如何刷新 RecyclerView + PagedListAdapter 并滚动到顶部？

Question

我有一个RecyclerView，它正在使用PagedListAdapter。我想刷新列表（即从我的DataSource 获取数据）并自动滚动到顶部。

这是我的 RecyclerView：

    <android.support.v7.widget.RecyclerView
        android:id="@+id/recyclerView"
        android:layout_width="match_parent"
        android:layout_height="match_parent" />

    val adapter by lazy {
        DiscoveryListAdapter(activity)
    }

        recyclerView.let {
            it.adapter = adapter
            it.layoutManager = LinearLayoutManager(activity)
        }

这是我的适配器：

class DiscoveryListAdapter() : PagedListAdapter<Discovery, DiscoveryListItemViewHolder>(DiscoveryDiffCallback()) {

    @SuppressLint("CheckResult")
    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): DiscoveryListItemViewHolder {
        //Extension function
        val view = parent.inflate(R.layout.discovery_detail_list_item)
        return DiscoveryListItemViewHolder(view)
    }

    override fun onBindViewHolder(viewHolder: DiscoveryListItemViewHolder, position: Int) {
        getItem(position)?.let {
            viewHolder.populateFrom(it)
        }
    }

    class DiscoveryDiffCallback : DiffUtil.ItemCallback<Discovery>() {
        override fun areItemsTheSame(one: Discovery, two: Discovery) =
                one == two

        override fun areContentsTheSame(one: Discovery, two: Discovery) =
                one == two
    }
}

我正在像这样构建 PagedList，订阅返回的 LiveData 对象并在适配器上调用 submitList：

    fun buildLivePagedList(): LiveData<PagedList<Discovery>> {
        val config = PagedList.Config.Builder()
                .setPageSize(PAGE_SIZE)
                .setEnablePlaceholders(false)
                .setPrefetchDistance(PAGE_SIZE * 2)
                .build()
        val factory = DiscoveryListDataSourceFactory()
        return LivePagedListBuilder(factory, config).build()
    }

我正在使用这一行来刷新列表：

adapter.currentList?.dataSource?.invalidate()

这似乎正确刷新，但它使列表向下滚动一半。从那里我不知道如何让 recyclerview 返回到列表的顶部。我试过recyclerView.scrollToPosition(0)，但没有骰子。无论如何，列表都会刷新但不会滚动到顶部。我该怎么做？

Answer 1

尝试使用以下代码滚动到顶部：

pagedListAdapter.registerAdapterDataObserver(object : RecyclerView.AdapterDataObserver() {
    override fun onItemRangeInserted(positionStart: Int, itemCount: Int) {
        if (positionStart == 0) {
            manager.scrollToPosition(0)
        }
    }
})

Answer 2

class DiscoveryDiffCallback : DiffUtil.ItemCallback<Discovery>() {
    override fun areItemsTheSame(one: Discovery, two: Discovery) = false

    override fun areContentsTheSame(one: Discovery, two: Discovery) = false
}

让你的 ItemCallback 返回 false。希望有帮助！

Answer 3

    recyclerViewAdapter.currentList?.dataSource?.invalidate()

    recyclerView.postDelayed({
        recyclerView.layoutManager?.scrollToPosition(0)
    }, 400)

Answer 4

试试adapter.refresh()

 val movieListAdapter : PagingDataAdapter
    swiperefresh.setOnRefreshListener {
                movieListAdapter.refresh()
                swiperefresh.isRefreshing = false
    }