iOS开发进阶 - 实现类似美颜相机的相机启动动画

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最近在写一个相册的demo，偶尔看到了美拍的相机过载动画觉得很有意思，就想在我的相册demo中加入一个这种特效，下面把我的想法和实现过程给大家分享一下

先上效果图：（demo地址）

步骤分析

这个动效看起来很有特色但是实现起来是非常简单的，只需要用到CALayer和CAShapeLayer做为展示层，然后通过CABasicAnimation实现动画就行了~

• 用两个CALayer来呈现启动的image
• 通过UIBezierPath和CAShapeLayer来画出具有曲线的CAShapeLayer
• 然后将曲线的CAShapeLayer做为CALayer的mask
• 最后通过CABasicAnimation做一个简单的位移动画

先绘制上半部分的layer

/**
     绘制上半部分的layer
     */
    private func configTopShapeLayer() {
        //绘制贝斯尔曲线
        let topBezier:UIBezierPath = UIBezierPath()
        topBezier.moveToPoint(CGPointMake(-1, -1))
        topBezier.addLineToPoint(CGPointMake(bounds.width+1, -1))
        topBezier.addCurveToPoint(CGPointMake(bounds.width/2.0+1, bounds.height/2.0+1), controlPoint1: CGPointMake(bounds.width+1, 0+1), controlPoint2: CGPointMake(343.5+1, 242.5+1))
        topBezier.addCurveToPoint(CGPointMake(-1, bounds.height+2), controlPoint1: CGPointMake(31.5+2, 424.5+2), controlPoint2: CGPointMake(0+2, bounds.height+2))
        topBezier.addLineToPoint(CGPointMake(-1, -1))
        topBezier.closePath()
        //创建一个CAShapeLayer，将绘制的贝斯尔曲线的path给CAShapeLayer
        let topShape = CAShapeLayer()
        topShape.path = topBezier.CGPath
        //给topLayer设置contents为启动图
        topLayer.contents = launchImage?.CGImage
        topLayer.frame = bounds
        layer.addSublayer(topLayer)
        //将绘制后的CAShapeLayer做为topLayer的mask
        topLayer.mask = topShape
    }

绘制后的结果是这样的：

然后以同样的原理绘制下半部分的layer

/**
     绘制下半部分的layer
     */
    private func configBottomShapeLayer() {
        //绘制贝斯尔曲线
        let bottomBezier:UIBezierPath = UIBezierPath()
        bottomBezier.moveToPoint(CGPointMake(bounds.width, 0))
        bottomBezier.addCurveToPoint(CGPointMake(bounds.width/2.0, bounds.height/2.0), controlPoint1: CGPointMake(bounds.width, 0), controlPoint2: CGPointMake(343.5, 242.5))
        bottomBezier.addCurveToPoint(CGPointMake(0, bounds.height), controlPoint1: CGPointMake(31.5, 424.5), controlPoint2: CGPointMake(0, bounds.height))
        bottomBezier.addLineToPoint(CGPointMake(bounds.width, bounds.height))
        bottomBezier.addLineToPoint(CGPointMake(bounds.width, 0))
        bottomBezier.closePath()
        //创建一个CAShapeLayer，将绘制的贝斯尔曲线的path给CAShapeLayer
        let bottomShape = CAShapeLayer()
        bottomShape.path = bottomBezier.CGPath
        //给bottomLayer设置contents为启动图
        bottomLayer.contents = launchImage?.CGImage
        bottomLayer.frame = bounds
        layer.addSublayer(bottomLayer)
        //将绘制后的CAShapeLayer做为bottomLayer的mask
        bottomLayer.mask = bottomShape
    }

这里注意的是画的贝斯尔曲线上半部分的要整体向下平移1到2个像素，为了防止贝斯尔曲线画曲线导致的锯齿效果，下面是下半部分完成后的效果图：

最后给两个layer一个位移动画

/**
     展开的动画
     */
    func starAnimation() {
        //创建一个CABasicAnimation作用于CALayer的anchorPoint
        let topAnimation = CABasicAnimation.init(keyPath: "anchorPoint")
        //设置移动路径
        topAnimation.toValue = NSValue.init(CGPoint: CGPointMake(1, 1))
        //动画时间
        topAnimation.duration = 0.6
        //设置代理，方便完成动画后移除当前view
        topAnimation.delegate = self
        //设置动画速度为匀速
        topAnimation.timingFunction = CAMediaTimingFunction.init(name: kCAMediaTimingFunctionLinear)
        //设置动画结束后不移除点，保持移动后的位置
        topAnimation.removedOnCompletion = false
        topAnimation.fillMode = kCAFillModeForwards
        topLayer.addAnimation(topAnimation, forKey: "topAnimation")

        //创建一个CABasicAnimation作用于CALayer的anchorPoint
        let bottomAnimation = CABasicAnimation.init(keyPath: "anchorPoint")
        //设置移动路径
        bottomAnimation.toValue = NSValue.init(CGPoint: CGPointMake(0, 0))
        //动画时间
        bottomAnimation.duration = 0.6
        //设置动画速度为匀速
        bottomAnimation.timingFunction = CAMediaTimingFunction.init(name: kCAMediaTimingFunctionLinear)
        //设置动画结束后不移除点，保持移动后的位置
        bottomAnimation.removedOnCompletion = false
        bottomAnimation.fillMode = kCAFillModeForwards
        bottomLayer.addAnimation(bottomAnimation, forKey: "topAnimation")
    }

        /**
     动画完成后移除当前view
     */
    internal override func animationDidStop(anim: CAAnimation, finished flag: Bool)           
    {
        if flag {
            removeFromSuperview()
        }
    }

这里为了方便观察，我将动画时间变长了，下面是完成后的效果图：

到这里这个动效就完成的差不多了，希望大家能学到东西，如果大家有更好的实现办法也可以给我提意见，我学习学习，谢谢大家观看，另外附加demo地址，喜欢的可以关注一下