动画

介绍下iOS开发动画的几种方式吧：

一. 代码放在Begin和Commit之间：

[UIView beginAnimations:nil context:nil]; // 开始动画
// Code...
[UIView commitAnimations]; // 提交动画

e.g.

[UIView beginAnimations:nil context:nil]; // 开始动画
[UIView setAnimationDuration:10.0]; // 动画时长

/**
 *  图像向下移动
 */
CGPoint point = _imageView.center;
point.y += 150;
[_imageView setCenter:point];

[UIView commitAnimations]; // 提交动画

但这一方式好像是有些过时了，API文档最后面是这样写的：

Use of this method is discouraged in iOS 4.0 and later. You should use the block-based animation methods to specify your animations instead.

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二. Block

UIView类几个类方法用于实现相对简单的动画
e.g.

//准备工作
lazy var box:UIView = UIView()
.
.
.
self.view.addSubview(box)
box.backgroundColor = UIColor.red
box.snp.makeConstraints { (make) -> Void in
    make.width.height.equalTo(50)
    make.centerY.equalTo(self.view)
    make.left.equalTo(self.view.snp.left)
}

1. 基本动画

        UIView.animate(withDuration: 3) { 
            self.box.frame.origin.x = self.view.frame.width - 50
        }

2. 添加结束处理

        UIView.animate(withDuration: 3, animations: { 
            self.box.frame.origin.x = self.view.frame.width - 50
        }) { (isFinished) in
            if isFinished {
                UIView.animate(withDuration: 3, animations: { 
                    self.box.frame.origin.x = 0
                })
            }
        }

3. 添加动画配置

        UIView.animate(withDuration: 3, delay: 0.0, options: [.repeat,.autoreverse], animations: {
            self.box.frame.origin.x = self.view.frame.width - 50
        }) { (isFinished) in
            
        }

4. Spring动画

        UIView.animate(withDuration: 3, delay: 1, usingSpringWithDamping: 1.0, initialSpringVelocity: 5.0, options: .curveEaseIn, animations: {
            self.box.frame.origin.x = self.view.frame.width - 50
        }) { (isFinished) in
            
        }

5. 关键帧动画

    func doKeyFrameworkAnimation() {
        
        UIView.animateKeyframes(withDuration: 4.0, delay: 0.0, options: [.calculationModeCubic, .calculationModeLinear], animations: { 
            let colors:[UIColor] = [UIColor.black,UIColor.red,UIColor.blue,UIColor.yellow]
            let frames:[CGRect] = [CGRect.init(x: 0, y: 0, width: 20, height: 20),
                                   CGRect.init(x: 50, y: 50, width: 30, height: 30),
                                   CGRect.init(x: 100, y: 100, width: 40, height: 40),
                                   CGRect.init(x: 150, y: 150, width: 50, height: 50)]

            for index in 0 ..< colors.count {
                
                UIView.addKeyframe(withRelativeStartTime: Double(index)/Double(colors.count), relativeDuration: Double(1)/Double(colors.count), animations: {
                    self.box.backgroundColor = colors[index]
                    self.box.frame = frames[index]
                })
            }

        }) { (isFinished) in
            
        }   
    }

以上各方法说明与参数说明请参看文档。不复制，不翻译了😁

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三. Core Foundation(略)

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四. Lottie

Lottie Git
使用这个库以后，很多动画都让UED去做了。终于，开发不用再写动画了~！？🤔