上一篇博客分析了支付中动画的实现，本篇博客是分析支付完成的动画。

支付宝支付动画

一、动画解析

为了方便观察，放慢了动画的速度，并添加辅助线：

原理分析

通过上图可知，支付完成的动画由两部分组成：圆环动画 + 对号动画

二、代码实现

1、圆环动画

这个动画比较简单，是利用贝塞尔曲线画弧的功能。再利用CAShapeLayer的strokeEnd属性加上核心动画实现的圆环动画。

-(void)circleAnimation{
    
    //显示图层
    CAShapeLayer *circleLayer = [CAShapeLayer layer];
    circleLayer.frame = _animationLayer.bounds;
    [_animationLayer addSublayer:circleLayer];
    circleLayer.fillColor =  [[UIColor clearColor] CGColor];
    circleLayer.strokeColor  = BlueColor.CGColor;
    circleLayer.lineWidth = lineWidth;
    circleLayer.lineCap = kCALineCapRound;
    
    //运动路径
    CGFloat lineWidth = 5.0f;
    CGFloat radius = _animationLayer.bounds.size.width/2.0f - lineWidth/2.0f;
    UIBezierPath *path = [UIBezierPath bezierPathWithArcCenter:circleLayer.position radius:radius startAngle:-M_PI/2 endAngle:M_PI*3/2 clockwise:true];
    circleLayer.path = path.CGPath;
    
    //执行动画
    CABasicAnimation *checkAnimation = [CABasicAnimation animationWithKeyPath:@"strokeEnd"];
    checkAnimation.duration = circleDuriation;
    checkAnimation.fromValue = @(0.0f);
    checkAnimation.toValue = @(1.0f);
    checkAnimation.delegate = self;
    [checkAnimation setValue:@"checkAnimation" forKey:@"animationName"];
    [circleLayer addAnimation:checkAnimation forKey:nil];
}

2、对号动画

对号动画是利用了贝塞尔曲线的画线特性，设置了两段曲线拼接成了一个对号。如上图所示对号由线段AB和线段BC拼接完成，然后再利用核心动画和CAShapeLayer的strokeEnd属性实现对号动画。

-(void)checkAnimation{
    
    //外切圆的边长
    CGFloat a = _animationLayer.bounds.size.width;
    //设置三个点 A、B、C
    UIBezierPath *path = [UIBezierPath bezierPath];
    [path moveToPoint:CGPointMake(a*2.7/10,a*5.4/10)];
    [path addLineToPoint:CGPointMake(a*4.5/10,a*7/10)];
    [path addLineToPoint:CGPointMake(a*7.8/10,a*3.8/10)];
    
    //显示图层
    CAShapeLayer *checkLayer = [CAShapeLayer layer];
    checkLayer.path = path.CGPath;
    checkLayer.fillColor = [UIColor clearColor].CGColor;
    checkLayer.strokeColor = BlueColor.CGColor;
    checkLayer.lineWidth = lineWidth;
    checkLayer.lineCap = kCALineCapRound;
    checkLayer.lineJoin = kCALineJoinRound;
    [_animationLayer addSublayer:checkLayer];
    
    //执行动画
    CABasicAnimation *checkAnimation = [CABasicAnimation animationWithKeyPath:@"strokeEnd"];
    checkAnimation.duration = checkDuration;
    checkAnimation.fromValue = @(0.0f);
    checkAnimation.toValue = @(1.0f);
    checkAnimation.delegate = self;
    [checkAnimation setValue:@"checkAnimation" forKey:@"animationName"];
    [checkLayer addAnimation:checkAnimation forKey:nil];
}

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