Room Using Date field

Question

I am using date converter class to convert my date object. However, I still encounter an error saying. error: Cannot figure out how to save this field into a database. You can consider adding a type converter for it.

My Date Converter class

public class DateConverter {

    @TypeConverter
    public static Date toDate(Long dateLong){
        return dateLong == null ? null: new Date(dateLong);
    }

    @TypeConverter
    public static long fromDate(Date date){
        return date == null ? null :date.getTime();
    }
}

My Database table for using the date object.

@Entity(tableName = "userFitnessDailyRecords")

    @TypeConverters(DateConverter.class)
    public class UserFitnessDailyRecords {

        @NonNull
        @PrimaryKey(autoGenerate = true)
        public int id;
        public Date forDay;

        public Date getForDay() {
            return forDay;
        }

        public void setForDay(Date forDay) {
            this.forDay = forDay;
        }
    }

I followed the example from google code persistence labs and from commonwares room respective GitHub example. I am using room version 1.0.0.

For me the best way is to use Gson() to convert it into string and vice versa. You can use any type of object with Gson conversion. — abdul rehman, May 20 '20 at 17:41

score 55 · Accepted Answer · answered May 13 '18 at 12:13

You're converting from Date to Long (wrapper) and from long (primitive) to Date. I changed it to Long and it compiled. Besides, unboxing null in your converter produces a NPE.

public class DateConverter {

    @TypeConverter
    public static Date toDate(Long dateLong){
        return dateLong == null ? null: new Date(dateLong);
    }

    @TypeConverter
    public static Long fromDate(Date date){
        return date == null ? null : date.getTime();
    }
}

score 21 · Answer 2 · answered Oct 06 '19 at 17:32

See my complete example.

Refer to the documentation : https://developer.android.com/training/data-storage/room/referencing-data

public class Converters {
    @TypeConverter
    public static Date fromTimestamp(Long value) {
        return value == null ? null : new Date(value);
    }

    @TypeConverter
    public static Long dateToTimestamp(Date date) {
        return date == null ? null : date.getTime();
    }
}

Then map it to the database.

@Database(entities = {User.class}, version = 1)
@TypeConverters({Converters.class})
public abstract class AppDatabase extends RoomDatabase {
    public abstract UserDao userDao();
}

And the entity.

@Entity
public class User {
    private Date birthday;
}

if we make the inner element as a list how do we do it? https://stackoverflow.com/questions/70815892/what-should-we-do-for-nested-objects-in-room — , Jan 23 '22 at 10:09

score 10 · Answer 3 · answered Dec 26 '21 at 14:23

Date TypeConverter for Kotlin:

class Converters {
  @TypeConverter
  fun fromTimestamp(value: Long?): Date? {
    return value?.let { Date(it) }
  }

  @TypeConverter
  fun dateToTimestamp(date: Date?): Long? {
    return date?.time?.toLong()
  }
}

and here is how to attach it to your database:

@Database(entities = [User::class], version = 1)
@TypeConverters(Converters::class)
abstract class AppDatabase : RoomDatabase() {
  abstract fun userDao(): UserDao
}

Copied from official docs

O-9 · Answer 4 · 2020-06-06T21:41:11.613

I had this same problem (how to store time to Room), but I was using Calendar, so I made this: [note: This anwer is for Calendar ; the main reason is that Calendar is now supported]

edit: the main reason for this answer is that Date is deprecated, so here you go

  @TypeConverter
  public static Calendar toCalendar(Long l) {
    Calendar c = Calendar.getInstance();
    c.setTimeInMillis(l);
    return c;
  }

  @TypeConverter
  public static Long fromCalendar(Calendar c){
    return c == null ? null : c.getTime().getTime();
  }

score 7 · Answer 5 · edited Mar 17 '19 at 09:13

7

Put converter class in class of data base, not in the model :

@Database(entities = {
    Patient.class,Medicine.class,Tooth.class,})

@TypeConverters({TimeConverter.class,OutBoundConverter.class})

public abstract class PatientDataBase extends RoomDatabase {//your data base}

edited Mar 17 '19 at 09:13

Fukiyel

1,166
7
19

answered Mar 17 '19 at 07:13

Hassan Hallak

321
3
6

score 4 · Answer 6 · answered Nov 04 '20 at 04:35

If you don't want to deal with Autoboxing and Unboxing, just use the primitive long data type as below:

public class DateConverter {

  @TypeConverter
  public static Date toDate(long date) {
    return new Date(date);
  }

  @TypeConverter
  public static long fromDate(Date date) {
    return date == null ? Calendar.getInstance().getTimeInMillis() : date.getTime();
  }
}

Note that this will default the date to current date.

score 2 · Answer 7 · answered Aug 31 '19 at 08:49

Using Calendar with Kotlin (adapted from O95's answer):

@TypeConverter
fun toCalendar(l: Long?): Calendar? =
    if (l == null) null else Calendar.getInstance().apply { timeInMillis = l }

@TypeConverter
fun fromCalendar(c: Calendar?): Long? = c?.time?.time

score 2 · Answer 8 · answered Nov 20 '19 at 12:16

2

You can write it on Kotlin as well

@TypeConverter
fun toDate(dateLong:Long):Date {
    return Date(dateLong)
}

@TypeConverter
fun fromDate(date: Date):Long{
    return date.time;
}

answered Nov 20 '19 at 12:16

Potehin Ruslan

51
4

score 2 · Answer 9 · answered Mar 12 '20 at 10:50

AndroidThreeTen is the port of Java8 new time classes, which unfortunately are available only for api>=26. Using https://github.com/JakeWharton/ThreeTenABP , we can use LocalDateTime on all versions of Android. Here in kotlin the converter,

class Converters {
    @TypeConverter
    fun fromTimestamp(value: Long?): LocalDateTime? {
        return value?.let {
            LocalDateTime.ofInstant(
                Instant.ofEpochMilli(it), ZoneId.systemDefault()
            )
        }
    }

    @TypeConverter
    fun LocalDateTimeToTimestamp(date: LocalDateTime?): Long? {
        return date?.atZone(ZoneId.systemDefault())?.toInstant()?.toEpochMilli()
    }
}

which, as other good answers already said, it's declared on the Database abstract class:

@Database(entities = {User.class}, version = 1)
@TypeConverters({Converters.class})
public abstract class AppDatabase extends RoomDatabase {
    public abstract UserDao userDao();
}

Room Using Date field

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