java - 解包数据 firestore 查询返回的数组类型

Question

这会返回一个 ArrayList，其中包含我存储在 Firestore 中的图像 Uris。我如何解包数组列表并一个一个地提取它们？下面是 logcat 的示例输出。

{0= https://firebasestorage.googleapis.com/v0/b/app ........., 1= https://firebasestorage.googleapis.com/v0/b/app ........., 2= https://firebasestorage.googleapis.com/v0/b/app

    firebaseFirestore.collection("Ads").whereEqualTo("user_id",user_id).get().addOnCompleteListener(new OnCompleteListener<QuerySnapshot>() {
        @Override
        public void onComplete(@NonNull Task<QuerySnapshot> task) {
            if (task.isSuccessful()) {
                if (task.isSuccessful()) {
                    for (QueryDocumentSnapshot document : task.getResult()) {
                        Map<String, Object> map = document.getData();
                        for (Map.Entry<String, Object> entry : map.entrySet()) {
                            ArrayList<String> imgUri = (ArrayList<String>) entry.getValue();
                            for (String uri : imgUri) {
                                Log.d(TAG, uri);
                            }
                        }
                    }
                }
            }

db structure

Answer 1

要解决这个问题，请使用以下代码行:

FirebaseFirestore rootRef = FirebaseFirestore.getInstance();
rootRef.collection("Ads").whereEqualTo("user_id", user_id).get().addOnCompleteListener(new OnCompleteListener<QuerySnapshot>() {
    @Override
    public void onComplete(@NonNull Task<QuerySnapshot> task) {
        if (task.isSuccessful()) {
            for (QueryDocumentSnapshot document : task.getResult()) {
                Map<String, Object> map = (Map<String, Object>) document.get("imgUri");
                for (Map.Entry<String, Object> entry : map.entrySet()) {
                    Log.d(TAG, entry.getValue().toString());
                }
            }
        }
    }
});

输出将是:

https://firebasestorage.googleapis.com/v0/b/app.........,
https://firebasestorage.googleapis.com/v0/b/app........., 
https://firebasestorage.googleapis.com/v0/b/app.........,