我如何在房间使用日期和时间

Question

我有下面的模型，其中包括date和time领域

import androidx.room.Entity
import androidx.room.PrimaryKey
import java.time.LocalDate
import java.time.LocalTime

@Entity
data class Assignment(
    @PrimaryKey(autoGenerate = true) val tid: Int,

   // @PrimaryKey val uid: Int,
    @ColumnInfo(name = "id") val id: Int,
    @ColumnInfo(name = "task") val task: String?,
    @ColumnInfo(name = "address") val address: String?,
    @ColumnInfo(name = "datePicker") val datePicker: LocalDate?,
    @ColumnInfo(name = "timePicker") val timePicker: LocalTime?,
    @ColumnInfo(name = "status") val status: String?
)

但我收到以下错误：

无法弄清楚如何将此字段保存到数据库中。您可以考虑为其添加类型转换器。

所以，我写了下面的转换器：

import java.sql.Date
import java.time.LocalDate
import javax.persistence.AttributeConverter
import javax.persistence.Converter
import java.time.ZoneId.systemDefault

@Converter(autoApply = true)
class LocalDateAttributeConverter : AttributeConverter<LocalDate, Date> {

    override fun convertToDatabaseColumn(locDate: LocalDate?): Date? {
        return if (locDate == null) null else Date.valueOf(locDate.toString())
    }

    override fun convertToEntityAttribute(sqlDate: Date?): LocalDate? {
        val defaultZoneId = systemDefault()
        val instant = sqlDate?.toInstant()
        return instant?.atZone(defaultZoneId)?.toLocalDate()
    }
}

但是不知道怎么用这个convertor配合数据库model？

更新 根据收到的答案，我将代码更改为如下所示，但仍然出现相同的错误：

转换器：

import androidx.room.TypeConverter
import java.sql.Date
import java.time.LocalDate
import java.time.ZoneId.systemDefault

class Converters {
    @TypeConverter
    fun convertToDatabaseColumn(locDate: LocalDate?): Date? {
        return locDate?.let { Date.valueOf(locDate.toString()) }
    }

    @TypeConverter
    fun convertToEntityAttribute(sqlDate: Date?): LocalDate? {
        val defaultZoneId = systemDefault()
        val instant = sqlDate?.toInstant()
        return instant?.atZone(defaultZoneId)?.toLocalDate()
    }
}

数据库：

import android.content.Context
import androidx.room.Database
import androidx.room.Room
import androidx.room.RoomDatabase
import androidx.room.TypeConverters
import kotlinx.coroutines.CoroutineScope

@Database(entities = [Assignment::class], version = 1)
@TypeConverters(Converters::class)
abstract class AppDatabase : RoomDatabase() {
    abstract fun assignmentDao(): AssignmentDao

    companion object {
        @Volatile
        var INSTANCE: AppDatabase? = null

        fun getDatabase(context: Context,
                        scope: CoroutineScope
        ): AppDatabase {
            val tempInstance = INSTANCE
            if (tempInstance != null) {
                return tempInstance
            }
            synchronized(this) {
                val instance = Room.databaseBuilder(
                    context.applicationContext,
                    AppDatabase::class.java,
                    "database-name"
                ).addCallback(AppDatabaseCallback(scope))
                    .build()
                INSTANCE = instance
                return instance
            }
        }
    }
}

和

import androidx.room.ColumnInfo
import androidx.room.Entity
import androidx.room.PrimaryKey
import androidx.room.TypeConverters
import java.time.LocalDate
import java.time.LocalTime
//import javax.persistence.Convert

@Entity
data class Assignment(
    @PrimaryKey(autoGenerate = true) val tid: Int,

   // @PrimaryKey val uid: Int,
    @ColumnInfo(name = "id") val id: Int,
    @ColumnInfo(name = "task") val task: String?,
    @ColumnInfo(name = "address") val address: String?,
    @ColumnInfo(name = "timePicker") val timePicker: LocalTime?,
    @ColumnInfo(name = "status") val status: String?,

    @TypeConverters(Converters::class)
    @ColumnInfo(name = "datePicker") val datePicker: LocalDate?
)

Answer 1

long time = new Date().getTime();
long sysTime = System.currentTimeMillis();

以上两者都将返回相同的长型值。所以，你可以只使用其中之一。甚至可以像这样转换为小时、分钟或秒（这在分配值时很有用）：

int hours = (int) TimeUnit.MILLISECONDS.toHours(System.currentTimeMillis());
int minutes = (int) TimeUnit.MILLISECONDS.toMinutes(System.currentTimeMillis());
int seconds = (int) TimeUnit.MILLISECONDS.toSeconds(System.currentTimeMillis());

int date = new Date().getDate();
String formatedDate = new SimpleDateFormat("dd-MM-yyyy").format(new Date());

在这里，date 将返回值作为 int（今天为 3），formatedDate 将返回值作为 String（今天为 03-08-2019）。

所以，你可以在你的房间数据库类中做什么，为时间声明 long 类型变量，为日期声明 int/String（你喜欢的）。然后，在为这些变量赋值时，请使用上述技术。

在 Kotlin 中可以这样做：

button.setOnClickListener {
       val formatedDate = SimpleDateFormat("yyyy-MM-dd").format(Date())
       val formatedTime = SimpleDateFormat("HH:mm").format(Date())
       val DateTime = "$formatedDate  $formatedTime"
       appViewModel.updateLastUpdateById(this, task_id, DateTime)
}

在模型/房间中，如：

@Entity
data class Assignment(
    @ColumnInfo(name = "lastUpdate") val lastUpdate: String?
)