将新值添加到Firebase实时数据库时如何保存当前日期/时间

问题描述

当我通过控制面板向Firebase实时数据库添加新值时，我想在特定字段中保存当前日期/时间。

I want to save the current date/time in specific field when I add new value to Firebase Realtime Database via control panel.

我该如何实现？

请帮帮我。

推荐答案

最佳做法是保存你的数据为 TIMESTAMP ，如此 ServerValue.TIMESTAMP 。

The best practice is to save your data as a TIMESTAMP like this ServerValue.TIMESTAMP.

DatabaseReference ref = FirebaseDatabase.getInstance().getReference();
Map map = new HashMap();
map.put("timestamp", ServerValue.TIMESTAMP);
ref.child("yourNode").updateChildren(map);

还要记住，当你设置 TIMESTAMP ，你将它设置为 Map ，但是当你检索它时，你将它检索为 Long 。为了获得数据，我建议你使用这个方法：

Also remember, when you set the TIMESTAMP, you set it as a Map, but when you retrieve it, you retrieve it as a Long. To get the data back, i suggest you use this method:

public static String getTimeDate(long timestamp){
    try{
        DateFormat dateFormat = getDateTimeInstance();
        Date netDate = (new Date(timestamp));
        return dateFormat.format(netDate);
    } catch(Exception e) {
        return "date";
    }
}

编辑：模型class应如下所示：

The model class should look like this:

public class YourModelClass {
    //private fields
    private Map<String, String> timestamp;

    public YourModelClass() {}

    //public setters and getters for the fields

    public void setTimestamp(Map<String, String> timeStamp) {this.timestamp= timestamp;}
    public Map<String, String> getTimestamp() {return timestamp;}
}

记住， ServerValue.TIMESTAMP 只是Firebase实时数据库在写入操作期间用作子值时Firener实时数据库转换为服务器端号码的标记。写入操作完成后，日期仅出现在数据库中。

Remember, ServerValue.TIMESTAMP is just a token that Firebase Realtime Database converts to a number on server side when it's used as a child value during write operation. The date only appears in the database after the write operation completes.

要获得时间戳，还有另一个方法，即在中编写一个函数，它将是简单如下：

To get the timestamp, there is also another approach, which would be to write a frunction in Cloud Functions for Firebase and it will be as easy as:

exports.currentTime = functions.https.onRequest((req, res) => {
    res.send({"timestamp":new Date().getTime()})
})

您可以在云功能中托管此功能，并在无需用户交互的情况下获取服务器时间戳。

You can host this in Cloud Function and get the server timestamp without user interaction.

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