如何从 Cloud Firestore 的数组数据字段中获取数据？

Question

我正在使用 Cloud Firestore，并且字段中有一个数组数据。那么如何单独从数组中获取数据呢？

Answer 1

要获取ip_range数组中的值，请使用以下代码行：FirebaseFirestore rootRef = FirebaseFirestore.getInstance();rootRef.collection("aic").document("ceo").get().addOnCompleteListener(new OnCompleteListener<DocumentSnapshot>() {&nbsp; &nbsp; @Override&nbsp; &nbsp; public void onComplete(@NonNull Task<DocumentSnapshot> task) {&nbsp; &nbsp; &nbsp; &nbsp; if (task.isSuccessful()) {&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; DocumentSnapshot document = task.getResult();&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; if (document.exists()) {&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; Map<String, Object> map = document.getData();&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; for (Map.Entry<String, Object> entry : map.entrySet()) {&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; if (entry.getKey().equals("ip_range")) {&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; Log.d("TAG", entry.getValue().toString());&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; }&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; }&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; }&nbsp; &nbsp; &nbsp; &nbsp; }&nbsp; &nbsp; }});另一种方法是：rootRef.collection("products").document("06cRbnkO1yqyzOyKP570").get().addOnCompleteListener(new OnCompleteListener<DocumentSnapshot>() {&nbsp; &nbsp; @Override&nbsp; &nbsp; public void onComplete(@NonNull Task<DocumentSnapshot> task) {&nbsp; &nbsp; &nbsp; &nbsp; if (task.isSuccessful()) {&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; DocumentSnapshot document = task.getResult();&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; if (document.exists()) {&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; ArrayList<String> list = (ArrayList<String>) document.get("ip_range");&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; Log.d(TAG, list.toString());&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; }&nbsp; &nbsp; &nbsp; &nbsp; }&nbsp; &nbsp; }});在这两种情况下，您的 logcat 中的输出将是：[172.16.11.1, 172.16.11.2]