java - 检查文档是否存在于 Firestore 集合中

Question

我有一个 Firestore 集合树，我打算在其中只存储一个文档。我想检查该集合是否包含该文档，如果是，则检索文档的 ID!有什么想法吗？

谢谢:)

Answer 1

如果您想根据文档id检查特定文档是否存在，请使用以下代码行:

FirebaseFirestore rootRef = FirebaseFirestore.getInstance();
DocumentReference docIdRef = rootRef.collection("yourCollection").document(docId);
docIdRef.get().addOnCompleteListener(new OnCompleteListener<DocumentSnapshot>() {
    @Override
    public void onComplete(@NonNull Task<DocumentSnapshot> task) {
        if (task.isSuccessful()) {
            DocumentSnapshot document = task.getResult();
            if (document.exists()) {
                Log.d(TAG, "Document exists!");
            } else {
                Log.d(TAG, "Document does not exist!");
            }
        } else {
            Log.d(TAG, "Failed with: ", task.getException());
        }
    }
});

如果您没有文档 ID，则需要使用查询并根据特定属性的值查找该文档，如下所示:

FirebaseFirestore rootRef = FirebaseFirestore.getInstance();
CollectionReference yourCollRef = rootRef.collection("yourCollection");
Query query = yourCollRef.whereEqualTo("yourPropery", "yourValue");
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.getId() + " => " + document.getData());
            }
        } else {
            Log.d(TAG, "Error getting documents: ", task.getException());
        }
    }
});