recyclerview 实现拖拽功能

本文主要是介绍recyclerview 实现拖拽功能，希望对大家解决编程问题提供一定的参考价值，需要的开发者们随着小编来一起学习吧！

recyclerview实现拖拽功能可以借助原生提供的ItemTouchHelpter类来实现，基础拖拽和删除功能都封装的有，细节需要自己处理下。

先定义一个接口，定义一下方法，方便和adapter联动处理数据，相对ItemTouchHelpter.call 增加一个判断当前所选item是否能够拖拽的判断。

interface RecyclerItemDragTouchHelper {/*** 交换** @param source* @param target*/fun onItemMove(source: RecyclerView.ViewHolder?, target: RecyclerView.ViewHolder?)/*** 选中** @param source*/fun onItemSelect(source: RecyclerView.ViewHolder?, actionState: Int)/*** 状态清除** @param source*/fun onItemClear(source: RecyclerView.ViewHolder?)/*** item是否可以拖拽** @param source*/fun isCanMove(position: Int): Boolean}

需要目标adapter 继承RecyclerItemDragTouchHelper接口实现接口中方法

  定义两个变量记录数据交换后要刷新的位置，避免出现混乱问题。   

var startPosition = -1
var endPosition = -1

 override fun onItemMove(source: RecyclerView.ViewHolder?, target: RecyclerView.ViewHolder?) {if (!isCanMove(source?.bindingAdapterPosition ?: 0)) returnif (!isCanMove(target?.bindingAdapterPosition ?: 0)) returnval fromPosition = source?.bindingAdapterPosition ?: 0val toPosition = target?.bindingAdapterPosition ?: 0if (fromPosition < items.size && toPosition < items.size) {Collections.swap(items, fromPosition, toPosition)notifyItemMoved(fromPosition, toPosition)}onItemClear(source)endPosition = toPosition}override fun onItemSelect(source: RecyclerView.ViewHolder?, actionState: Int) {if (!isCanMove(source?.layoutPosition ?: 0)) returnif (actionState != ACTION_STATE_IDLE) {source?.itemView?.scaleX = 1.2fsource?.itemView?.scaleY = 1.2f}if (source != null && actionState != ACTION_STATE_IDLE) {// 非闲置状态下，记录下起始 positionstartPosition = source.layoutPosition}if (actionState == ACTION_STATE_IDLE) {
// 只刷新交换两个以及中间数据 看自己需求
//            notifyItemRangeChanged(
//                startPosition.coerceAtMost(endPosition),
//                abs(startPosition - endPosition) + 1
//            )//全部刷新notifyItemRangeChanged(0,items.size-1)}}override fun onItemClear(source: RecyclerView.ViewHolder?) {source?.itemView?.scaleX = 1.0fsource?.itemView?.scaleY = 1.0f}//此方法判断某个viewholder是否指出拖拽override fun isCanMove(position: Int): Boolean = !items[position].isAdd()

主要还是得靠ItemTouchHelper实现，自定义一个类继承ItemTouchHelper.Callback，实现其方法，通过RecyclerItemDragTouchHelper与adapter 关联，这样方便处理。

class RecyclerItemDragTouchHelperCallback(private val helper: RecyclerItemDragTouchHelper ) :ItemTouchHelper.Callback() {override fun getMovementFlags(recyclerView: RecyclerView,viewHolder: RecyclerView.ViewHolder): Int {val dragFlags =ItemTouchHelper.UP or ItemTouchHelper.DOWN or ItemTouchHelper.LEFT or ItemTouchHelper.RIGHTreturn makeMovementFlags(if (helper.isCanMove(viewHolder.bindingAdapterPosition)) dragFlags else 0,0)}override fun onMove(recyclerView: RecyclerView,viewHolder: RecyclerView.ViewHolder,target: RecyclerView.ViewHolder): Boolean {helper.onItemMove(viewHolder, target)return true}override fun onSwiped(viewHolder: RecyclerView.ViewHolder, direction: Int) {}override fun isLongPressDragEnabled(): Boolean {return true}override fun isItemViewSwipeEnabled(): Boolean {return false}override fun clearView(recyclerView: RecyclerView, viewHolder: RecyclerView.ViewHolder) {super.clearView(recyclerView, viewHolder)if (!recyclerView.isComputingLayout) {helper.onItemClear(viewHolder)}}override fun onSelectedChanged(viewHolder: RecyclerView.ViewHolder?, actionState: Int) {super.onSelectedChanged(viewHolder, actionState)helper.onItemSelect(viewHolder,actionState)}
}

然后再绑定RecyclerView即可

// 适配器添加拖拽回调
val callback = RecyclerItemDragTouchHelperCallback(adapter)
val itemTouchHelper = ItemTouchHelper(callback)
// 为recyclerView添加拖拽功能
itemTouchHelper.attachToRecyclerView(binding.rvList)

这篇关于recyclerview 实现拖拽功能的文章就介绍到这儿，希望我们推荐的文章对编程师们有所帮助！

---