java - 如何从 Firebase Firestore 获取数据？

Question

在此代码中，我在 firestore 中添加了“注释”，这不是问题。

btnAddComment.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                btnAddComment.setVisibility(View.INVISIBLE);
                DocumentReference comment = firestore.collection("Comment").document(postKey);
                String comment_content = editTextComment.getText().toString();
                String uid = currentUser.getUid();
                String uname = currentUser.getDisplayName();
                String uimg = currentUser.getPhotoUrl().toString();
                Comment comm = new Comment(comment_content, uid, uimg, uname);

                comment.set(comm).addOnSuccessListener(new OnSuccessListener<Void>() {
                    @Override
                    public void onSuccess(Void aVoid) {
                        showMessage("Добавлено");
                        editTextComment.setText("");
                        btnAddComment.setVisibility(View.VISIBLE);
                    }
                }).addOnFailureListener(new OnFailureListener() {
                    @Override
                    public void onFailure(@NonNull Exception e) {
                        showMessage("Не добавлено: " + e.getMessage());
                    }
                });
            }
        });

缝合方法如下:

private void iniRvComment() {
        RwComment.setLayoutManager(new LinearLayoutManager(this));
        DocumentReference docRef = firestore.collection("Comment").document(postKey);
        docRef.collection("Comment").addSnapshotListener(new EventListener<QuerySnapshot>() {
            @Override
            public void onEvent(@Nullable QuerySnapshot documentSnapshot, @Nullable FirebaseFirestoreException e) {
                if (documentSnapshot != null && !documentSnapshot.getDocuments().isEmpty()) {
                    listComment = new ArrayList<>();
                    List<DocumentSnapshot> documents = documentSnapshot.getDocuments();
                    for (DocumentSnapshot value : documents) {

                        Comment comment = value.toObject(Comment.class);
                        listComment.add(comment);
                    }
                    commentAdapter = new CommentAdapter(getApplicationContext(), listComment);
                    RwComment.setAdapter(commentAdapter);
                }
            }
        });
    }

我想使用“postKey”作为键使用 firestore 显示“评论”字段，但我可以理解这段代码的工作原理，在 Firebase 官方网站上观看了这一切。我在用户留下评论的每个帖子下都有一个“帖子”，问题是没有显示某些内容。

Answer 1

由于您的数据库引用声明，上述代码将不起作用。如果您想检索所有评论，只需提供集合引用即可。

firestore.collection("Comment").addSnapshotListener(new EventListener<QuerySnapshot>() {
    @Override
    public void onEvent(@Nullable QuerySnapshot documentSnapshot, @Nullable FirebaseFirestoreException e) {
        if (documentSnapshot != null && !documentSnapshot.getDocuments().isEmpty()) {
            listComment = new ArrayList<>();
            List<DocumentSnapshot> documents = documentSnapshot.getDocuments();
            for (DocumentSnapshot value : documents) {

                Comment comment = value.toObject(Comment.class);
                listComment.add(comment);
            }
            commentAdapter = new CommentAdapter(getApplicationContext(), listComment);
            RwComment.setAdapter(commentAdapter);
        }
    }
});