import UIKit
var imageView:UIImageView!
class ViewController: UIViewController {
    override func viewDidLoad() {
        super.viewDidLoad()
        //创建ImageView
        imageView = UIImageView(frame: CGRect(x: 150, y: 250, width: 100, height: 100))
        //设置ImageView显示的图片
        imageView.image = UIImage(named: "image")
         //从文件目录中获取图片
        let path = Bundle.main.path(forResource: "image", ofType: "png")//将图片拖至项目中，并输入其名称和图片格式
        let fileimage = UIImage(contentsOfFile: path!)
        imageView.image = fileimage
        //从网络地址获取图片
        let url = URL(string: "imageURL")//输入图片地址
        //从网络中获取数据流
        let data = try! Data(contentsOf: url!)
        //通过数据流初始化图片
        let urlImage = UIImage(data: data)
        imageView.image = urlImage
        //实现动画播放
        let image1 = UIImage(named: "image1")
        let image2 = UIImage(named: "image2")
        imageView.animationImages = [image1!,image2!]
        imageView.animationDuration = 0.1//设置图片变换间隔
        //设置图片比例
        imageView.contentMode = .scaleToFill//不保持原图比例，充满imageView
        imageView.clipsToBounds = true//将超出的部分裁剪掉
        /*
         scaleAspecFit 保持图片比例已合适的大小填充imageView
         scaleAspectFill//保持图片比例并填充满imageView
        */
        //将UIImageViewj添加到视图
        self.view.addSubview(imageView)
    }
    //view即将显示的监听
    override func viewWillAppear(_ animated: Bool) {
        super.viewWillAppear(animated)
        imageView.startAnimating()//开始播放
    }
    //view即将消失的监听
    override func viewWillDisappear(_ animated: Bool) {
        super.viewWillDisappear(animated)
        imageView.stopAnimating()//结束播放
    }
}