RecyclerView使用ItemTouchHelper拖动体验优化

[itlgl]

问题

在项目中使用发现，在上下拖动替换时，需要手机拖动条目到目标条目的上方才能完成替换，体验不太好

解决方式

解决方法是重写ItemTouchHelper.Callback的chooseDropTarget方法，自定义拖动识别逻辑

代码如下：

// 优化拖动替换体验，手指在目标控件中心点&&拖动控件覆盖了目标控件中心点，就进行替换
override fun chooseDropTarget(
    selected: RecyclerView.ViewHolder,
    dropTargets: MutableList<RecyclerView.ViewHolder>,
    curX: Int,
    curY: Int
): RecyclerView.ViewHolder? {
    var winner: RecyclerView.ViewHolder? = null
    val currCenterX = curX + selected.itemView.width / 2
    val currCenterY = curY + selected.itemView.height / 2
    val targetsSize = dropTargets.size
    for (i in 0 until targetsSize) {
        val target = dropTargets[i]
        val targetCenterX = target.itemView.right - target.itemView.width / 2
        val targetCenterY = target.itemView.bottom - target.itemView.height / 2
        if (currCenterX > target.itemView.left && currCenterX < target.itemView.right &&
            currCenterY > target.itemView.top && currCenterY < target.itemView.bottom &&
            targetCenterX > target.itemView.left && targetCenterX < target.itemView.right &&
            targetCenterY > target.itemView.top && targetCenterY < target.itemView.bottom
        ) {
            winner = target
        }
    }
    return winner
}