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我怎样才能让科特林的这首单曲更简单呢?

android-room kotlin android

s-hunter · 技术社区 · 8 年前

对于Android Room数据库初始化,我如何使Kotlin中的singleton更简单?

@Database(entities = arrayOf(Book::class, User::class), version = 1)
abstract class AppDatabase : RoomDatabase() {

    abstract fun bookModel() : BookDao
    abstract fun userModel() : UserDao

    companion object {
        private var INSTANCE: AppDatabase? = null

        fun getInMemoryDatabase(context: Context): AppDatabase {
            if (INSTANCE == null) {
                INSTANCE = Room.inMemoryDatabaseBuilder(context.applicationContext, AppDatabase::class.java).build()
            }
            return INSTANCE!!
        }

        fun destroyInstance() {
            INSTANCE = null
        }
    }
}

3 回复 | 直到 8 年前

Willi Mentzel user670265 8 年前

[] arrayOf here

@Database(entities = [Book::class, User::class], version = 1)
abstract class AppDatabase : RoomDatabase() {

    abstract fun bookModel() : BookDao
    abstract fun userModel() : UserDao

    companion object {
        private var INSTANCE: AppDatabase? = null

        fun getInMemoryDatabase(context: Context) { 
            INSTANCE = INSTANCE ?: Room.inMemoryDatabaseBuilder(context.applicationContext, AppDatabase::class.java).build()
            return INSTANCE!!
        }

        fun destroyInstance() {
            INSTANCE = null
        }
    }
}

companion object

AppDatabase

object AppDatabaseProvider {
    private var INSTANCE: AppDatabase? = null

    fun getInMemoryDatabase(context: Context) {
       // ...
    }

    fun destroyInstance() {
        INSTANCE = null
    }
}

zsmb13 8 年前

private var INSTANCE: AppDatabase? = null

fun getInMemoryDatabase(context: Context) = INSTANCE ?: Room.inMemoryDatabaseBuilder(context.applicationContext, AppDatabase::class.java).build()

getInMemoryDatabase INSTANCE null

fun getInMemoryDatabase(context: Context): AppDatabase {
    INSTANCE = INSTANCE ?: Room.inMemoryDatabaseBuilder(context.applicationContext, AppDatabase::class.java).build()
    return INSTANCE!!
}

Abner Escócio 8 年前

@Database(entities = arrayOf(Book::class, User::class), version = 1)
abstract class AppDatabase : RoomDatabase() {

    abstract fun bookModel() : BookDao
    abstract fun userModel() : UserDao

    companion object {
        private var INSTANCE: AppDatabase? = null

        fun getInMemoryDatabase(context: Context): AppDatabase {
            return INSTANCE :? Room.inMemoryDatabaseBuilder(context, this).build()
        }

        fun destroyInstance() {
            INSTANCE = null
        }
    }
}

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