如何根据创建时间对 Firebase 数据进行排序? [英] How to sort Firebase data according to Time Created?

问题描述

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大家好，我已经使用 Query 从应用中的 Firebase 实时数据库加载了一些数据.

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这是简单的代码:

 Query query = databaseReference.orderByChild("name").startAt(data).endAt(data + "\uf8ff");options = new FirebaseRecyclerOptions.Builder().setQuery(query, HomeModel.class).build();

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我的数据库结构很简单;

M38dJdquf4jE(随机密钥)名称:约翰·多伊"图片:图片链接"

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由于orderByChild(name")，每当有新数据插入数据库时​​，都不是根据插入数据的时间.相反，它以随机顺序将数据插入到 recyclerView 中.

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我该如何修复它，以便最后插入的数据始终位于 recyclerView 中的最后，而不是以随机方式插入.

解决方案

因为orderByChild("name")，每当有新数据插入数据库时​​，都不是按照时间

当您使用时:

.orderByChild("name")

这意味着来自数据库的结果将根据name"中存在的值进行排序.属性，并且不是根据时间".

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相反，它以随机顺序将数据插入到 RecyclerView 中.

如上所述，这绝对不是随机顺序.如果需要根据时间"获取结果的加法，那么你有两个选择.

例如，如果M38dJdquf4jE"是由push()"提供的按键.方法，您可以使用 Query 的 orderBykey() 方法，其中:

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创建一个查询，其中子节点按其键进行排序.

您将得到有序的结果，因为按下的键包含时间组件.

如果这些键不由push()"提供，方法，要根据时间组件进行排序，那么您应该添加一个时间戳"类型的属性，如我在以下帖子中的回答中所述:

• 向 Firebase 实时数据库添加新值时如何保存当前日期/时间

一旦你有了新的属性，你就可以使用:

.orderByChild(时间戳")

让结果按升序排列.但是，如果您需要降序，则可以使用我在以下帖子中的回答:

• 如何安排firebase数据库数据升序还是降序?

Hello Everyone, I have loaded some data from Firebase Realtime Database in the App using Query.

This is the Simple code :

  Query query = databaseReference.orderByChild("name").startAt(data).endAt(data + "\uf8ff");

  options = new FirebaseRecyclerOptions.Builder<HomeModel>().setQuery(query, HomeModel.class).build();

My database structure is simple ;

M38dJdquf4jE(the random key)
name : "John Doe"
Image : "image link"

Because of orderByChild("name"), whenever a new Data is inserted in the Database is not according to the Time the data is inserted. Instead, it inserts the data in the recyclerView in a Random Order.

How can I fix it, so that the Last data inserted is always at the last in the recyclerView and not inserted in a random manner.

解决方案

Because of orderByChild("name"), whenever a new Data is inserted in the Database is not according to the Time

When you are using:

.orderByChild("name")

It means that the results that are coming from the database will be ordered according to the values that exist in the "name" property, and not according to a "time".

Instead, it inserts the data in the RecyclerView in a Random Order.

As said above, that's definitely not a random order. If you need to get the results according to the "time" of the addition, then you have two options.

If, for example, the "M38dJdquf4jE" is a pushed key that is provided by the "push()" method, you can use Query's orderBykey() method, which:

Creates a query in which child nodes are ordered by their keys.

You'll get the results ordered because the pushed keys contain a time component.

If those keys are not provided by the "push()" method, to have an order according to a time component, then you should add a property of type "timestamp", as explained in my answer from the following post:

• How to save the current date/time when I add new value to Firebase Realtime Database

Once you have that new property in place, you can use:

.orderByChild("timestamp")

To have the results ordered ascending. If you need however a descending order, then you can use my answer from the following post:

• How to arrange firebase database data in ascending or descending order?

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