Kudos to Richard J. Ross III for the idea, but I found that his code wasn't quite what I needed. The default for options, I believe, is to give you UIViewAnimationOptionCurveEaseInOut, which doesn't look right in a continuous animation. Also, I added a check so that I could stop my animation at an even quarter turn if I needed (not infinite, but of indefinite duration), and made the acceleration ramp up during the first 90 degrees, and decelerate during the last 90 degrees (after a stop has been requested):

// an ivar for your class:
BOOL animating;

- (void)spinWithOptions:(UIViewAnimationOptions)options {
   // this spin completes 360 degrees every 2 seconds
   [UIView animateWithDuration:0.5
                         delay:0
                       options:options
                    animations:^{
                       self.imageToMove.transform = CGAffineTransformRotate(imageToMove.transform, M_PI / 2);
                    }
                    completion:^(BOOL finished) {
                       if (finished) {
                          if (animating) {
                             // if flag still set, keep spinning with constant speed
                             [self spinWithOptions: UIViewAnimationOptionCurveLinear];
                          } else if (options != UIViewAnimationOptionCurveEaseOut) {
                             // one last spin, with deceleration
                             [self spinWithOptions: UIViewAnimationOptionCurveEaseOut];
                          }
                       }
                    }];
}

- (void)startSpin {
   if (!animating) {
      animating = YES;
      [self spinWithOptions: UIViewAnimationOptionCurveEaseIn];
   }
}

- (void)stopSpin {
    // set the flag to stop spinning after one last 90 degree increment
    animating = NO;
}

更新

我添加了处理请求重新开始旋转(startSpin)的能力，而之前的旋转正在结束(完成)。Github上的示例项目。

Nate上面的答案是理想的停止和开始动画，并提供了一个更好的控制。我很好奇为什么你的没用，而他的有用。我想在这里分享我的发现和一个更简单的代码版本，它可以使UIView连续动画而不停顿。

这是我用的代码，

- (void)rotateImageView
{
    [UIView animateWithDuration:1 delay:0 options:UIViewAnimationOptionCurveLinear animations:^{
        [self.imageView setTransform:CGAffineTransformRotate(self.imageView.transform, M_PI_2)];
    }completion:^(BOOL finished){
        if (finished) {
            [self rotateImageView];
        }
    }];
}

我使用“CGAffineTransformRotate”而不是“CGAffineTransformMakeRotation”，因为前者返回的结果是随着动画的进行而保存的。这将防止在动画期间视图的跳跃或重置。

另一件事是不要使用'UIViewAnimationOptionRepeat'因为在动画的结尾，在它开始重复之前，它会重置变换，使视图跳回它的原始位置。不是重复，而是递归，这样转换就永远不会重置为原始值，因为动画块实际上永远不会结束。

最后一件事是，你必须以90度(M_PI / 2)的步伐转换视图，而不是360度或180度(2*M_PI或M_PI)。因为变换是正弦和余弦值的矩阵乘法。

t' =  [ cos(angle) sin(angle) -sin(angle) cos(angle) 0 0 ] * t

所以，假设你使用180度变换，cos(180)产生-1，使得视图每次都在相反的方向变换(如果你把变换的弧度值改为M_PI, Note-Nate的答案也会有这个问题)。360度转换只是要求视图保持在原来的位置，因此你根本看不到任何旋转。

这是我的快速解决方案作为一个UIView扩展。它可以被认为是任何UIImageView上UIActivityIndicator行为的模拟。

import UIKit

extension UIView
{

    /**
    Starts rotating the view around Z axis.

    @param duration Duration of one full 360 degrees rotation. One second is default.
    @param repeatCount How many times the spin should be done. If not provided, the view will spin forever.
    @param clockwise Direction of the rotation. Default is clockwise (true).
     */
    func startZRotation(duration duration: CFTimeInterval = 1, repeatCount: Float = Float.infinity, clockwise: Bool = true)
    {
        if self.layer.animationForKey("transform.rotation.z") != nil {
            return
        }
        let animation = CABasicAnimation(keyPath: "transform.rotation.z")
        let direction = clockwise ? 1.0 : -1.0
        animation.toValue = NSNumber(double: M_PI * 2 * direction)
        animation.duration = duration
        animation.cumulative = true
        animation.repeatCount = repeatCount
        self.layer.addAnimation(animation, forKey:"transform.rotation.z")
    }


    /// Stop rotating the view around Z axis.
    func stopZRotation()
    {
        self.layer.removeAnimationForKey("transform.rotation.z")
    }

}

如果你想要做的只是无休止地旋转图像，这很好，而且非常简单:

NSTimeInterval duration = 10.0f;
CGFloat angle = M_PI / 2.0f;
CGAffineTransform rotateTransform = CGAffineTransformRotate(imageView.transform, angle);

[UIView animateWithDuration:duration delay:0 options:UIViewAnimationOptionRepeat| UIViewAnimationOptionCurveLinear animations:^{
    imageView.transform = rotateTransform;
} completion:nil];

根据我的经验，这是完美的，但要确保你的图像能够在没有任何偏移的情况下围绕其中心旋转，否则图像动画将“跳跃”一旦它到达PI。

要改变旋转的方向，改变角度的符号(angle *= -1)。

@AlexPretzlav的更新评论让我重新审视了这个问题，我意识到当我写这篇文章时，我旋转的图像是沿着垂直和水平轴镜像的，这意味着图像确实只旋转了90度，然后重置，尽管它看起来像在继续旋转。

所以，如果你的图像像我的一样，这将工作得很好，然而，如果图像不是对称的，你会注意到90度后“snap”回到原来的方向。

要旋转非对称图像，最好使用公认的答案。

这些不太优雅的解决方案之一，如下所示，将真正旋转图像，但当动画重新启动时可能会有明显的口吃:

- (void)spin
{
    NSTimeInterval duration = 0.5f;
    CGFloat angle = M_PI_2;
    CGAffineTransform rotateTransform = CGAffineTransformRotate(self.imageView.transform, angle);

    [UIView animateWithDuration:duration delay:0 options:UIViewAnimationOptionCurveLinear animations:^{
        self.imageView.transform = rotateTransform;
    } completion:^(BOOL finished) {
        [self spin];
    }];
}

你也可以像@richard-j-ross-iii建议的那样只用块来做，但你会得到一个保留循环警告，因为块正在捕获自己:

__block void(^spin)() = ^{
    NSTimeInterval duration = 0.5f;
    CGFloat angle = M_PI_2;
    CGAffineTransform rotateTransform = CGAffineTransformRotate(self.imageView.transform, angle);

    [UIView animateWithDuration:duration delay:0 options:UIViewAnimationOptionCurveLinear animations:^{
        self.imageView.transform = rotateTransform;
    } completion:^(BOOL finished) {
        spin();
    }];
};
spin();

我的贡献与一个快速扩展从检查解决方案:

斯威夫特4.0

extension UIView{
    func rotate() {
        let rotation : CABasicAnimation = CABasicAnimation(keyPath: "transform.rotation.z")
        rotation.toValue = NSNumber(value: Double.pi * 2)
        rotation.duration = 1
        rotation.isCumulative = true
        rotation.repeatCount = Float.greatestFiniteMagnitude
        self.layer.add(rotation, forKey: "rotationAnimation")
    }
}

弃用:

extension UIView{
    func rotate() {
        let rotation : CABasicAnimation = CABasicAnimation(keyPath: "transform.rotation.z")
        rotation.toValue = NSNumber(double: M_PI * 2)
        rotation.duration = 1
        rotation.cumulative = true
        rotation.repeatCount = FLT_MAX
        self.layer.addAnimation(rotation, forKey: "rotationAnimation")
    }
}

在Swift中，你可以使用以下代码进行无限旋转:

斯威夫特4

extension UIView {
    private static let kRotationAnimationKey = "rotationanimationkey"

    func rotate(duration: Double = 1) {
        if layer.animation(forKey: UIView.kRotationAnimationKey) == nil {
            let rotationAnimation = CABasicAnimation(keyPath: "transform.rotation")

            rotationAnimation.fromValue = 0.0
            rotationAnimation.toValue = Float.pi * 2.0
            rotationAnimation.duration = duration
            rotationAnimation.repeatCount = Float.infinity

            layer.add(rotationAnimation, forKey: UIView.kRotationAnimationKey)
        }
    }

    func stopRotating() {
        if layer.animation(forKey: UIView.kRotationAnimationKey) != nil {
            layer.removeAnimation(forKey: UIView.kRotationAnimationKey)
        }
    }
}

斯威夫特3

let kRotationAnimationKey = "com.myapplication.rotationanimationkey" // Any key

func rotateView(view: UIView, duration: Double = 1) {
    if view.layer.animationForKey(kRotationAnimationKey) == nil {
        let rotationAnimation = CABasicAnimation(keyPath: "transform.rotation")

        rotationAnimation.fromValue = 0.0
        rotationAnimation.toValue = Float(M_PI * 2.0)
        rotationAnimation.duration = duration
        rotationAnimation.repeatCount = Float.infinity

        view.layer.addAnimation(rotationAnimation, forKey: kRotationAnimationKey)
    }
}

停下来就像:

func stopRotatingView(view: UIView) {
    if view.layer.animationForKey(kRotationAnimationKey) != nil {
        view.layer.removeAnimationForKey(kRotationAnimationKey)
    }
}