如何从Firestore Android中的集合中获取文档列表 [英] How to get list of documents from a collection in Firestore Android

问题描述

我的Firestore数据库结构:

My structure of Firestore database:

|
|=>root_collection
                  |
                  |=>doc1
                         |                  
                         |=>collection
                  |
                  |=>doc2
                         |                  
                         |=>collection
                  |
                  |=>doc3
                         |                  
                         |=>collection

现在我想从root_collection获取文档列表.将存在一个包含以下数据{"doc1", "doc2", "doc3"}的列表.我需要它是因为我想制作一个微调器并将这些数据放入微调器中.然后，用户将选择一些文档并下载.

Now I wanna get list of document from root_collection. There would be a list with following data {"doc1", "doc2", "doc3"}. I need it because I want to make a spinner and put these data in the spinner. Then a user would be choose some document and download it.

我尝试使用下面的代码:

I try to use the code below:

firestore.collection("root_collection")
            .get()
            .addOnCompleteListener(new OnCompleteListener<QuerySnapshot>() {
                @Override
                public void onComplete(@NonNull Task<QuerySnapshot> task) {
                    if (task.isSuccessful()) {
                        for (QueryDocumentSnapshot document : task.getResult()) {
                            Log.d(TAG,document.getId() + " => " + document.getData());
                        }
                    } else {
                        Log.d(TAG, "Error getting documents: ", task.getException());
                    }
                }
            });

但是代码只有在我具有没有文档集合的数据结构的情况下才起作用.在其他情况下，QueryDocumentSnapshot中没有任何文档.

But the code works only then I have structure of data without collections in the documents. In other case there aren't any documents in QueryDocumentSnapshot.

谢谢！

推荐答案

要获取包含root_collection中所有文档名称的列表，请使用以下代码:

To have a list that contains all the name of your documents within the root_collection, please use the following code:

firestore.collection("root_collection").get().addOnCompleteListener(new OnCompleteListener<QuerySnapshot>() {
    @Override
    public void onComplete(@NonNull Task<QuerySnapshot> task) {
        if (task.isSuccessful()) {
            List<String> list = new ArrayList<>();
            for (QueryDocumentSnapshot document : task.getResult()) {
                list.add(document.getId());
            }
            Log.d(TAG, list.toString());
        } else {
            Log.d(TAG, "Error getting documents: ", task.getException());
        }
    }
});

您的logcat中的结果将是:

The result in your logcat will be:

[doc1, doc2, doc3]

请记住，仅当这些文档中具有某些属性时，此代码才有效，否则，您将以空列表结尾

Remember, this code will work, only if you'll have some properties within those documents, otherwise you'll end ut with an empty list.

这篇关于如何从Firestore Android中的集合中获取文档列表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！