Day9 - ScrollView，图片缩小方法

效果图

效果图

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1、布局

结构如下

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2、然后设置ScrollView

 scrollView.addSubview(imageView)
        
        scrollView.autoresizingMask = [.FlexibleWidth, .FlexibleHeight]
        
        scrollView.zoomScale = scrollView.minimumZoomScale
        
        scrollView.delegate = self
        
        setZoomScaleFor(scrollView.frame.size)

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setZoomScaleFor...方法

 private func setZoomScaleFor(srollViewSize: CGSize) {
        
        let imageSize = imageView.bounds.size
        let widthScale = srollViewSize.width / imageSize.width
        let heightScale = srollViewSize.height / imageSize.height
        let minimunScale = min(widthScale, heightScale)
        
        scrollView.minimumZoomScale = minimunScale
        scrollView.maximumZoomScale = 3.0
        
    }

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添加三个属性

var top : CGFloat = 0
    
    var imageView : UIImageView = {
        let iv = UIImageView(image: UIImage(named: "item"))
        iv.sizeToFit()
        return iv
    }()
    
    var showImageView: UIImageView = {
        let iv = UIImageView(image: UIImage(named: "item"))
        iv.userInteractionEnabled = true
        return iv
    }()

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为showImageView添加手势，在ViewDidLoad中

let tap : UITapGestureRecognizer = UITapGestureRecognizer(target: self, action: #selector(ViewController.showScrollView))
        
        showImageView.addGestureRecognizer(tap)

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实现手势方法

 @objc private func showScrollView(){
        
        UIView.animateWithDuration(0.5, animations: { 
            self.showImageView.frame = self.scrollView.frame
            self.showImageView.frame.size.width = self.scrollView.contentSize.width
            }) { (completion) in
            self.scrollView.hidden = false
                self.showImageView.removeFromSuperview()
                self.top = 0
        }
    }

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实现scrollView的代理方法

 func scrollViewDidZoom(scrollView: UIScrollView) {
        
        top = scrollView.contentInset.top
        self.recenterImage()
        
    }
    
    func scrollViewDidEndZooming(scrollView: UIScrollView, withView view: UIView?, atScale scale: CGFloat) {
        
        if top >= 1 {
            scrollView.hidden = true
            showImageView.layoutMargins = scrollView.contentInset
            self.view.addSubview(showImageView)
            
            UIView.animateWithDuration(0.5, animations: {
                self.showImageView.frame = CGRect(x: 10, y: 20, width: 100, height: 100)
            })
        }
    }
    
    func viewForZoomingInScrollView(scrollView: UIScrollView) -> UIView? {
        if top > 1 {
            return nil
        }
        return self.imageView
    }

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最后通过recenterImage方法设置图片大小

 private func recenterImage() {
        
        let scrollViewSize = scrollView.bounds.size
        let imageViewSize = imageView.frame.size
        let horizontalSpace = imageViewSize.width < scrollViewSize.width ? (scrollViewSize.width - imageViewSize.width) / 2.0 : 0
        let verticalSpace = imageViewSize.height < scrollViewSize.height ? (scrollViewSize.height - imageViewSize.width) / 2.0 :0
        
        scrollView.contentInset = UIEdgeInsetsMake(verticalSpace, horizontalSpace, verticalSpace, horizontalSpace)
        
    }

Demo - ImageScrollEffect