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java - How to read same value from nodes with different keys in Firebase real-time database?

问题描述

So I'm trying to display a list of comments under a post in a RecyclerView. However, I always run into the problem that I can't read the correct value because I don't know how to output the right path when the keys differ.

Can somebody help me?

Here's my structure in Firebase:

enter image description here

Here's my code so far: 

 private void loadComments() {
        DatabaseReference commentRef = mRootReference.child("comments").child(pollid).getParent().child("comment");
        Query commentQuery = commentRef.limitToLast(mCurrentPage * TOTAL_ITEMS_TO_LOAD);
        commentQuery.addChildEventListener(new ChildEventListener() {
            @Override
            public void onChildAdded(DataSnapshot dataSnapshot, String s) {
                for (DataSnapshot ds : dataSnapshot.getChildren()) {
                    Comment comment = ds.getValue(Comment.class);
                    commentList.add(comment);
                    mAdapter.notifyDataSetChanged();
                    mCommentList.scrollToPosition(commentList.size() - 1);
                }
            }

            @Override
            public void onChildChanged(DataSnapshot dataSnapshot, String s) {

            }

            @Override
            public void onChildRemoved(DataSnapshot dataSnapshot) {

            }

            @Override
            public void onChildMoved(DataSnapshot dataSnapshot, String s) {

            }

            @Override
            public void onCancelled(DatabaseError databaseError) {

            }
        });
    }

标签： javaandroidfirebasefirebase-realtime-database

解决方案

看到您的数据库架构和代码，我假设pollid您的引用中指定的变量包含LKwV ... IRyZ. 因此，要显示该节点内的所有评论，请使用以下代码行：

DatabaseReference rootRef = FirebaseDatabase.getInstance().getReference();
Query query = rootRef.child("comments").child(pollid).orderByChild("time");
ValueEventListener valueEventListener = new ValueEventListener() {
    @Override
    public void onDataChange(DataSnapshot dataSnapshot) {
        List<Comment> list = new ArrayList<>();
        for(DataSnapshot ds : dataSnapshot.getChildren()) {
            Comment comment = ds.getValue(Comment.class);
            commentList.add(comment);
        }

        //Do what you need to do with your list
        //Pass the list to the adapter and set the adapter
    }

    @Override
    public void onCancelled(@NonNull DatabaseError databaseError) {
        Log.d(TAG, databaseError.getMessage());
    }
};
query.addListenerForSingleValueEvent(valueEventListener);

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