RecyclerView 下降

Question

我有 RecyclerView 拖放功能，但我想在 Drop 上做一些计算。当我将 expensiveFunction() 放入 onMove() 时，它会在每次位置变化时触发，直到拖动结束。这是一个很大的矫枉过正。有没有办法在拖动结束时触发功能？

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

您可以覆盖 onSelectedChanged()，当 ViewHolder 被 ItemTouchHelper 滑动或拖动时调用它。

要捕捉掉落动作，请检查 actionState 值为 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")
        }
    }

}

RecyclerView 下降

RecyclerView on drop

android

kotlin

android-recyclerview

itemtouchhelper