聊天RecyclerView为空白，什么也没显示，但正在获取数据

Question

我正在尝试以聊天形式显示Recyclerview，但是为空，这里找不到代码的问题，我不知道问题在哪里，但是可能在适配器中。

MessageListAdapter.java

public class MessageListAdapter extends RecyclerView.Adapter {
private static final int VIEW_TYPE_MESSAGE_SENT = 1;
private static final int VIEW_TYPE_MESSAGE_RECEIVED = 2;

private Context mContext;
private List<ItemMessage> mMessageList;

public MessageListAdapter(Context context, List<ItemMessage> messageList) {
    mContext = context;
    mMessageList = messageList;
}

@Override
public int getItemCount() {
    return mMessageList.size();
}

// Determines the appropriate ViewType according to the sender of the message.
@Override
public int getItemViewType(int position) {
    ItemMessage message = mMessageList.get(position);

    if (message.getSender().equals(FirebaseAuth.getInstance().getCurrentUser().getUid())) {
        // If the current user is the sender of the message
        return VIEW_TYPE_MESSAGE_SENT;
    } else {
        // If some other user sent the message
        return VIEW_TYPE_MESSAGE_RECEIVED;
    }
}

// Inflates the appropriate layout according to the ViewType.
@Override
public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
    View view;

    if (viewType == VIEW_TYPE_MESSAGE_SENT) {
        view = LayoutInflater.from(parent.getContext())
                .inflate(R.layout.item_message_sent, parent, false);
        return new SentMessageHolder(view);
    } else if (viewType == VIEW_TYPE_MESSAGE_RECEIVED) {
        view = LayoutInflater.from(parent.getContext())
                .inflate(R.layout.item_message_received, parent, false);
        return new ReceivedMessageHolder(view);
    }

    return null;
}

// Passes the message object to a ViewHolder so that the contents can be bound to UI.
@Override
public void onBindViewHolder(RecyclerView.ViewHolder holder, int position) {
    ItemMessage message =  mMessageList.get(position);

    switch (holder.getItemViewType()) {
        case VIEW_TYPE_MESSAGE_SENT:
            ((SentMessageHolder) holder).bind(message);
            break;
        case VIEW_TYPE_MESSAGE_RECEIVED:
            ((ReceivedMessageHolder) holder).bind(message);
    }
}

private class SentMessageHolder extends RecyclerView.ViewHolder {
    TextView messageText, timeText;

    SentMessageHolder(View itemView) {
        super(itemView);

        messageText = (TextView) itemView.findViewById(R.id.text_message_body);
        timeText = (TextView) itemView.findViewById(R.id.text_message_time);
    }

    void bind(ItemMessage message) {
        messageText.setText(message.getMessgae());

        // Format the stored timestamp into a readable String using method.
        timeText.setText(message.getTime());
    }
}

private class ReceivedMessageHolder extends RecyclerView.ViewHolder {
    TextView messageText, timeText, nameText;
    ImageView profileImage;

    ReceivedMessageHolder(View itemView) {
        super(itemView);

        messageText = (TextView) itemView.findViewById(R.id.text_message_body);
        timeText = (TextView) itemView.findViewById(R.id.text_message_time);
        nameText = (TextView) itemView.findViewById(R.id.text_message_name);
        profileImage = (ImageView) itemView.findViewById(R.id.image_message_profile);
    }

    void bind(ItemMessage message) {
        messageText.setText(message.getMessgae());

        // Format the stored timestamp into a readable String using method.
        timeText.setText(message.getTime());

        nameText.setText("kdkdk");

        // Insert the profile image from the URL into the ImageView.
       // Utils.displayRoundImageFromUrl(mContext, message.getSender().getProfileUrl(), profileImage);
    }
}
}

ItemMessage.java

public class ItemMessage {
private String sender = null;
private String reciever = null;
private String time = null;
private String messgae =  null;

public ItemMessage() {

}

public ItemMessage(String sender, String reciever, String time, String messgae) {
    this.sender = sender;
    this.reciever = reciever;
    this.time = time;
    this.messgae = messgae;
}

public String getSender() {
    return sender;
}

public void setSender(String sender) {
    this.sender = sender;
}

public String getReciever() {
    return reciever;
}

public void setReciever(String reciever) {
    this.reciever = reciever;
}

public String getTime() {
    return time;
}

public void setTime(String time) {
    this.time = time;
}

public String getMessgae() {
    return messgae;
}

public void setMessgae(String messgae) {
    this.messgae = messgae;
}
}

获取代码。

childEventListener = new ChildEventListener() {
        @Override
        public void onChildAdded(DataSnapshot dataSnapshot, String s) {

            ItemMessage itemMessage = dataSnapshot.getValue(ItemMessage.class);
            friendlyMessages.add(itemMessage);
            mMessageAdapter.notifyDataSetChanged();
            Log.d("SSSSz" , friendlyMessages.size()+"");
            Log.d("SSSSz", itemMessage.getMessgae());
        }

        @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) {

        }
    };

    databaseReferencemsg.addChildEventListener(childEventListener);

我没有发布其余的代码，因为我知道问题在这里。