在Firebase中保存和检索日期

问题描述

我有一个具有以下结构的模型

I have a model with the following structure

public class OfferModel {
    private String mImageUrl;
    private String mOfferCode;
    private String mOfferTitle;
    private String mOfferDescription;
    private boolean mIsRunning;
    private String mCreatorUid;
    private Date mStartDate;
}

保存时其他一切正常。它在Firebase实时数据库中保存为

Everything else works fine on saving. It saves in Firebase Realtime database as

startDate
    date: 22
    day: 3
    hours: 23
    minutes: 20
    month: 5
    seconds: 50
    time: 1466617850476
    timezoneOffset: -330
    year: 116

但是当我尝试检索它时，日期会出现以下错误 -

But when I try to retrieve it, the date gives the following error -

java.lang.ClassCastException: java.util.HashMap cannot be cast to java.util.Date
at com.localvine.models.OfferModel.<init>(OfferModel.java:37)
at com.localvine.managers.OfferManager$1.onDataChange(OfferManager.java:62)
at com.google.android.gms.internal.zzafp.zza(Unknown Source)
at com.google.android.gms.internal.zzagp.zzSu(Unknown Source)
at com.google.android.gms.internal.zzags$1.run(Unknown Source)
at android.os.Handler.handleCallback(Handler.java:615)

我知道Firebase没有不支持Java Date对象，但是罪恶如果它将它们保存在地图中，我该如何从该地图中取回日期？在Firebase Android中是否有正确的保存和检索日期的方法？

I understand that Firebase doesn't support Java Date object, but since it's saving them in a map, how can I get back the date from that map? Is there any proper way of saving and retrieving dates in Firebase Android?

推荐答案

您可以将日期存储为纪元日期。您可以使用系统时间 System.currentTimeMillis（）; 或使用Firebase服务器时间及其 ServerValue.TIMESTAMP 。第一个选项是它随时区和系统设置而变化。因此，如果您将日期存储为长，则只需将 OfferModel 字段 mStartDate 更改为 long 然后使用 new Date（long）获取相应的日期检索对象时。

You can store the date as an epoch date. It's a long that you can get using your system time System.currentTimeMillis(); or by using the Firebase server time with their ServerValue.TIMESTAMP. The thing with the first option is that it changes with timezones and system settings. So if you store the date as a long, you just have to change your OfferModel field mStartDate to a long and then use new Date(long) to get the corresponding Date when retrieving the object.

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