ios UIButton一直旋轉動畫

-(void)viewDidAppear:(BOOL)animated{
​ UIButton * buyBtn = [[UIButton alloc]initWithFrame:CGRectMake(10, 0, 50, 50)];
[buyBtn setImage:[UIImage imageNamed:@"AppIcon40x40"] forState:UIControlStateNormal];
[segmentView2 addSubview:buyBtn];
buyBtn=[self rotate360DegreeWithImageView:buyBtn];
}

• (UIButton *)rotate360DegreeWithImageView:(UIButton *)imageView{

  CABasicAnimation *animation = [ CABasicAnimation animationWithKeyPath: @"transform" ];

  animation.fromValue = [NSValue valueWithCATransform3D:CATransform3DIdentity];

  //圍繞Z軸旋轉，垂直與螢幕

  animation.toValue = [ NSValue valueWithCATransform3D:CATransform3DMakeRotation(M_PI/2.0, 0.0, 0.0, 1.0) ];

  animation.duration = 3;

  //旋轉效果累計，先轉180度，接著再旋轉180度，從而實現360旋轉

  animation.cumulative = YES;

  animation.repeatCount = MAXFLOAT;

  /*下面可以不需要
  CGRect imageRrect = CGRectMake(0, 0,imageView.imageView.frame.size.width, imageView.imageView.frame.size.height);
  UIGraphicsBeginImageContext(imageRrect.size);
  //在圖片邊緣新增一個畫素的透明區域，去圖片鋸齒
  [imageView.currentImage drawInRect:CGRectMake(1,1,imageView.imageView.frame.size.width-2,imageView.imageView.frame.size.height-2)];
  [imageView setImage: UIGraphicsGetImageFromCurrentImageContext() forState:UIControlStateNormal];
  UIGraphicsEndImageContext();
  */
  [imageView.layer addAnimation:animation forKey:nil];

  return imageView;
  }