我试图旋转一个UIImageView 360度，并在网上看了几个教程。我不能让它们都工作，UIView要么停止，要么跳转到一个新位置。
我怎样才能做到这一点呢?
我最近尝试的是:
[UIView animateWithDuration:1.0
delay:0.0
options:0
animations:^{
imageToMove.transform = CGAffineTransformMakeRotation(M_PI);
}
completion:^(BOOL finished){
NSLog(@"Done!");
}];
但如果我使用2*pi，它根本不会移动(因为它是相同的位置)。如果我尝试只做(180度)，它可以工作，但如果我再次调用这个方法，它会向后旋转。
编辑:
[UIView animateWithDuration:1.0
delay:0.0
options:0
animations:^{
[UIView setAnimationRepeatCount:HUGE_VALF];
[UIView setAnimationBeginsFromCurrentState:YES];
imageToMove.transform = CGAffineTransformMakeRotation(M_PI);
}
completion:^(BOOL finished){
NSLog(@"Done!");
}];
也不管用。它会转到180度，暂停一秒钟，然后在重新开始之前重置回0度。
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。
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")
}
}
