swift scorllView/collectionView 只滑动一个

查了很多方法都不太行
最后在一个scorllView的协议上看到了希望，实验之后成功了。

   var page = 0
    var oldX = 0.0
 //MARK: 控制每次只能滑动一个 减少滑动距离
    func scrollViewWillEndDragging(_ scrollView: UIScrollView, withVelocity velocity: CGPoint, targetContentOffset: UnsafeMutablePointer) {
        
        //print("targetContentOffset.pointee.x == ",targetContentOffset.pointee.x)
        
        if  oldX < targetContentOffset.pointee.x {
            //右滑
            if self.page >=  self.imageArr.count {
                page = self.imageArr.count - 1
            }else{
                page = page + 1
            }
            targetContentOffset.pointee.x = CGFloat(page) * (kScreenWidth - 70 + 20)
        } else {
            //左滑
            if self.page > 1 {
                page = page - 1
            }else{
                page = 0
            }
            //kScreenWidth - 70 + 20   item 大小 加上 边界
            targetContentOffset.pointee.x = CGFloat(page) * (kScreenWidth - 70 + 20)
        }
        
        oldX = targetContentOffset.pointee.x
    }