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用UIScrollView产生视差效果

效果

SmoothStyle.gif

ReplaceStyle.gif

源码

MoreInfoView:

import UIKit

class MoreInfoView: UIView {

    var imageView: UIImageView?
    
    override init(frame: CGRect) {
        
        super.init(frame: frame)
        
        self.layer.borderWidth   = 0.5
        self.layer.borderColor   = UIColor.blackColor().CGColor
        self.layer.masksToBounds = true
        
        imageView = UIImageView(frame: frame)
        
        self.addSubview(imageView!)
    }

    required init?(coder aDecoder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }

}
  

ViewController:

import UIKit

// MARK: -ScrollView上ImageView的位移因子
enum SwitchFactor {
    
    // 平滑过渡
    case SmoothStyle
    
    // 交换过渡
    case ReplaceStyle
    
    // 以下皆是经验值,并非计算出来的
    func factor() -> CGFloat {
        
        switch self {
            
        case .SmoothStyle:
            
            return 1
            
        case .ReplaceStyle:
            
            return 2
        }
    }
}

class ViewController: UIViewController, UIScrollViewDelegate {
    
    var scrollView: UIScrollView?
    let viewWidth = UIScreen.mainScreen().bounds.width
    
    override func viewDidLoad() {
        
        super.viewDidLoad()
        
        view.backgroundColor = UIColor.blackColor()
        
        scrollView = UIScrollView(frame: view.bounds)
        scrollView?.delegate      = self
        scrollView?.pagingEnabled = true
        
        view.addSubview(scrollView!)
        
        let imageArray = [UIImage(named: "1"),UIImage(named: "2"),UIImage(named: "3"),UIImage(named: "4"),UIImage(named: "5")]
        
        for (index, value) in imageArray.enumerate() {
            
            let show = MoreInfoView(frame: CGRect(x: CGFloat(index) * view.bounds.size.width, y: 0, width: view.bounds.width, height: view.bounds.height))
            
            show.imageView?.image = value
            
            scrollView?.addSubview(show)
        }
        
        scrollView?.contentSize = CGSize(width: CGFloat(imageArray.count) * view.bounds.width, height: view.bounds.height)
    }
    
    // MARK: UIScrollViewDelegate
    func scrollViewDidScroll(scrollView: UIScrollView) {
        
        let x = scrollView.contentOffset.x
        
        for (index, value) in scrollView.subviews.enumerate() {
            
            if value.isKindOfClass(MoreInfoView.classForCoder()) {
                
                let temp = value as! MoreInfoView
                
                // 乘数因子
                let factor = SwitchFactor.ReplaceStyle
                
                // 产生视差效果
                var rect: CGRect = (temp.imageView?.frame)!
                rect.origin.x = factor.factor() * (x - CGFloat(index) * viewWidth)
                temp.imageView?.frame = rect
            }
            
        }
    }
    
    
}

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