iOS动画进阶 - 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