Java Firebase Cloud Firestore：集合引用无效。集合引用必须具有奇数个段
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Firebase Cloud Firestore : Invalid collection reference. Collection references must have an odd number of segments
提问by Relm
I have the following code and getting an error :
我有以下代码并收到错误：
Invalid collection reference. Collection references must have an odd number of segments
And the code :
和代码：
private void setAdapter() {
FirebaseFirestore db = FirebaseFirestore.getInstance();
db.collection("app/users/" + uid + "/notifications").get().addOnCompleteListener(task -> {
if (task.isSuccessful()) {
for (DocumentSnapshot document : task.getResult()) {
Log.d("FragmentNotifications", document.getId() + " => " + document.getData());
}
} else {
Log.w("FragmentNotifications", "Error getting notifications.", task.getException());
}
});
}
采纳答案by Bob Snyder
Hierarchical data structures and subcollections are described in the documentation. A collection contains documents and a document may contain a subcollection. The structure is always an alternating pattern of collections and documents. The documentation contains this description of an example:
文档中描述了分层数据结构和子集合。一个集合包含文档，一个文档可能包含一个子集合。该结构始终是集合和文档的交替模式。该文档包含对示例的以下描述：
Notice the alternating pattern of collections and documents. Your collections and documents must always follow this pattern. You cannot reference a collection in a collection or a document in a document.
注意集合和文档的交替模式。您的集合和文档必须始终遵循此模式。您不能引用集合中的集合或文档中的文档。
Thus, a valid path to a collection will always have an odd number of segments; a valid path to a document, an even number. Since your code is trying to query a collection, the path length of four is invalid.
因此，集合的有效路径将始终具有奇数个段；文档的有效路径，偶数。由于您的代码正在尝试查询集合，因此路径长度为 4 是无效的。
回答by Diego Venancio
Then you need change this:
然后你需要改变这个：
db.collection("app/users/" + uid + "/notifications")...
for this:
为了这：
db.collection("app").document("users").collection(uid).document("notifications")
You welcome ;)
没关系 ;）
回答by Vikash Sharma
You are missing collection reference. i.e db.collection(** This is getting null **).
您缺少集合参考。即 db.collection(** 这是空的 **)。
回答by Radu Linu
I've encountered this issue when I provided a wrong entity_Id.
我在提供错误的 entity_Id 时遇到了这个问题。
Instead of dojo/default/datasets/fe67ec58-6208-4234-a4ee-98c5dce4665f,
I've provided fe67ec58-6208-4234-a4ee-98c5dce4665fand now is working fine.
而不是dojo/default/datasets/fe67ec58-6208-4234-a4ee-98c5dce4665f，我提供了fe67ec58-6208-4234-a4ee-98c5dce4665f，现在工作正常。
