android - E/RecyclerView : No adapter attached; skipping layout in Android, Kotlin

Question

我已使用 Refrofit，MVVM，DataBinding，协程和 Kotlin 在我的应用程序中实现了RecyclerView。相同的代码在另一个片段中可以正常工作，但在此处不行。
*注意:翻新功能可以成功返回commentsList，但唯一的问题是在recyclerView中显示列表。

  override fun onActivityCreated(savedInstanceState: Bundle?) {
    super.onActivityCreated(savedInstanceState)
    val api = ApiRepository()
    factory = CommentsViewModelFactory(api)
    viewModel = ViewModelProvider(this, factory).get(CommentsViewModel::class.java)
    viewModel.getComments(requireActivity())
    viewModel.commentsList.observe(viewLifecycleOwner, Observer { comments ->
        rvComment.also {
            it.layoutManager = LinearLayoutManager(requireContext())
            it.setHasFixedSize(true)
            if (comments != null) {
                it.adapter = HomeServicesCommentsAdapter(comments, this)
            } 
        }

    })
}

ViewModel看起来像这样，我将注释声明为MutableLiveData，它成功返回了数据，但唯一的问题是适配器附件。

class CommentsViewModel(private val repository: ApiRepository) : ViewModel() {
var userComment: String? = null

private val comments = MutableLiveData<List<Comment>>()
private lateinit var job: Job

val commentsList: MutableLiveData<List<Comment>>
    get() = comments

fun getComments(context: Context) {
    job = CoroutinesIO.ioThenMain(
        {
            repository.getServices(context)
        }, {
            for (i in it!!.data.data)
                comments.value = i.comments
        }


    )
}

这是适配器的实现

class HomeServicesCommentsAdapter(
    private val comments: List<Comment>,
    private val listenerService: RvListenerServiceComments
) : RecyclerView.Adapter<HomeServicesCommentsAdapter.ServicesViewHolder>() {

    override fun getItemCount() = comments.size


    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int) =
        ServicesViewHolder(
            DataBindingUtil.inflate(
                LayoutInflater.from(parent.context),
                R.layout.custom_comment_layout,
                parent,
                false
            )
        )

    override fun onBindViewHolder(holder: ServicesViewHolder, position: Int) {
        holder.recyclerViewServicesBinding.comments = comments[position]
        notifyDataSetChanged()
    }

    class ServicesViewHolder(
        val recyclerViewServicesBinding: CustomCommentLayoutBinding
    ) : RecyclerView.ViewHolder(recyclerViewServicesBinding.root)

}

让我知道您是否需要xml布局文件。

Answer 1

与其在观察数据时在运行时提供布局管理器，不如说是，
在xml内定义layoutmanager
例如:

<androidx.recyclerview.widget.RecyclerView
                    android:id="@+id/rvNews"
                    android:layout_width="match_parent"
                    android:layout_height="wrap_content"
                    android:nestedScrollingEnabled="false"
                    tools:listitem="@layout/item_your_layout"
                    app:layoutManager="androidx.recyclerview.widget.LinearLayoutManager" />

从观察者中删除以下几行

it.layoutManager = LinearLayoutManager(requireContext())

编辑:
观察数据时不要创建适配器实例，因为观察数据不在MainThread上，因此请确保在 MainThread上设置数据

val adapter = HomeServicesCommentsAdapter(arrayListOf(), this)
        rvComment?.adapter = adapter
        viewModel.getComments(requireActivity())
        viewModel.commentsList.observe(viewLifecycleOwner, Observer { comments ->
                    comments?.let{adapter.setData(comments)}//define setData(list:ArrayList<Comments>) method in your adapter 
               
        })

HomeServicesCommentsAdapter.kt:

........
private var mObjects: MutableList<Comment>? = ArrayList()// top level declaration

fun setData(objects: List<Comment>?) {
        this.mObjects = objects as MutableList<Comment>
        this.notifyDataSetChanged()
    }
......