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我正在尝试将我的 LocalDateTime 字段保存为 long，以便我可以将其存储在我的 SQLite 数据库中。我怎么能做到这一点？

var datetime = LocalDateTime.now()
var longdt: Long = getString(datetime).toLong()
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2 回答 2

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您可以使用toEpochSecond()and将一个精确到秒的值ofEpochSecond()转换为/从一个值转换。long

示例（在 Java 中）

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，您应该使用ZonedDateTimeorOffsetDateTime代替LocalDateTime。

于 2020-05-12T16:13:01.060 回答
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如果用 long 表示以这种方式使用的秒数或毫秒数。

LocalDateTime 以 Epoch 秒为单位

val seconds = datetime.atZone(ZoneOffset.UTC).toEpochSecond())

LocalDateTime 到纪元毫秒

val milliseconds = datetime.atZone(ZoneOffset.UTC)?.toInstant()?.toEpochMilli()
于 2020-05-12T15:55:54.827 回答