Kotlin LocalDateTime as Long

Question

我正在尝试将 LocalDateTime 字段保存为 long，以便可以将其存储在 SQLite 数据库中。我怎样才能做到这一点？

var datetime = LocalDateTime.now()
var longdt: Long = getString(datetime).toLong()

Answer 1

您可以使用toEpochSecond()和与精确到秒的值ofEpochSecond()进行转换。long

示例（Java 语言）

LocalDateTime now = LocalDateTime.now();
long nowInSeconds = now.toEpochSecond(ZoneOffset.UTC);
LocalDateTime dateTime = LocalDateTime.ofEpochSecond(nowInSeconds, 0, ZoneOffset.UTC);

System.out.println("now = " + now);
System.out.println("nowInSeconds = " + nowInSeconds);
System.out.println("dateTime = " + dateTime);

输出

now = 2020-05-12T12:12:36.984263200
nowInSeconds = 1589285556
dateTime = 2020-05-12T12:12:36

如果您需要long精确到毫秒的值，请执行以下操作：

LocalDateTime now = LocalDateTime.now();
long nowInMillis = now.toEpochSecond(ZoneOffset.UTC) * 1000
                 + now.get(ChronoField.MILLI_OF_SECOND);
LocalDateTime dateTime = LocalDateTime.ofEpochSecond(nowInMillis / 1000,
                  (int) (nowInMillis % 1000 * 1000000), ZoneOffset.UTC);

System.out.println("now = " + now);
System.out.println("nowInMillis = " + nowInMillis);
System.out.println("dateTime = " + dateTime);

输出

now = 2020-05-12T12:16:38.881510700
nowInMillis = 1589285798881
dateTime = 2020-05-12T12:16:38.881

如果需要，请指定除 之外的区域偏移量UTC，但在这种情况下，您实际上应该使用ZonedDateTime或OffsetDateTime而不是LocalDateTime。