根据ID或属性迭代Firestore Android集合 [英] Iterating Firestore Android collection on basis of ID or attribute

问题描述

我想迭代一个从集合文档ID开始的集合。

I want to iterate a collection which starts at collection document ID.

是否有类似下面的方法让我们以id或属性ID读取数据？

Is there any method like below which let us read data start at an id or an attribute id?

 db.collection("questions").startReadingDocumentAt("02cubnmO1wqyz6yKg571 ").limit(10).get() 

或

db.collection("questions").startReadingWhereEqualTo("questionID","02cubnmO1wqyz6yKg571 ").limit(10).get()

我知道我可以根据Id 读取DocumentSnapShot，然后可以开始使用lastVisible项进行迭代。但它花了我两个读操作。它可以在一个完成。

I know I can read that DocumentSnapShot on basis of Id and can then start iterating with lastVisible item. but it cost me two read operation. Can it be done in one.

Firestore-root
    |
    --- questions (collections)
    |     |
    |     --- 02cubnmO1wqyz6yKg571 (questionId document) // myID and my questionID is same
    |            |
    |            --- questionId: "02cubnmO1wqyz6yKg571"
    |            |
    |            --- title: "Question Title"
    |            |
    |            --- date: August 27, 2018 at 6:16:58 PM UTC+3
    |            |

我已经离开 通过此

I already have gone through this

解释

我不想做 RecyclerView分页。我想在每次活动开始时加载下一个10个问题。所以我以相同的方式调用查询，但它需要我保存 DocumentSnapShot 。所以我决定保存questionID并根据它读取数据...

I don't want to do RecyclerView pagination. I want to load next 10 question each time an Activity starts. So I call the query in the same manner but it requires me to save the DocumentSnapShot. So I decided to save the questionID and read data on basis of it...

推荐答案

没有：

startReadingDocumentAt("02cubnmO1wqyz6yKg571")

也

startReadingWhereEqualTo("questionID","02cubnmO1wqyz6yKg571")

在firestore中，但根据您的数据库架构，要解决此问题，您可以使用以下查询：

In firestore but according to your database schema, to solve this, you can use the following query:

db.collection("questions").
    whereGreaterThanOrEqualTo("questionID","02cubnmO1wqyz6yKg571")
    .limit(10)
    .get()
    addOnCompleteListener.(/* ... */)

更多信息这里：

创建并返回一个新的Query，其中包含文档必须包含指定字段的附加过滤器，且值应大于或等于指定值。

Creates and returns a new Query with the additional filter that documents must contain the specified field and the value should be greater than or equal to the specified value.

这篇关于根据ID或属性迭代Firestore Android集合的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！