CAShapeLayer 动画 iOS7 的问题

Question

我一直在努力解决 iOS7 上的动画效果（8、9 效果很好），它涉及将圆角矩形收缩成圆形。为了得到这样的效果。

但我在 iOS7 上尝试收缩圆圈时出现了一些失真。

我的视图控制器非常简单

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.

    CAShapeLayer *layer = [CAShapeLayer layer];
    layer.fillColor = [UIColor blackColor].CGColor;
    layer.frame = CGRectMake(100, 100, 100, 100);
    layer.path = [UIBezierPath bezierPathWithRoundedRect:CGRectMake(0, 0, 100, 50) cornerRadius:25].CGPath;
    self.myLayer = layer;
    [self.view.layer addSublayer:layer];

}


- (void)viewDidAppear:(BOOL)animated {
    [super viewDidAppear:animated];

    CAKeyframeAnimation *animation = [CAKeyframeAnimation animationWithKeyPath:@"path"];
    animation.values = @[
                         (id)[UIBezierPath bezierPathWithRoundedRect:CGRectMake(0, 0, 100, 50) cornerRadius:25].CGPath,
                         (id)[UIBezierPath bezierPathWithRoundedRect:CGRectMake(5, 0, 90, 50) cornerRadius:25].CGPath,
                         (id)[UIBezierPath bezierPathWithRoundedRect:CGRectMake(10, 0, 80, 50) cornerRadius:25].CGPath,
                         (id)[UIBezierPath bezierPathWithRoundedRect:CGRectMake(15, 0, 70, 50) cornerRadius:25].CGPath,
                         (id)[UIBezierPath bezierPathWithRoundedRect:CGRectMake(20, 0, 60, 50) cornerRadius:25].CGPath,
                         (id)[UIBezierPath bezierPathWithRoundedRect:CGRectMake(25, 0, 50, 50) cornerRadius:25].CGPath,
                         ];

    animation.keyTimes = @[@(0),
                           @(0.18),
                           @(0.36),
                           @(0.54),
                           @(0.72),
                           @(1),
                           ];

    animation.duration = 10;
    animation.fillMode = kCAFillModeForwards;
    [self.myLayer addAnimation:animation forKey:nil];
    self.myLayer.path = [UIBezierPath bezierPathWithRoundedRect:CGRectMake(25, 0, 50, 50) cornerRadius:25].CGPath;
}

Answer 1

这似乎是 iOS 7 的一个错误。查看此链接：

http://www.paintcodeapp.com/blogpost/code-for-ios-7-rounded-rectangles

帖子底部有一个类别方法可以解决此问题。 我用你的代码测试了它，它似乎工作！我不得不做一个小改动，那就是替换

CGFloat limitedRadius = MIN(radius, limit);

与

CGFloat limitedRadius = radius;

这使得拐角半径变得足够大以创建一个圆。可能值得研究一下为什么拐角半径一开始就受到限制，但我会把它留给你 :)