当列数发生变化时,动画回收器查看网格

Question

我使用的是RecyclerView用GridLayoutManager.用户可以在2到4之间切换跨度计数,这将导致动画将每个单元格的内置翻译动画运行到其新位置.我到目前为止使用的代码是:

TransitionManager.beginDelayedTransition(moviesGridRecycler);
gridLayoutManager.setSpanCount(NEW_SPAN_COUNT);
adapter.notifyDataSetChanged();

这对我来说一直很好,但现在我需要为每个跨度计数设置不同的布局.为了支持这一点,我有两种视图类型RecyclerView,因为当移动到新的跨度计数时视图类型被更改,RecyclerView无法看到它是"相同"的内容,并且不运行默认的转换动画.

如果我启用布局转换,我会获得视图输入动画,而不是查看位置更改动画.两个跨度计数的单元格视图的宽度和高度均为match_parent和wrap_content.

作为替代方案,我尝试将所有新视图类型放在一起,只有一种视图类型.我有一个FrameLayout,它包含两个跨度计数的视图.在onBindViewHolder(),我只是切换子视图的可见性.这也导致没有动画.

我跟着这个帖子和这个,但无法解决我的问题.

完整代码:

    class ItemFragment : Fragment() {
    private var spanCount = 2
    lateinit var recyclerView: RecyclerView
    lateinit var button: Button

    override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?,
                              savedInstanceState: Bundle?): View? {
        val view = inflater.inflate(R.layout.fragment_item_list, container, false)
        recyclerView = view.findViewById(R.id.listView)
        recyclerView.apply {
            adapter = MyItemRecyclerViewAdapter(DummyContent.ITEMS, spanCount)
            layoutManager = GridLayoutManager(context, spanCount)
            addItemDecoration(RecyclerGridDecoration(context))
        }
        button = view.findViewById(R.id.toggle)
        button.setOnClickListener { onToggle() }

        return view
    }

    fun onToggle() {
        spanCount = if (spanCount == 2) 4 else 2
        TransitionManager.beginDelayedTransition(recyclerView)
        (recyclerView.layoutManager as GridLayoutManager).spanCount = spanCount
        (recyclerView.adapter!! as MyItemRecyclerViewAdapter).apply {
            span = spanCount
            notifyDataSetChanged()
        }
    }

}



class MyItemRecyclerViewAdapter(
        private val mValues: List<DummyItem>,
        var span: Int)
    : RecyclerView.Adapter<MyItemRecyclerViewAdapter.ViewHolder>() {


    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ViewHolder {
        if (viewType == 2) {
            val view = LayoutInflater.from(parent.context)
                    .inflate(R.layout.items_two, parent, false)
            return TwoViewHolder(view)
        } else {
            val view = LayoutInflater.from(parent.context)
                    .inflate(R.layout.items_four, parent, false)
            return FourViewHolder(view)
        }

    }

    override fun onBindViewHolder(holder: ViewHolder, position: Int) {
        val item = mValues[position]
        if (holder is TwoViewHolder) {
            holder.textTwo.text = item.content
        } else if (holder is FourViewHolder) {
            holder.textFour.text = item.content
        }
    }

    override fun getItemCount(): Int = mValues.size

    abstract inner class ViewHolder(mView: View) : RecyclerView.ViewHolder(mView)

    inner class TwoViewHolder(mView: View) : ViewHolder(mView) {
        val image: ImageView = mView.imageTwo
        val textTwo: TextView = mView.textTwo

    }

    inner class FourViewHolder(mView: View) : ViewHolder(mView) {
        val textFour: TextView = mView.textFour
    }

    override fun getItemViewType(position: Int): Int {
        return span
    }
}

Answer 1

我有一个解决方案可以解决您的问题，将您的切换功能更改为：

  fun onToggle() {
        spanCount = if (spanCount == 2) 4 else 2
        (recyclerView.adapter!! as MyItemRecyclerViewAdapter).apply {
            span = spanCount
            notifyDataSetChanged()
        }
recyclerView.post(object:Runnable {
  public override fun run() {
     TransitionManager.beginDelayedTransition(recyclerView)
        (recyclerView.layoutManager as GridLayoutManager).spanCount = spanCount
  }
})
   }

在上面的代码中，我们首先更改了recyclerView的viewType，然后更改了RecyclerView UI Handler Queue上GridLayoutManager的spanCount，从而串行实现了两个UI操作。