如何在 Android 中获取 Firestore POSTID 集合的大小？ [复制]

Question

查看代码：

private void initFirebase() {
        try {
            for (int i = 1; i < 16; i++) {
                mDatabase.collection(POST_ID).document("1").collection(PREVIEW)
                        .get()
                        .addOnCompleteListener(new OnCompleteListener<QuerySnapshot>() {
                            @Override
                            public void onComplete(@NonNull Task<QuerySnapshot> task) {
                                if (task.isSuccessful()) {
                                    for (QueryDocumentSnapshot document : task.getResult()) {
                                        postMap.putAll(document.getData());
                                    }
                                    if (postMap != null) {
                                        Post post = new Post();
                                        post.setTitle(Objects.requireNonNull(postMap.get(POST_NAME)).toString());
                                        post.setDesc(Objects.requireNonNull(postMap.get(POST_DESC)).toString());
                                        post.setUrl(Objects.requireNonNull(postMap.get(POST_URL)).toString());
                                        postList.add(post);
                                    }

                                    setAdapter();
                                } else {
                                    showLog("Error getting documents: " + task.getException());
                                }
                            }
                        });
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

而不是 for (int i = 1; i < 16; i++) { 16 我想要我的 Firestore 集合中存在的大小。我尝试了所有建议，但没有mDatabase.collection(POST_ID).size()

数据库结构：

Firestore-root
     |
     --- PostId (collecton)
          |
          --- 

我想要 postId 集合的大小。

Answer 1

尺寸

int count = 0;
db.collection("POST_ID")
    .get()
    .addOnCompleteListener(new OnCompleteListener<QuerySnapshot>() {
        @Override
        public void onComplete(@NonNull Task<QuerySnapshot> task) {
            if (task.isSuccessful()) {
               count = task.getResult().size();
            } else {
                Log.d(TAG, "Error getting documents: ", task.getException());
            }
        }
    });

private void initFirebase() {
        try {
            for (int i = 0; i < count; i++) {
                mDatabase.collection(POST_ID).document(i).collection(PREVIEW)
                        .get()
                        .addOnCompleteListener(new OnCompleteListener<QuerySnapshot>() {
                            @Override
                            public void onComplete(@NonNull Task<QuerySnapshot> task) {
                                if (task.isSuccessful()) {
                                    for (QueryDocumentSnapshot document : task.getResult()) {
                                        postMap.putAll(document.getData());
                                    }
                                    if (postMap != null) {
                                        Post post = new Post();
                                        post.setTitle(Objects.requireNonNull(postMap.get(POST_NAME)).toString());
                                        post.setDesc(Objects.requireNonNull(postMap.get(POST_DESC)).toString());
                                        post.setUrl(Objects.requireNonNull(postMap.get(POST_URL)).toString());
                                        postList.add(post);
                                    }

                                    setAdapter();
                                } else {
                                    showLog("Error getting documents: " + task.getException());
                                }
                            }
                        });
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

然后使用这个count 变量作为大小。