无法在 recyclerview android 中显示聊天消息的分组日期视图

Question

如何在我的应用中进行分组并显示日期视图。我正在使用 recyclerview 和 java 来显示此消息

结构：

   --------- **12-04-2021** ----------

--Leftsidemessage--
          ----rightsidemessgae----
--Leftsidemessage--
          ----rightsidemessgae----
--Leftsidemessage--
          ----rightsidemessgae----

    --------- **13-04-2021** ----------
--Leftsidemessage--
          ----rightsidemessgae----
--Leftsidemessage--
          ----rightsidemessgae----
--Leftsidemessage--
          ----rightsidemessgae----

以上是消息结构。我可以通过下面的代码显示右侧和左侧的消息，但它无法在我的应用中显示日期时间视图。

在此如何对特定日期消息下的消息进行分组和显示。

我的聊天适配器代码在这里。

 @Override
        public int getItemViewType(int position) {
            Message message = (Message) msgDtoList.get(position);
            if (minemsg) {
                // If the current user is the sender of the message
                return VIEW_TYPE_MESSAGE_SENT;
            }
            if (!minemsg) {
                // If some other user sent the message
                return VIEW_TYPE_MESSAGE_RECEIVED;
            }
    
            if (message.getmSentTime() != "") { // here the message senttime is always print inside this condition. But failed to show the view in the app.
                return DATE_VIEW_TYPE;
            }
    
            return 0;
        }
     @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.sender_message_layout, parent, false);
                return new SenderMessageHolder(view);
    
            }
            if (viewType == VIEW_TYPE_MESSAGE_RECEIVED) {
                view = LayoutInflater.from(parent.getContext())
                        .inflate(R.layout.receiver_message_layout, parent, false);
                return new ReceiverMessageHolder(view);
            }
    
            if (viewType == DATE_VIEW_TYPE) {
                view = LayoutInflater.from(parent.getContext())
                        .inflate(R.layout.date_view, parent, false);
                return new DateViewHolder(view);
            }
    
            return null;
        }

 @Override
    public void onBindViewHolder(RecyclerView.ViewHolder holder, int position) {
        Message message = (Message) msgDtoList.get(position);

        switch (holder.getItemViewType()) {
            case VIEW_TYPE_MESSAGE_SENT:
                populateSentViewHolder(holder, position);
                break;
            case VIEW_TYPE_MESSAGE_RECEIVED:
                populateReceivedViewHolder(holder, position);
                break;

            case DATE_VIEW_TYPE:
                populateDateViewHolder(holder, position);
                break;
        }
    }

我的聊天片段：

  @Override
    public void onViewCreated(View v, @Nullable Bundle b) {
        super.onViewCreated(v, b);
        LinearLayoutManager linearLayoutManager = new LinearLayoutManager(getActivity());
        linearLayoutManager.setOrientation(LinearLayoutManager.VERTICAL);
        linearLayoutManager.setStackFromEnd(true);
        linearLayoutManager.setSmoothScrollbarEnabled(true);
        linearLayoutManager.setReverseLayout(false);
        mRecyclerView.setLayoutManager(linearLayoutManager);

        int newMsgPosition = mAdapter.getItemCount();
        mRecyclerView.setHasFixedSize(true);
        mRecyclerView.setAdapter(mAdapter);
}

Answer 1

由于minemsg 为真或假，返回DATE_VIEW_TYPE 的代码将永远无法到达。即，遵循以下伪代码：

boolean minemsg = true;
if (minemsg)
{
  return;
}
if (!minemsg)
{
  return;
}
// anything after this would never be reached!, as minemsg is either true or false.

从您的问题看不清楚minemsg是什么，请尝试更改评估顺序如下：

    @Override
    public int getItemViewType(int position) {
        Message message = (Message) msgDtoList.get(position);
        
        // check for date record first
        if (message.getmSentTime() != "") { // here the message senttime is always print inside this condition. But failed to show the view in the app.
            return DATE_VIEW_TYPE;
        }

        if (minemsg) {
            // If the current user is the sender of the message
            return VIEW_TYPE_MESSAGE_SENT;
        }
        if (!minemsg) {
            // If some other user sent the message
            return VIEW_TYPE_MESSAGE_RECEIVED;
        }

        
        return 0;
    }

编辑：阅读下面的 cmets 后，您的问题要深得多，您正试图显示带有部分/组标题的单个 ArrayList 消息。

这超出了您提出的问题的范围，并且似乎已经有了答案，例如：

How to implement RecyclerView with section header depending on category?

Answer 2

试试这个：

 @Override
        public int getItemViewType(int position) {
            Message message = (Message) msgDtoList.get(position);
    
            // Since message can either be "mine" or "not mine" lets check the sent time first, and return the DATE_VIEW_TYPE to avoid dead code
            if (message.getmSentTime() != "") { // here the message senttime is always print inside this condition. But failed to show the view in the app.
                return DATE_VIEW_TYPE;
            }

            if (minemsg) {
                // If the current user is the sender of the message
                return VIEW_TYPE_MESSAGE_SENT;
            }
            if (!minemsg) {
                // If some other user sent the message
                return VIEW_TYPE_MESSAGE_RECEIVED;
            }
            // Everything below is "dead, unreachable code" due to booleans being either true or false
    
            return 0;
        }