query("SELECT * FROM banner WHERE 'id' = :userId")fun getBannerById(userId: Int): Banner?@Query("SELECT * FROM banner WHERE 'id' IN (:userIds)")fun getBannersByIds(userIds: IntArray): List<Banner>@Insert(onConflict = OnConflictStrategy.REPLACE) //重复时则会替换。fun insert(vararg user: Banner)@Deletefun delete(vararg user: Banner)@Updatefun update(vararg user: Banner)@Query("DELETE FROM banner")fun deleteAll()@Query("SELECT COUNT(*) FROM banner")fun countAll():Int
}

4，RoomDatabase类

import androidx.room.Database
import androidx.room.RoomDatabase@Database(entities = [Banner::class], version = 1,exportSchema = false)
abstract class MyDatabase:RoomDatabase() {abstract fun bannerDao():BannerDao
}

5，工具类

import android.content.Context
import androidx.room.Roomclass DatabaseUtil private constructor(context: Context) {//双重检测单例companion object {@Volatileprivate var databaseUtil: DatabaseUtil? = nullfun getInstance(context: Context): DatabaseUtil {if (databaseUtil == null) {synchronized(DatabaseUtil::class) {if (databaseUtil == null) {databaseUtil = DatabaseUtil(context)}}}return databaseUtil!!}}val myDatabase: MyDatabaseinit {myDatabase = Room.databaseBuilder(context, MyDatabase::class.java, "my_database").allowMainThreadQueries().build()}
}