Android Recyclerview在scrolltop上加载更多 [英] Android Recyclerview load more on scrolltop

问题描述

嘿社区，我想像聊天应用程序中那样创建一个 RecyclerView .

Hey community I want to make a RecyclerView like in the chat applications.

我尝试了 setStackFromEnd ，并且运行良好.

I tried setStackFromEnd and it's working good.

final LinearLayoutManager llm = new LinearLayoutManager(getApplicationContext());
    llm.setOrientation(LinearLayoutManager.VERTICAL);
    llm.setStackFromEnd(true);

根据本教程，我正在加载更多代码，在教程结束时，您应该看到一个视频: Recyclerview底部进度

My on load more code based on this tutorial, At the end of tutorial you should see a video : Recyclerview Bottom Progress

mRecyclerView.addOnScrollListener(new RecyclerView.OnScrollListener() {
        @Override
        public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
            super.onScrolled(recyclerView, dx, dy);

            totalItemCount = linearLayoutManager.getItemCount();
            lastVisibleItem = linearLayoutManager.findLastVisibleItemPosition();

            if (!isLoading && totalItemCount <= (lastVisibleItem + visibleThreshold)) {
                if (mOnLoadMoreListener != null) {
                    mOnLoadMoreListener.onLoadMore();
                }
                isLoading = true;
            }
        }
    });

所以我需要像聊天应用程序一样制作一个 RecyclerView .从头开始的堆栈工作完美，但是当我到达顶部而不是到达底部时，我需要触发更多的加载方法.还要在顶部而不是底部添加新项目.预先感谢.

So I need to make a RecyclerView like in chat applications. Stack from end is working perfect but I need to trigger load more method when I go top instead of going bottom. Also add new items on top instead of bottom. Thanks in advance.

推荐答案

如果您只想显示 Button ，则无需使用 onScrollListener 顶部的加载早期消息".您可以简单地创建一个 xml 来加载更多的 Button ，将其作为 RecyclerView 的第一行，并创建一个 Interface 处理点击事件.我正在从我的一个项目中发布 Adpater 的代码.希望这会帮助您获得一些进一步的想法.

You don't need to make use of onScrollListener, if you simply want to show a Button "Load Earlier Messages" at the top. You can simply create an xml for your load more Button, make that as the first row of your RecyclerView and create an Interface to handle click events. I am posting code for the Adpater from one of my projects. Hope that will help you in getting some idea to proceed further.

/**
 * Created by Mukesh on 21/12/2015.
 */
public class ChatListAdapter extends RecyclerView.Adapter<RecyclerView.ViewHolder> {

    private Context mContext;
    private List<UserMessage> userMessagesList;
    private LayoutInflater mLayoutInflater;
    private static final int ROW_TYPE_LOAD_EARLIER_MESSAGES = 0;
    private static final int ROW_TYPE_SENDER = 1;
    private static final int ROW_TYPE_RECEIVER = 2;
    private int userId;
    private boolean isLoadEarlierMsgs;
    private LoadEarlierMessages mLoadEarlierMessages;

    public ChatListAdapter(Context context, int userId, List<UserMessage> userMessagesList) {
        mContext = context;
        this.userMessagesList = userMessagesList;
        mLayoutInflater = LayoutInflater.from(mContext);
        this.userId = userId;
        mLoadEarlierMessages = (LoadEarlierMessages) mContext;
    }

    @Override
    public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        switch (viewType) {
            case ROW_TYPE_LOAD_EARLIER_MESSAGES:
                return new LoadEarlierMsgsViewHolder(mLayoutInflater.inflate(R.layout
                        .row_load_earlier_messages, parent, false));
            case ROW_TYPE_SENDER:
                return new SenderMsgViewHolder(mLayoutInflater.inflate(R.layout.row_sender_msg,
                        parent, false));
            case ROW_TYPE_RECEIVER:
                return new ReceiverMsgViewHolder(mLayoutInflater.inflate(R.layout
                        .row_receiver_msg, parent, false));
            default:
                return null;
        }
    }

    @Override
    public void onBindViewHolder(RecyclerView.ViewHolder holder, int position) {
        switch (getItemViewType(position)) {
            case ROW_TYPE_LOAD_EARLIER_MESSAGES:
                LoadEarlierMsgsViewHolder loadEarlierMsgsViewHolder =
                        (LoadEarlierMsgsViewHolder) holder;
                if (isLoadEarlierMsgs) {
                    loadEarlierMsgsViewHolder.btLoadEarlierMessages
                            .setOnClickListener(new View.OnClickListener() {
                                @Override
                                public void onClick(View view) {
                                    if (mLoadEarlierMessages != null) {
                                        mLoadEarlierMessages.onLoadEarlierMessages();
                                    }
                                }
                            });
                } else {
                    loadEarlierMsgsViewHolder.btLoadEarlierMessages.setVisibility(View.GONE);
                }
                break;
            case ROW_TYPE_SENDER:
                SenderMsgViewHolder senderMsgViewHolder = (SenderMsgViewHolder) holder;
                // set data for your sender chat bubble
                break;
            case ROW_TYPE_RECEIVER:
                ReceiverMsgViewHolder receiverMsgViewHolder = (ReceiverMsgViewHolder) holder;
                // set data for your receiver chat bubble
                break;
        }
    }

    @Override
    public int getItemCount() {
        return userMessagesList.size() + 1;
    }

    @Override
    public int getItemViewType(int position) {
        if (position == 0) {
            return ROW_TYPE_LOAD_EARLIER_MESSAGES; // row load earlier messages
        } else if (userMessagesList.get(position - 1).getUser_id() == userId) {
            return ROW_TYPE_SENDER; // sender row;
        } else {
            return ROW_TYPE_RECEIVER; // receiver row;
        }
    }

    public interface LoadEarlierMessages {
        void onLoadEarlierMessages();
    }


    public void setLoadEarlierMsgs(boolean isLoadEarlierMsgs) {
        this.isLoadEarlierMsgs = isLoadEarlierMsgs;
    }

    static class LoadEarlierMsgsViewHolder extends RecyclerView.ViewHolder {

        @Bind(R.id.btLoadEarlierMsgs) Button btLoadEarlierMessages;

        public LoadEarlierMsgsViewHolder(View itemView) {
            super(itemView);
            ButterKnife.bind(this, itemView);
        }
    }

    static class SenderMsgViewHolder extends RecyclerView.ViewHolder {

        public SenderMsgViewHolder(View itemView) {
            super(itemView);
            ButterKnife.bind(this, itemView);
        }
    }

    static class ReceiverMsgViewHolder extends RecyclerView.ViewHolder {

        public ReceiverMsgViewHolder(View itemView) {
            super(itemView);
            ButterKnife.bind(this, itemView);
        }
    }
}

最后在您的 ChatActivity 和 Override onLoadEarlierMessages()方法

    /**
     * Created by Mukesh on 21/12/2015.
     */
    public class ChatActivity extends AppCompatActivity
            implements ChatListAdapter.LoadEarlierMessages {

       // getting users recent messages and init RecyclerView
       private void showUserMessages() {
        // initialising LayoutManager for RecyclerView and setting that to RecyclerView
        mLinearLayoutManager = new LinearLayoutManager(this);
        mLinearLayoutManager.setStackFromEnd(true); // to start the list from bottom
        rvChatsList.setLayoutManager(mLinearLayoutManager);

        // initialising RecyclerView Adapter and setting that to the RecyclerView
        mChatListAdapter = new ChatListAdapter(this, userId, userMessagesList);
        rvChatsList.setAdapter(mChatListAdapter);

        // getting count of friend/contact messages and toggling visibility of load more button accordingly
        int count = mDataBaseHandler.getCountOfMessages(contactId);
        if (count != 0) {
            if (count > Constants.MESSAGES_LIMIT_FOR_LOCAL_DATABASE) {
                mChatListAdapter.setLoadEarlierMsgs(true);
            } else {
                mChatListAdapter.setLoadEarlierMsgs(false);
            }
            userMessagesList.addAll(mDataBaseHandler.getAllMessagesOfContact(contactId));
            mChatListAdapter.notifyDataSetChanged();
        }

    }

        @Override
        public void onLoadEarlierMessages() {
            ArrayList<UserMessage> tempList = mDataBaseHandler
                    .getPreviousMessagesOfContact(contactId, userMessagesList.size());
            if (tempList.size() > 0) {
                if (tempList.size() < Constants.MESSAGES_LIMIT_FOR_LOCAL_DATABASE) {
                    mChatListAdapter.setLoadEarlierMsgs(false);
                }
                View v = rvChatsList.getChildAt(0);
                int top = (v == null) ? 0 : v.getTop();
                for (int i = 0; i < tempList.size(); i++) {
                    userMessagesList.add(0, tempList.get(i));
                }
                mChatListAdapter.notifyDataSetChanged();
                mLinearLayoutManager.scrollToPositionWithOffset(tempList.size(), top);
            } else {
                mChatListAdapter.setLoadEarlierMsgs(false);
            }
        }

    }

希望这会有所帮助.. !!

Hope this will help..!!

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