Android回收站负载更多关于滚动顶
Android回收站负载更多关于滚动顶
提问于 2016-05-03 02:09:06
嘿，社区，我想做一个像聊天应用程序一样的RecyclerView。
我试过setStackFromEnd，效果很好。
final LinearLayoutManager llm = new LinearLayoutManager(getApplicationContext());
llm.setOrientation(LinearLayoutManager.VERTICAL);
llm.setStackFromEnd(true);在本教程的基础上加载更多代码，在教程的末尾，您应该会看到一个视频：回收站底部进度
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;
}
}
});所以我需要做一个像聊天应用程序一样的RecyclerView。堆栈从末端是完美的工作，但我需要触发加载更多的方法时，我去顶部，而不是下降。还可以在顶部而不是底部添加新的项目。提前谢谢。
回答 1
Stack Overflow用户
回答已采纳
发布于 2016-05-03 10:56:35
如果您只是想在顶部显示一个“加载早期消息”，则不需要使用onScrollListener。您可以简单地为加载更多的xml创建一个Button，将其作为RecyclerView的第一行，并创建一个Interface来处理单击事件。我正在发布来自我的一个项目的Adpater代码。希望这将有助于你得到一些想法，以进一步推进。
/**
* 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LoadEarlierMessages中实现ChatActivity侦听器，并在Override中实现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);
}
}
}希望这会有帮助！
页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/36994472
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