苹果开发之一个简单的动画效果（方块来回反复移动）

import UIKit
 
class ViewController: UIViewController {
     
    // 方块
    var block1:UIView!
    var block2:UIView!
    var block3:UIView!
     
    override func viewDidLoad()
    {
        super.viewDidLoad()
         
        //创建方块
        block3 = UIView(frame:CGRectMake(0, 0, 15, 15))
        block3.center.y = self.view.bounds.height / 2 //方块垂直居中
        block3.backgroundColor = UIColor.darkGrayColor()
        self.view.addSubview(block3)
         
        block2 = UIView(frame:CGRectMake(0, 0, 20, 20))
        block2.center.y = self.view.bounds.height / 2 //方块垂直居中
        block2.backgroundColor = UIColor.darkGrayColor()
        self.view.addSubview(block2)
         
        block1 = UIView(frame:CGRectMake(0, 0, 25, 25))
        block1.center.y = self.view.bounds.height / 2 //方块垂直居中
        block1.backgroundColor = UIColor.darkGrayColor()
        self.view.addSubview(block1)
         
        //播放动画
        playAnimation()
    }
     
    //播放动画
    func playAnimation()
    {
        UIView.animateWithDuration(0.6, delay: 0.4, options: [.Repeat, .Autoreverse],
            animations: {
                self.block1.frame.origin.x =
                    self.view.bounds.width - self.block1.frame.width
            },
            completion: nil)
         
        UIView.animateWithDuration(0.6, delay: 0.45, options: [.Repeat, .Autoreverse],
            animations: {
                self.block2.frame.origin.x =
                    self.view.bounds.width - self.block2.frame.width
            },
            completion: nil)
         
        UIView.animateWithDuration(0.6, delay: 0.5, options: [.Repeat, .Autoreverse],
            animations: {
                self.block3.frame.origin.x =
                    self.view.bounds.width - self.block2.frame.width
            },
            completion: nil)
    }
     
    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
    }
}