如何使用 Firebase Firestore 获取查询数据？

Question

Query query = mTournamentColRef.whereEqualTo("author", user.getUid());

I want to get the id of the Document inside mTournamentColRef , but could not find anything in the Firebase documentation talking about what to do with the query and how to get its data.

Thank you for your help!

Answer 1

You can use data snapshot to get data from query or if you are using Firestore Recycler Adapter you can directly pass the query to the constructor. Here is the code to get specific data:-

Query query = mTournamentColRef.whereEqualTo("author", user.getUid());
            query.addSnapshotListener(new EventListener<QuerySnapshot>() {
                @Override
                public void onEvent(QuerySnapshot queryDocumentSnapshots, FirebaseFirestoreException e)
                {
                    for (DocumentSnapshot doc : queryDocumentSnapshots)
                    {
                        Tournament tp = doc.toObject(Tournament.class);
                    }
                }
            });

Answer 2

How to get query data using firebase firestore?

Simply, use a get() call!

query.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 Id: " + document.getId());
            }
        }
    }
});

There is no need to use addSnapshotListener unless you need to get the data in real-time. If you only need to get it and not listen for changes, just use the get() method.

Answer 3

你可以通过 dicumentsnapshot.getId() 获得我想要的文件