Room库无法识别我为枚举列表创建的TypeConverter.但是,当我将其更改为枚举的ArrayList时,它工作正常.任何人都知道为什么以及我该怎么做才能使这个工作与List？ (在Kotlin中使用List更容易,我真的不想因为这个原因而转换回ArrayList).
这是我的代码：
我的模特：
@Entity data class Example(@PrimaryKey val id: String?,val name: String,var days: List<DayOfWeek>?)
DayOfWeek是一个枚举：
enum class DayOfWeek {
MONDAY,TUESDAY,WEDNESDAY,THURSDAY,FRIDAY,SATURDAY,SUNDAY;
val value: Int
get() = ordinal + 1
companion object {
private val ENUMS = DayOfWeek.values()
fun of(dayOfWeek: Int): DayOfWeek {
if (dayOfWeek < 1 || dayOfWeek > 7) {
throw RuntimeException("Invalid value for DayOfWeek: " + dayOfWeek)
}
return ENUMS[dayOfWeek - 1]
}
}
}
我的TypeConverter：
private const val SEPARATOR = ","
class DayOfWeekConverter {
@TypeConverter
fun daysOfWeekToString(daysOfWeek: List<DayOfWeek>?): String? {
return daysOfWeek?.map { it.value }?.joinToString(separator = SEPARATOR)
}
@TypeConverter
fun stringToDaysOfWeek(daysOfWeek: String?): List<DayOfWeek>? {
return daysOfWeek?.split(SEPARATOR)?.map { DayOfWeek.of(it.toInt()) }
}
}
我将它设置在我的DB类中,如下所示：
@Database(entities = arrayOf(Example::class),version = 1)
@TypeConverters(DayOfWeekConverter::class)
abstract class AppDatabase : RoomDatabase() {
abstract fun exampleDao(): ExampleDao
}
我的DAO看起来像这样：
@Dao
interface ExampleDao {
@Query("SELECT * FROM example")
fun getAll(): LiveData<List<Example>>
@Insert(onConflict = REPLACE)
fun save(examples: List<Example>)
}
error: Cannot figure out how to save this field into database. You can consider adding a type converter for it. e: e: private java.util.List<? extends com.example.DayOfWeek> days;
就像我上面说的,如果我将days属性更改为ArrayList< DayOfWeek> (并在DayOfWeekConverter中对ArrayList进行更改)然后一切正常.如果有人能帮我解决这个问题并告诉我如何在这里使用List它会有很大的帮助,它让我发疯：/.
解决方法
出于某种原因,Room不喜欢Kotlin List,但是当我用MutableList替换List时,它开始工作：
@Entity
data class Example(@PrimaryKey val id: String,var days: MutableList<DayOfWeek>?)
class DayOfWeekConverter {
companion object {
@TypeConverter
@JvmStatic
fun daysOfWeekToString(daysOfWeek: MutableList<DayOfWeek>?): String? =
daysOfWeek?.map { it.value }?.joinToString(separator = SEPARATOR)
@TypeConverter
@JvmStatic
fun stringToDaysOfWeek(daysOfWeek: String?): MutableList<DayOfWeek>? =
daysOfWeek?.split(SEPARATOR)?.map { DayOfWeek.of(it.toInt()) }?.toMutableList()
}
}
这不是完美的解决方案,但希望您可以通过它进行更多调查.
您还需要将@PrimaryKey更改为不可为空
