RecyclerView on drop

Question

我有RecyclerView拖放功能，但我想做一些计算onDrop。当我将我的expensiveFunction()放入onMove()时，它会在每次位置改变时触发，直到拖动结束。这太夸张了。有没有办法在拖拽端触发函数？

val itemTouchHelper = ItemTouchHelper(simpleCallback)
itemTouchHelper.attachToRecyclerView(recyclerView)

private var simpleCallback = object : ItemTouchHelper.SimpleCallback(ItemTouchHelper.UP.or(ItemTouchHelper.DOWN), 0) {
    override fun onMove(recyclerView: RecyclerView, viewHolder: RecyclerView.ViewHolder, target: RecyclerView.ViewHolder): Boolean {
        val startPosition = viewHolder.absoluteAdapterPosition
        val endPosition = target.absoluteAdapterPosition

        Collections.swap(itemList, startPosition, endPosition)
        recyclerView.adapter?.notifyItemMoved(startPosition, endPosition)

        expensiveFunction()

        return true
    }
}

Answer 1

您可以重写当ViewHolder被ItemTouchHelper滑动或拖动时调用的onSelectedChanged()。

要捕获删除操作，请检查将actionState值设置为ItemTouchHelper.ACTION_STATE_IDLE

override fun onSelectedChanged(viewHolder: RecyclerView.ViewHolder?, actionState: Int) {
    super.onSelectedChanged(viewHolder, actionState)
    when (actionState) {
        // when the item is dropped
        ItemTouchHelper.ACTION_STATE_IDLE -> {
            Log.d(TAG, "Item is dropped")
        }
    }

}