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。
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)
}
}
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。
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。
