kotlin + 列表拖拽重新排序、滑动进行删除

//kotlin 如果内部类需要访问外部类数据 则要声明为inner
  inner class ItemDragHelperCallback : ItemTouchHelper.Callback() {
      /**
       * 获取可以拖动的方向标志
       * */
      override fun getMovementFlags(recyclerView: RecyclerView?, viewHolder: RecyclerView.ViewHolder?): Int {
          //此处返回可以拖动的方向值
          var swipe = 0
          var move = 0
          //此处为 假设recyclerview 不为空
          recyclerView?.let {
              if (recyclerView.layoutManager is GridLayoutManager) {
                  //如果是网格型 则可以左右上下都可以拖动
                  move = ItemTouchHelper.UP or ItemTouchHelper.DOWN or ItemTouchHelper.LEFT or ItemTouchHelper.RIGHT
              } else if (recyclerView.layoutManager is LinearLayoutManager) {
                  //支持上下拖动
                  move = ItemTouchHelper.UP or ItemTouchHelper.DOWN
                  //左右滑动删除
                  swipe = ItemTouchHelper.START or ItemTouchHelper.END
              }
          }
          return ItemTouchHelper.Callback.makeMovementFlags(move, swipe)
      }

      override fun onMove(recyclerView: RecyclerView?, viewHolder: RecyclerView.ViewHolder?, target: RecyclerView.ViewHolder?): Boolean {
          //此处的返回值 决定是否可以拖动
          if (viewHolder != null && target != null) {
              //此处不让标题来进行拖动效果 也就是拖动时 标题不会动
              if (viewHolder.itemViewType == TYPE_TITLE || target.itemViewType == TYPE_TITLE) {
                  return false
              }

              val fromPos = viewHolder.adapterPosition
              val toPos = target.adapterPosition
              //此处为mData不为空时
              mData?.let {
                  val from = mData[fromPos]
                  mData.removeAt(fromPos)
                  mData.add(toPos, from)
                  //执行交换动画
                  notifyItemMoved(fromPos, toPos)
                  return true
              }
          }
          //默认不让拖动
          return false
      }

      override fun onSwiped(viewHolder: RecyclerView.ViewHolder?, direction: Int) {
          //用于执行滑动删除
      }

      //不重写默认是返回true的 如果返回false的话 需要使用ItemTouchHelper的实例方法
      //使用 startDrag 来执行拖拽
      //使用 startSwipe 来执行滑动删除
      override fun isLongPressDragEnabled(): Boolean {
          return true
      }

      //是否支持滑动功能
      override fun isItemViewSwipeEnabled(): Boolean {
          return true
      }

      /**
       * 此处用于状态变化时 更换图片状态
       * */
      override fun onSelectedChanged(viewHolder: RecyclerView.ViewHolder?, actionState: Int) {
          super.onSelectedChanged(viewHolder, actionState)
          if (actionState != ItemTouchHelper.ACTION_STATE_IDLE) {
              //显示遮罩
              viewHolder?.let {
                  if (viewHolder is ItemViewHolder) {
                      viewHolder.mShadow!!.visibility = View.VISIBLE
                  }
              }
          }
      }

      /**
       * 此处当拖拽完成
       * */
      override fun clearView(recyclerView: RecyclerView?, viewHolder: RecyclerView.ViewHolder?) {
          super.clearView(recyclerView, viewHolder)
          //隐藏遮罩
          viewHolder?.let {
              if (viewHolder is ItemViewHolder) {
                  viewHolder.mShadow!!.visibility = View.GONE
              }
          }
      }

  }

//开始执行滑动
ItemTouchHelper.startSwipe(RecyclerView.ViewHolder)
//开始执行拖拽
ItemTouchHelper.startDrag(RecyclerView.ViewHolder)

 //将recyclerView依附到触摸辅助类
 open fun attachiToRecyclerView(recyclerView: RecyclerView) {
     if (mItemTouchHelper != null && recyclerView != null) {
         mItemTouchHelper.attachToRecyclerView(recyclerView)
     }
 }