Like and unlike system with Firebase not working

Question

I am trying to make simple like and unlike system but when I press the like button it just goes up I can not unlike,the counter doesn't go down for example if I have 5 likes and I unlike the value stays at 5. I am new to Firebase Android programming and I don't know how to implement this properly I hope someone can help me.

Here is my code, I can post the whole thing if this is not the correct one.

private void setUpVote(final ViewHolder holder) {
        final DatabaseReference reference = FirebaseDatabase.getInstance().getReference();
        final String userId = holder.post.getUser_id();
        final String postId = holder.post.getPost_id();
        holder.mUpVote.setOnLikeListener(new OnLikeListener() {
            @Override
            public void liked(LikeButton likeButton) {
                reference.child("up_votes").child(holder.currentUserID).child(holder.post.getPost_id()).setValue("true");
                reference.child("posts").child(holder.post.getPost_id()).child("up_votes").child(holder.currentUserID).setValue("true");
                getUpVote(holder);
                holder.mDownVote.setEnabled(false);
                setUserPoints(userId, holder);
                setPostPoints(postId, holder);
            }

            @Override
            public void unLiked(LikeButton likeButton) {

            }
        });
    }

    private void getUpVote(final ViewHolder holder) {
        String postID = holder.post.getPost_id();
        final DatabaseReference reference = FirebaseDatabase.getInstance().getReference();
        DatabaseReference newReference = reference.child("posts").child(postID).child("up_votes");
        newReference.addValueEventListener(new ValueEventListener() {
            @Override
            public void onDataChange(DataSnapshot dataSnapshot) {
                // This method is called once with the initial value and again
                // whenever data at this location is updated.
                if (dataSnapshot.hasChild(holder.currentUserID)) {
                    holder.upVotedByCurrentUser = true;
                    setState(holder);
                } else {
                    holder.upVotedByCurrentUser = false;
                }
                long numUpVotes = dataSnapshot.getChildrenCount();

                holder.mCountUpVote.setText(String.valueOf(numUpVotes));
            }


            @Override
            public void onCancelled(DatabaseError error) {
                // Failed to read value
                Log.w(TAG, "Failed to read value.", error.toException());
            }
        });
    }

    private void setDownVote(final ViewHolder holder) {
        final DatabaseReference reference = FirebaseDatabase.getInstance().getReference();
        final String postId = holder.post.getPost_id();
        holder.mDownVote.setOnLikeListener(new OnLikeListener() {
            @Override
            public void liked(LikeButton likeButton) {
                reference.child("down_votes").child(holder.currentUserID).child(holder.post.getPost_id()).setValue("true");
                reference.child("posts").child(holder.post.getPost_id()).child("down_votes").child(holder.currentUserID).setValue("true");
                getDownVote(holder);
                holder.mUpVote.setEnabled(false);
                setPostPoints(postId, holder);
            }

            @Override
            public void unLiked(LikeButton likeButton) {
            }
        });
    }

    private void getDownVote(final ViewHolder holder) {
        String postID = holder.post.getPost_id();
        final DatabaseReference reference = FirebaseDatabase.getInstance().getReference();
        DatabaseReference newReference = reference.child("posts").child(postID).child("down_votes");
        newReference.addValueEventListener(new ValueEventListener() {
            @Override
            public void onDataChange(DataSnapshot dataSnapshot) {
                // This method is called once with the initial value and again
                // whenever data at this location is updated.
                if (dataSnapshot.hasChild(holder.currentUserID)) {
                    holder.downVotedByCurrentUser = true;
                    setState(holder);
                } else {
                    holder.downVotedByCurrentUser = false;
                }
                long numDownVotes = dataSnapshot.getChildrenCount();

                holder.mCountDownVote.setText(String.valueOf(numDownVotes));
            }

I hope someone can help me!

Answer 1

This is not the best way in which you can manage this kind of problems. When it comes to likes and unlikes, the first problem that comes up is related to concurrent modifications in which case you should use transactions in order to have accurate data in your database.

So in this case, I recommend you to use my answer from post but instead of score you should use likes. The same principle applies.