聊天应用使用Firebase

Question

我正在尝试使用firebase构建聊天应用程序我在firebase recyclerview适配器中遇到问题它显示此错误

无法将java.util.HashMap类型的值转换为String

我的结构用户 - ＆gt; IDuser - ＆gt;聊天 - ＆gt; id chat - ＆gt;消息 - ＆gt; id消息

聊天包含用户的所有deffrente对话

我的代码：

    @Override
protected void onStart() {
    super.onStart();
    Query query = FirebaseDatabase.getInstance().getReference().child("User").child(Cuid).child("Chat").child(idconvC).child("messages").getRef();
    FirebaseRecyclerOptions<Message> options =
            new FirebaseRecyclerOptions.Builder<Message>()
                    .setQuery(query,Message.class)
                    .build();
    firebaseRecyclerAdapter = new FirebaseRecyclerAdapter<Message,Conv.ConvViewHolder>
            (options) {
        @NonNull
        @Override
        public Conv.ConvViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
            // Create a new instance of the ViewHolder, in this case we are using a custom
            // layout called R.layout.message for each item
            View view = LayoutInflater.from(parent.getContext())
                    .inflate(R.layout.messagerow, parent, false);
            return new Conv.ConvViewHolder(view);
        }

        @Override
        protected void onBindViewHolder (@NonNull Conv.ConvViewHolder viewHolder,final int position,@NonNull Message model) {

            if (model.getUsername().equals(Cusername)) {
            viewHolder.seturi(getApplicationContext(),model.getUri());
            viewHolder.setusername(model.getUsername());
            viewHolder.setmsg(model.getMessage());
            viewHolder.itemView.setBackgroundColor(Color.parseColor("#d3d3d3"));
                // Gravity right

            }
            else {
                viewHolder.seturi(getApplicationContext(),model.getUri());
                viewHolder.setusername(model.getUsername());
                viewHolder.setmsg(model.getMessage());
                // Gravity left
                }

            }
    };

    recyclerView.setAdapter(firebaseRecyclerAdapter);
    firebaseRecyclerAdapter.startListening();
    }

我的数据库：