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[英]Keep recyclerView at bottom when already at bottom and new item is added
[英]The RecyclerView scrolls to downward when a new message is added
我有一個聊天應用程序。 我使用了 RecyclerView,並將 stackFromEnd true 和 reverseLayout false 設置為 LinearlayoutManager。 當在底部添加新消息時,我的意思是在列表末尾,recyclerView 開始自動向下滾動而不是向上滾動。 適配器由 notifyItemInserted() 通知。
預期行為:將新消息添加到列表時,它應該滾動到底部或向上。 任何幫助表示贊賞。 謝謝,
這是適配器:
class ChatMessagesListAdapter(
var chatMessages: ChatMessagesDataModel
) : RecyclerView.Adapter<RecyclerView.ViewHolder>() {
companion object {
// we set the header as 0 so we can add more types to the ConversationItem enum
private const val ITEM_TYPE_HEADER = 0
}
override fun getItemViewType(position: Int): Int {
return when {
chatMessages.hasMoreItems -> chatMessages.messages[position].getItemType()
position == 0 -> ITEM_TYPE_HEADER
else -> chatMessages.messages[position - 1].getItemType()
}
}
// return +1 to draw the header if there are no items to load
override fun getItemCount() = chatMessages.messages.size + getContentIndex()
override fun getItemId(position: Int): Long {
return position.toLong()
}
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): RecyclerView.ViewHolder {
val inflater = LayoutInflater.from(parent.context)
return when (viewType) {
ITEM_TYPE_HEADER -> {
MessagesHeaderViewHolder(inflater.inflate(R.layout.item_chat_messages_header,
parent, false))
}
ChatItemDataModel.TYPE_ADDED_USER,
ChatItemDataModel.TYPE_VIDEO_NOTIFICATION -> {
MessagesInfoViewHolder(inflater.inflate(R.layout.item_chat_messages_info,
parent, false))
}
else -> {
MessagesMessageViewHolder(inflater.inflate(R.layout.item_chat_messages_message,
parent, false))
}
}
}
override fun onBindViewHolder(holder: RecyclerView.ViewHolder, position: Int) {
(holder as? MessagesHeaderViewHolder)?.bind()
(holder as? MessagesMessageViewHolder)?.bind(position, chatMessages.messages[getRealPosition(position)])
(holder as? MessagesInfoViewHolder)?.bind(chatMessages.messages[getRealPosition(position)])
}
private fun getContentIndex() = if (chatMessages.hasMoreItems) {
0
} else {
1
}
private fun getRealPosition(position: Int) = if (chatMessages.hasMoreItems) {
position
} else {
position - 1
}
private fun notifyChanges() {
if (chatMessages.numberOfItemsInserted == chatMessages.messages.size || isPreview ||
chatMessages.hadPendingMessages) {
notifyDataSetChanged()
} else {
// +1 because of the header
notifyItemRangeInserted(chatMessages.insertionIndex + getContentIndex(),
chatMessages.numberOfItemsInserted)
}
}
fun updateConversation(newChatMessages: ChatMessagesDataModel) {
chatMessages = newChatMessages
notifyChanges()
}
fun updateMessage(newMessage: ChatItemDataModel, isRemote: Boolean) {
if (newMessage.message.hashIdentifier.isNullOrBlank()) {
addNewMessage(newMessage)
return
}
val messageIndex = chatMessages.messages.indexOfFirst { it.message.hashIdentifier == newMessage.message.hashIdentifier }
if (messageIndex != -1) {
val localMessage = chatMessages.messages[messageIndex]
chatMessages.messages[messageIndex] = newMessage
if (failedMessages.contains(localMessage.message.sid)) {
if (isRemote) {
failedMessages.remove(localMessage.message.sid)
}
notifyItemChanged(messageIndex + getContentIndex())
}
}
else {
addNewMessage(newMessage)
}
}
private fun addNewMessage(newMessage: ChatItemDataModel) {
val oldCount = chatMessages.messages.size
chatMessages.messages.add(newMessage)
notifyItemInserted(oldCount + getContentIndex())
}
fun addLocalMessage(
sharedPrefsStorage: SharedPrefsStorage,
message: String, imageUri: Uri?, hashIdentifier: String
) {
val userMessage = UserMessage(messageBody = message, firstName = sharedPrefsStorage.firstName,
lastName = sharedPrefsStorage.lastName, isFromLoggedUser = true, imageUri = imageUri,
hashIdentifier = hashIdentifier, files = null, reactions = null)
val newMessage = ChatItemDataModel(userMessage, sharedPrefsStorage.profileImageUrl, sharedPrefsStorage.userId.toString())
val oldCount = chatMessages.messages.size
chatMessages.messages.add(newMessage)
notifyItemRangeInserted(oldCount + getContentIndex(), 1)
}
....
}
這是片段:
class ChatRoomMessagesFragment : Fragment() {
@Inject
lateinit var sharedPrefsStorage: SharedPrefsStorage
private var adapter: ChatMessagesListAdapter? = null
......
override fun onMessagesReceived(chatMessages: ChatMessagesDataModel) {
if (adapter == null) {
adapter = ChatMessagesListAdapter(chatMessages)
adapter?.setHasStableIds(true)
binding.recyclerview.adapter = adapter
} else {
adapter?.updateConversation(chatMessages)
}
}
override fun onUserMessageRetrieved(newMessage: ChatItemDataModel, isRemote: Boolean) {
adapter?.updateMessage(newMessage, isRemote)
}
private fun setupUI() {
binding.apply {
recyclerview.apply {
layoutManager = LinearLayoutManager(requireContext()).apply {
reverseLayout = false
stackFromEnd = true
addOnScrollListener(object : RecyclerView.OnScrollListener() {
override fun onScrolled(recyclerView: RecyclerView, dx: Int, dy: Int) {
super.onScrolled(recyclerView, dx, dy)
showScrollToBottomButtonIfNeeded(findFirstCompletelyVisibleItemPosition())
}
})
}
addOnScrollListener(object : PaginationScrollListener(
layoutManager as LinearLayoutManager,
ScrollDirection.BOTTOM
) {
override fun loadMoreItems() {
presenter.loadMoreMessages()
}
override fun isLastPage() = !presenter.hasMoreItems()
override fun isLoading() = presenter.isLoadingInProgress()
})
// prevent the list from scrolling when the keyboard opens
addOnLayoutChangeListener { _, _, _, _, bottom, _, _, _, oldBottom ->
if (bottom < oldBottom) {
scrollChatToBottom()
}
}
}
....
adapter?.addLocalMessage(sharedPrefsStorage, message, imageUri, hashIdentifier)
presenter.sendMessage("", message, imageUri, hashIdentifier)
}
private fun scrollChatToBottom() {
binding.apply {
recyclerview.post {
recyclerview.smoothScrollToPosition(recyclerview.adapter?.itemCount ?: 0)
}
}
}
}
您可以使用下面的代碼以編程方式向下滾動
recyclerView.scrollToPosition(chatList.size() - 1);
如果上述方法不起作用,您也可以嘗試另一種解決方案
setStackFromEnd(true) or setReverseLayout(true)
假設您的適配器由稱為消息的對象填充,並且您有一個名為messageList
的數據源(可能是一個集合等),它被傳遞給您的適配器。 你可以這樣做:
int position = messageList.size() > 0 ? (messageList.size()-1) : 0;
mRecyclerView.smoothScrollToPosition(position);
只需確保您的適配器不是 null 並且實際上從 messageList 獲取數據,因為這是在您的活動/片段 class 中而不是在適配器 class 中。
yourAdapter.registerAdapterDataObserver(object : RecyclerView.AdapterDataObserver() {
override fun onItemRangeInserted(positionStart: Int, itemCount: Int) {
super.onItemRangeInserted(positionStart, itemCount)
this@EventDetails.binding.rvData.scrollToPosition(positionStart)
}
override fun onItemRangeChanged(positionStart: Int, itemCount: Int) {
super.onItemRangeChanged(positionStart, itemCount)
this@EventDetails.binding.rvData.scrollToPosition(positionStart)
}
})
我認為第一種方法可以使用其中一種方法,請嘗試避免您自己使用 DiffUtils 或 ListAdapter(回收器視圖的擴展)調用 notifyDataSetChange() 或 intemChange()
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