iOS沿一个贝塞尔曲线对图层做动画

- (void)viewDidLoad {
    [super viewDidLoad];
    
    CGFloat bezierPathH = self.view.bounds.size.height - 200;
    UIBezierPath *bezierPath = [[UIBezierPath alloc] init];
    [bezierPath moveToPoint:CGPointMake(self.view.bounds.size.width / 2, 100)];
    
    // 三次贝塞尔曲线
    [bezierPath addCurveToPoint:CGPointMake(self.view.bounds.size.width / 2, self.view.bounds.size.height - 100) controlPoint1:CGPointMake(self.view.bounds.size.width / 4 * 3, bezierPathH / 4 + 100) controlPoint2:CGPointMake(self.view.bounds.size.width / 4, bezierPathH / 4 * 3 + 100)];
    CAShapeLayer *pathLayer = [CAShapeLayer layer];
    pathLayer.path = bezierPath.CGPath;
    pathLayer.fillColor = [UIColor clearColor].CGColor;
    pathLayer.strokeColor = [UIColor redColor].CGColor;
    pathLayer.lineWidth = 3.0f;
    [self.view.layer addSublayer:pathLayer];
    
    CALayer *shipLayer = [CALayer layer];
    shipLayer.frame = CGRectMake(0, 0, 64, 64);
    shipLayer.position = CGPointMake(self.view.bounds.size.width / 2, 100);
    shipLayer.contents = (__bridge id)[UIImage imageNamed:@"ship"].CGImage;
    [self.view.layer addSublayer:shipLayer];
    
    CAKeyframeAnimation *animation = [CAKeyframeAnimation animation];
    animation.keyPath = @"position";
    animation.path = bezierPath.CGPath;
    animation.duration = 4.0;
    animation.rotationMode = kCAAnimationRotateAuto;
    [shipLayer addAnimation:animation forKey:nil];   
}