如果在Room数据库中直接存储BigDecimal是无法存储的,Date类型的数据同样如此,会报以下错误
@Entity(foreignKeys = [ForeignKey(entity = RecordType::class, parentColumns = ["id"], childColumns = ["record_type_id"])], indices = [Index(value = ["record_type_id", "time", "money", "create_time"])])
open class Record : Serializable {
@PrimaryKey(autoGenerate = true)
var id = 0
var money: BigDecimal? = null
var remark: String? = null
var time: Date? = null
@ColumnInfo(name = "create_time")
var createTime: Date? = null
@ColumnInfo(name = "record_type_id")
var recordTypeId = 0
}
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既然无法直接存储,那有其他办法解决吗?当然有了,利用TypeConverters �|� Android Developers注解就可以处理
解决思路:利用TypeConverters将BigDecimal转换为Long数据存储,取数据时再将Long类型的数据转换为BigDecimal使用
1.在room中，我们主要可以通过@TypeCoventer注解来实现一个类型转换器。
object Converters {
@TypeConverter
fun fromTimestamp(value: Long?): Date? {
return if (value == null) null else Date(value)
}
@TypeConverter
fun dateToTimestamp(date: Date?): Long? {
return date?.time
}
@TypeConverter
fun stringToBig(intDecimal: Int): BigDecimal {
return BigDecimal(intDecimal)
}
@TypeConverter
fun bigToString(bigDecimal: BigDecimal): Int {
return bigDecimal.toInt()
}
}
2.在实现类型转换器之后，在表中引入这个转换器即可,也可以直接加在RoomDatabase这个类上,不用每个实体类都加一次,这样就可以实现自动转换了
@Database(entities = [Inspiration::class, Daiban::class, SportClass::class, SportLog::class, Record::class, RecordType::class], version = 4, autoMigrations = [
AutoMigration(from = 1, to = 2),
AutoMigration(from = 2, to = 3),
AutoMigration(from = 3, to = 4),
])
@TypeConverters(Converters::class)
abstract class AppDataBase : RoomDatabase() {
}
