dependencies {
def room_version = "2.3.0"
implementation "androidx.room:room-runtime:$room_version"
kapt "androidx.room:room-compiler:$room_version"
}
在app
的build.gradle
文件中,删除以上依赖。
app
的build.gradle
文件中添加以下依赖:def room_version = "2.3.0"
implementation "androidx.room:room-ktx:$room_version"
annotationProcessor "androidx.room:room-compiler:$room_version"
android {
...
defaultConfig {
...
javaCompileOptions {
annotationProcessorOptions {
arguments = ["room.schemaLocation": "$projectDir/schemas".toString()]
}
}
}
}
以上代码使用Room的最新版本,还配置了数据表的位置。schemaLocation
是关键字, 它必须被设置为正在创建的Room Database实例将保存其清单的位置。
@Database(entities = [User::class], version = 1)
abstract class AppDatabase : RoomDatabase() {
abstract fun userDao(): UserDao
companion object {
@Volatile
private var INSTANCE: AppDatabase? = null
fun getDatabase(context: Context): AppDatabase {
val tempInstance = INSTANCE
if (tempInstance != null) {
return tempInstance
}
synchronized(this) {
val instance = Room.databaseBuilder(
context.applicationContext,
AppDatabase::class.java,
"user_database"
).build()
INSTANCE = instance
return instance
}
}
}
}
val db = AppDatabase.getDatabase(context)
val userDao = db.userDao()
val users = userDao.getAllUsers()
以上代码都需要在Room的最新版本上进行,这样,Room就可以在Android Studio上正常使用了。