Question

一个人如何正确地将数据发送到adapter中的子fragment？我基本上是在尝试实现像评论区这样的Instagram，例如一堆评论，每个评论可以有更多评论（回复）。

为此，我使用一个main recyclerView + main adapter，这些实例保留在我的片段中，并在主适配器中绑定子注释（recyclerView + {{1 }}。

在主适配器中添加注释很容易，因为该对象在片段中始终可用，所以我只调用adapter：

MainAdapter

mainAdapter.addComments(newComments)

但是如何调用一个特定嵌套rV的fun addComments(newComments: List<Comment>){ comments.addAll( 0, newComments) //loading comments or previous comments go to the beginning notifyItemRangeInserted(0, newComments.size) }？我读到我不应该保存适配器实例，而只能使用位置。我正在尝试在片段中执行以下操作：

addComments

但是效果不是很好：由于我们只有RecyclerViews，因此如果用户在发布或获取项目后滚动，则特定的ViewHolder通常已经被回收，这会导致NullPointerException。因此，第一个问题是：如何与嵌套的recyclerviews及其适配器进行正确的交互？如果答案是通过Interface，请提供一个示例，因为我不尝试保存适配器，因此尝试失败了对象。

Answer 1

您可以通过放置注释使用单个多视图类型适配器来实现作为父项的一部分，您可以将子项添加到父项下面，并调用notifyItemRangeInserted。

这样，您就不必处理大多数回收问题。

要更新评论时，只需更新父项中的评论并调用notifyItemChanged。

如果需要，我创建了一个library，可以在编译时为您生成该代码。它支持您想要的确切案例以及更多其他内容。

Answer 2

使用@Gil Goldzweig的建议，这就是我的工作：如果Instagram像带评论的评论系统那样，我确实使用了嵌套的recyclerView系统。它只是使添加和删除项目变得更加容易。但是，关于问题如何正确地将数据片段发送到子适配器？，您却没有。它变得超级混乱。从片段中，我将数据发送到了mainAdapter，后者又将数据发送到了相关的childAdapter。使其平滑的关键是在向mainAdapter添加评论时使用notifyItemRangeInserted，然后在对评论添加回复时使用notifyItemChanged。第二个事件将允许使用payload将数据发送到子适配器。这是其他人感兴趣的代码：

片段

class CommentsFragment : androidx.fragment.app.Fragment(), Injectable,
    SendCommentButton.OnSendClickListener, CommentsAdapter.Listener {


@Inject
lateinit var viewModelFactory: ViewModelProvider.Factory

private val viewModel by lazy {
    ViewModelProviders.of(requireActivity(), viewModelFactory).get(CommentsViewModel::class.java)
}
private val searchViewModel by lazy {
    ViewModelProviders.of(requireActivity(), viewModelFactory).get(SearchViewModel::class.java)
}

private val mAdapter = CommentsAdapter(this)
private var contentid: Int = 0 //store the contentid to process further posts or requests for more comments
private var isLoadingMoreComments: Boolean = false //used to check if we should fetch more comments


override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?,
                          savedInstanceState: Bundle?): View? {


    return inflater.inflate(R.layout.fragment_comments, container, false)

}

override fun onActivityCreated(savedInstanceState: Bundle?) {
    super.onActivityCreated(savedInstanceState)

    //hide the action bar
    activity?.findViewById<BottomNavigationView>(R.id.bottomNavView)?.visibility = View.GONE


    contentid = arguments!!.getInt("contentid") //argument is mandatory, since comment is only available on content

    ivBackArrow.setOnClickListener{ activity!!.onBackPressed() }

    viewModel.initComments(contentid) //fetch comments

    val layoutManager = LinearLayoutManager(this.context)
    layoutManager.stackFromEnd = true
    rVComments.layoutManager = layoutManager
    mAdapter.setHasStableIds(true)
    rVComments.adapter = mAdapter



    setupObserver() //observe initial comments response
    setupSendCommentButton()
    post_comment_text.setSearchViewModel(searchViewModel)
    setupScrollListener(layoutManager) //scroll listener to load more comments

    iVCancelReplyTo.setOnClickListener{
        //reset ReplyTo function
        resetReplyLayout()
    }


}

private fun loadMoreComments(){
    viewModel.fetchMoreComments(contentid, mAdapter.itemCount)
    setupObserver()
}

/*
1.check if not already loading
2.check scroll position 0
3.check total visible items != total recycle items
4.check itemcount to make sure we can still make request
 */
private fun setupScrollListener(layoutManager: LinearLayoutManager){
    rVComments.addOnScrollListener(object: RecyclerView.OnScrollListener(){
        override fun onScrolled(recyclerView: RecyclerView, dx: Int, dy: Int) {
            super.onScrolled(recyclerView, dx, dy)
            val visibleItemCount = rVComments.childCount
            val totalItemCount = layoutManager.itemCount
            val pos = layoutManager.findFirstCompletelyVisibleItemPosition()
            if(!isLoadingMoreComments && pos==0 && visibleItemCount!=totalItemCount && mAdapter.itemCount%10==0){
                //fetch more comments
                isLoadingMoreComments = true
                loadMoreComments()
            }
        }

    })
}





private fun setupSendCommentButton() {
    btnSendComment.setOnSendClickListener(this)
}

override fun onSendClickListener(v: View?) {
    if(isInputValid(post_comment_text.text.toString())) {
        val isReply = mAdapter.commentid!=null
        viewModel.postComment(post_comment_text.text.toString(), mAdapter.commentid?: contentid, isReply) //get reply ID, otherwise contentID
        observePost()
        post_comment_text.setText("")
        btnSendComment.setCurrentState(SendCommentButton.STATE_DONE)
    }
}

override fun postCommentAsReply(username: String) {
    //main adapter method to post a reply
    val replyText = "${getString(R.string.replyingTo)} $username"
    tVReplyTo.text = replyText
    layoutReplyTo.visibility=View.VISIBLE
    post_comment_text.requestFocus()
}

override fun fetchReplies(commentid: Int, commentsCount: Int) {
    //main adapter method to fetch replies
    if(!isLoadingMoreComments){ //load one series at a time
        isLoadingMoreComments = true
        viewModel.fetchReplies(commentid, commentsCount)
        viewModel.replies.observe(this, Observer<Resource<List<Comment>>> {
            if (it?.data != null) when (it.status) {
                Resource.Status.LOADING -> {
                    //showProgressBar(true)
                }
                Resource.Status.ERROR -> {
                    //showProgressBar(false)
                    isLoadingMoreComments = false
                }
                Resource.Status.SUCCESS -> {
                    isLoadingMoreComments = false
                    mAdapter.addReplies(mAdapter.replyCommentPosition!!, it.data)
                    rVComments.scrollToPosition(mAdapter.replyCommentPosition!!)
                }
            }
        })
    }

}


private fun isInputValid(text: String): Boolean = text.isNotEmpty()

private fun observePost(){
    viewModel.postComment.observe(this, Observer<Resource<PostCommentResponse>> {
        if (it?.data != null) when (it.status) {
            Resource.Status.LOADING -> {
                //showProgressBar(true)
            }
            Resource.Status.ERROR -> {
                //showProgressBar(false)
            }
            Resource.Status.SUCCESS -> {
                if(it.data.asReply){
                    //dispatch comment to child adapter via main adapter
                    mAdapter.addReply(mAdapter.replyCommentPosition!!, it.data.comment)
                    rVComments.scrollToPosition(mAdapter.replyCommentPosition!!)
                }else{
                    mAdapter.addComment(it.data.comment)
                }
                resetReplyLayout()
                //showProgressBar(false)
            }
        }
    })
}



private fun setupObserver(){
    viewModel.comments.observe(this, Observer<Resource<List<Comment>>> {
        if (it?.data != null) when (it.status) {
            Resource.Status.LOADING -> {
                //showProgressBar(true)
            }
            Resource.Status.ERROR -> {
                isLoadingMoreComments = false
                //showProgressBar(false)
            }
            Resource.Status.SUCCESS -> {
                mAdapter.addComments(it.data)
                isLoadingMoreComments = false
                //showProgressBar(false)
            }
        }
    })
}

private fun resetReplyLayout(){
    layoutReplyTo.visibility=View.GONE
    mAdapter.replyCommentPosition = null
    mAdapter.commentid = null
}



override fun onStop() {
    super.onStop()
    activity?.findViewById<BottomNavigationView>(R.id.bottomNavView)?.visibility = View.VISIBLE
}

}

MainAdapter

class CommentsAdapter(private val listener: Listener) : RecyclerView.Adapter<CommentsAdapter.ViewHolder>(), ChildCommentsAdapter.ChildListener {

//method from child adapter
override fun postChildReply(replyid: Int, username: String, position: Int) {
    commentid = replyid
    replyCommentPosition = position
    listener.postCommentAsReply(username)
}

interface Listener {
    fun postCommentAsReply(username: String)
    fun fetchReplies(commentid: Int, commentsCount: Int=0)
}


class ViewHolder(val view: View) : RecyclerView.ViewHolder(view)

private var comments = mutableListOf<Comment>()
private var repliesVisibility = mutableListOf<Boolean>() //used to store visibility state for replies
var replyCommentPosition: Int? = null //store the main comment's position
var commentid: Int? = null //used to indicate which comment is replied to



override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ViewHolder {
   val view = LayoutInflater.from(parent.context)
           .inflate(R.layout.item_comment, parent, false)

    return ViewHolder(view)
}

override fun onBindViewHolder(holder: ViewHolder, position: Int) {

    val comment = comments[position]

    with(holder.view) {
        //reset visibilities (rebinding purpose)
        rVReplies.visibility = View.GONE
        iVMoreReplies.visibility = View.GONE
        tVReplies.visibility = View.GONE

        content.loadUserPhoto(comment.avatarThumbnailURL)
        text.setCaptionText(comment.username!!, comment.comment)
        tvTimestamp.setTimeStamp(comment.timestamp!!)

        val child = ChildCommentsAdapter(
            //we pass parent commentid and position to child to be able to pass it again on click
            this@CommentsAdapter, comments[holder.adapterPosition].id!!, holder.adapterPosition
        )
        val layoutManager = LinearLayoutManager(this.context)
        rVReplies.layoutManager = layoutManager
        rVReplies.adapter = child


        //initial visibility block when binding the viewHolder
        val txtMore = this.resources.getString(R.string.show_more_replies)
        if(comment.repliesCount>0) {
            tVReplies.visibility = View.VISIBLE
            if (repliesVisibility[position]) {
                //replies are to be shown directly
                rVReplies.visibility = View.VISIBLE
                child.addComments(comment.replies!!)
                tVReplies.text = resources.getString(R.string.hide_replies)

                if (comment.repliesCount > comment.replies!!.size) {
                    //show the load more replies arrow if we can fetch more replies
                    iVMoreReplies.visibility = View.VISIBLE
                }
            } else {
                //replies all hidden
                val txt = txtMore + " (${comment.repliesCount})"
                tVReplies.text = txt
            }
        }

        //second visibility block when toggling with the show more/hide textView
        tVReplies.setOnClickListener{
            //toggle child recyclerView visibility and change textView text
            if(holder.view.rVReplies.visibility == View.GONE){
                //show stuff
                if(comment.replies!!.isEmpty()){
                    Timber.d(holder.adapterPosition.toString())
                    //fetch replies if none were fetched yet
                    replyCommentPosition = holder.adapterPosition
                    listener.fetchReplies(comments[holder.adapterPosition].id!!)
                }else{
                    //load comments into adapter if not already
                    if(comment.replies!!.size>child.comments.size){child.addComments(comment.replies!!)}
                }

                repliesVisibility[position] = true
                holder.view.rVReplies.visibility = View.VISIBLE
                holder.view.tVReplies.text = holder.view.resources.getString(R.string.hide_replies)
                if (comment.repliesCount > comment.replies!!.size && comment.replies!!.isNotEmpty()) {
                    //show the load more replies arrow if we can fetch more replies
                    iVMoreReplies.visibility = View.VISIBLE
                }
            }else{
                //hide replies and change text
                repliesVisibility[position] = false
                holder.view.rVReplies.visibility = View.GONE
                holder.view.iVMoreReplies.visibility = View.GONE
                val txt = txtMore + " (${comment.repliesCount})"
                holder.view.tVReplies.text = txt
            }
        }



        tvReply.setOnClickListener{
            replyCommentPosition = holder.adapterPosition
            commentid = comments[holder.adapterPosition].id!!
            listener.postCommentAsReply(comments[holder.adapterPosition].username!!)
        }

        iVMoreReplies.setOnClickListener{
            replyCommentPosition = holder.adapterPosition
            listener.fetchReplies(comments[holder.adapterPosition].id!!, layoutManager.itemCount) //pass amount of replies too
        }


    }
}

@Suppress("UNCHECKED_CAST")
override fun onBindViewHolder(holder: ViewHolder, position: Int, payloads: MutableList<Any>) {
    if(payloads.isNotEmpty()){
        //add reply to child adapter
        with(holder.view){
            Timber.d(payloads.toString())
            val adapter = rVReplies.adapter as ChildCommentsAdapter
            if(payloads[0] is Comment){
                adapter.addComment(payloads[0] as Comment)
            }else{
                //will be of type List<Comment>
                adapter.addComments(payloads[0] as List<Comment>)
                val comment = comments[position]
                if (comment.repliesCount > comment.replies!!.size) {
                    //show the load more replies arrow if we can fetch more replies
                    iVMoreReplies.visibility = View.VISIBLE
                }else{
                    iVMoreReplies.visibility = View.GONE
                }
            }
        }
    }else{
        super.onBindViewHolder(holder,position, payloads) //delegate to normal binding process
    }
}


override fun getItemCount(): Int = comments.size


//add multiple replies to child adapter at pos 0
fun addReplies(position: Int, newComments: List<Comment>){
    comments[position].replies!!.addAll(0, newComments)
    notifyItemChanged(position, newComments)
}

//add a single reply to child adapter at last position
fun addReply(position: Int, newComment: Comment){
    comments[position].replies!!.add(newComment)
    comments[position].repliesCount += 1 //update replies count in case viewHolder gets rebinded
    notifyItemChanged(position, newComment)
}

//add a new comment to main adapter at last position
fun addComment(comment: Comment){
    comments.add(comment) //new comment just made goes to the end
    repliesVisibility.add(false)
    notifyItemInserted(itemCount-1)
}

//add multiple new comments to main adapter at pos 0
fun addComments(newComments: List<Comment>){
    comments.addAll( 0, newComments) //loading comments or previous comments go to the beginning
    repliesVisibility.addAll(0, List(newComments.size) { false })
    notifyItemRangeInserted(0, newComments.size)
}



}

childAdapter非常基础，逻辑几乎为零。

Android如何与片段中的嵌套recyclerView进行交互

2 个答案: