iOS动画解析之支付宝支付打钩动画的实现方法

{
 //刷新工具
 CADisplayLink *_link;
 //显示圆环
 CAShapeLayer *_animationLayer;
 //起始角度
 CGFloat _startAngle;
 //结束角度
 CGFloat _endAngle;
 //当前动画进度
 CGFloat _progress;
}

 _link = [CADisplayLink displayLinkWithTarget:self selector:@selector(displayLinkAction)];
 [_link addToRunLoop:[NSRunLoop mainRunLoop] forMode:NSDefaultRunLoopMode];
 _link.paused = true;

-(CGFloat)speed{
 if (_endAngle > M_PI) {
  return 0.1/60.0f;
 }
 return 0.8/60.0f;
}

-(void)displayLinkAction{
 _progress += [self speed];
 if (_progress >= 1) {
  _progress = 0;
 }
 [self updateAnimationLayer];
}

-(void)updateAnimationLayer{

 _startAngle = -M_PI_2;
 _endAngle = -M_PI_2 +_progress * M_PI * 2;

 if (_endAngle > M_PI) {
  CGFloat progress1 = 1 - (1 - _progress)/0.25;
  _startAngle = -M_PI_2 + progress1 * M_PI * 2;
 }
 CGFloat radius = _animationLayer.bounds.size.width/2.0f - lineWidth/2.0f;
 CGFloat centerX = _animationLayer.bounds.size.width/2.0f;
 CGFloat centerY = _animationLayer.bounds.size.height/2.0f;
 UIBezierPath *path = [UIBezierPath bezierPathWithArcCenter:CGPointMake(centerX, centerY) radius:radius startAngle:_startAngle endAngle:_endAngle clockwise:true];
 path.lineCapStyle = kCGLineCapRound;

 _animationLayer.path = path.CGPath;
}

-(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];
}

-(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];
}