iphone - CoreAnimation CALayer 和 CATextLayer 组合

Question

我最近在玩CA。现在我有点卡住了。这就是我想要制作动画的东西:

现在我已经让圆形动画正常工作了。我将 CALayer 子类化来制作动画。我真的不知道从这里该去哪里。我必须在哪里添加 CATextLayer 的子图层？如何同时对两者进行动画处理，以便文本及其线条看起来粘在圆的末端？

如果您需要一些代码或其他任何东西，请告诉我。

我真的很高兴在这里得到一些帮助:-)

非常感谢!

Answer 1

我能够完成您在下面提出的要求。代码非常粗糙，只花了几分钟，可能错过了发布以及您有什么。您只需将 UILabel 替换为 CATextLayer(为简洁起见，使用 UILabel)。

    CAShapeLayer* circle = [[CAShapeLayer alloc] init];
    CGMutablePathRef path = CGPathCreateMutable();
    CGRect textRect = CGRectMake(self.bounds.size.width/4, (self.bounds.size.height-self.bounds.size.width/2)/2, self.bounds.size.width/2, self.bounds.size.width/2);
    float midX = CGRectGetMidX(textRect);
    float midY = CGRectGetMidY(textRect);
    CGAffineTransform t = CGAffineTransformConcat(
                            CGAffineTransformConcat(
                                CGAffineTransformMakeTranslation(-midX, -midY), 
                                CGAffineTransformMakeRotation(-1.57079633/0.99)), 
                            CGAffineTransformMakeTranslation(midX, midY));
    CGPathAddEllipseInRect(path, &t, textRect);
    circle.path = path;
    circle.frame = self.bounds;
    circle.fillColor = [UIColor clearColor].CGColor;
    circle.strokeColor = [UIColor blackColor].CGColor;
    circle.lineWidth = 60.0f;
    [self.layer addSublayer:circle];

    CABasicAnimation* animation = [CABasicAnimation animationWithKeyPath:@"strokeEnd"];
    animation.duration = 15.0f;
    animation.fromValue = [NSNumber numberWithFloat:0.0f];
    animation.toValue = [NSNumber numberWithFloat:1.0f];
    animation.timingFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionLinear];
    [circle addAnimation:animation forKey:@"strokeEnd"];

    [circle release];

    UILabel* label = [[UILabel alloc] init];
    label.text = @"Test Text";
    label.font = [UIFont systemFontOfSize:20.0f];
    label.center = CGPathGetCurrentPoint(path);
    label.transform = CGAffineTransformMakeRotation(1.57079633);
    [label sizeToFit];
    [self.layer addSublayer:label.layer];

    CAKeyframeAnimation* textAnimation = [CAKeyframeAnimation animationWithKeyPath:@"position"];
    textAnimation.duration = 15.0f;
    textAnimation.path = path;
    textAnimation.rotationMode = kCAAnimationRotateAuto;
    textAnimation.calculationMode = kCAAnimationCubicPaced;
    textAnimation.removedOnCompletion = NO;
    [label.layer addAnimation:textAnimation forKey:@"position"];