CAShapeLayer *shapeLayer = [CAShapeLayer layer];
shapeLayer.frame = _demoView.bounds;
shapeLayer.strokeEnd = 0.7f;
shapeLayer.strokeStart = 0.1f;
UIBezierPath *path = [UIBezierPath bezierPathWithOvalInRect:_demoView.bounds];
shapeLayer.path = path.CGPath;
shapeLayer.fillColor = [UIColor clearColor].CGColor;
shapeLayer.lineWidth = 2.0f;
shapeLayer.strokeColor = [UIColor redColor].CGColor;
[_demoView.layer addSublayer:shapeLayer];
CAShapeLayer *shapeLayer = [CAShapeLayer layer];
shapeLayer.frame = _demoView.bounds;
UIBezierPath *path = [UIBezierPath bezierPathWithOvalInRect:_demoView.bounds];
shapeLayer.path = path.CGPath;
shapeLayer.fillColor = [UIColor clearColor].CGColor;
shapeLayer.lineWidth = 2.0f;
shapeLayer.strokeColor = [UIColor redColor].CGColor;
[_demoView.layer addSublayer:shapeLayer];
//动画添加
CABasicAnimation *pathAnima = [CABasicAnimation animationWithKeyPath:@"strokeEnd"];
pathAnima.duration = 3.0f;
pathAnima.timingFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionEaseInEaseOut];
pathAnima.fromValue = [NSNumber numberWithFloat:0.0f];
pathAnima.toValue = [NSNumber numberWithFloat:1.0f];
pathAnima.fillMode = kCAFillModeForwards;
pathAnima.removedOnCompletion = NO;
[shapeLayer addAnimation:pathAnima forKey:@"strokeEndAnimation"];
