Swift笔记 使用UIScrollView来居中显示图片，可缩放和跟踪触摸点

verride func touchesBegan(touches: Set<UITouch>, withEvent event: UIEvent?) {
let touch : UITouch! = touches.first
location = touch.locationInView(self)
TouchPointImg.center = location
}
override func touchesEnded(touches: Set<UITouch>, withEvent event: UIEvent?) {
let touch : UITouch! = touches.first
location = touch.locationInView(self)
if location.x<0 { location.x=0}
if location.y<0 { location.y=0}
if location.x > self.imageView.frame.width { location.x=self.imageView.frame.width}
if location.y > self.imageView.frame.height { location.y=self.imageView.frame.height}

TouchPointImg.center = location
}

@IBOutlet var scrollView: TouchScrollView!
//指向自定义类

需要设置
scrollView.userInteractionEnabled = true
还需要设置
scrollView.delegate         = self;
scrollView.minimumZoomScale = 1.0;
scrollView.maximumZoomScale = 4.0;
不然不能缩放