顺时针旋转UIView大于180度的角度 [英] Rotate a UIView clockwise for an angle greater than 180 degrees

问题描述

我将钟表臂指向12点钟到当前时间。如果是，11点，我想让手臂顺时针旋转到11点位置。不过，当然，如果我使用：

I'm animating a clock arm from pointing towards 12 o'clock to the current time. If it is say, 11 o'clock, I want the arm to rotate clockwise to the 11 o'clock position. But of course if I use:

 CGAffineTransform rotation = CGAffineTransformMakeRotation(2*M_PI*11/12);

 [UIView animateWithDuration:3.0
                  animations:^{
                         clockArm.transform = rotation;
                     }];

旋转逆时针旋转。我试过了：

the rotation goes counterclockwise. I tried:

CGFloat angle = 2*M_PI*11/12;
CGAffineTransform firstRotation = CGAffineTransformMakeRotation(M_PI-0.001);
CGFloat firstRotationTime = 3.0*(M_PI/angle);
CGAffineTransform secondRotation = CGAffineTransformMakeRotation(angle);
CGFloat secondRotationTime = 3.0 - firstRotationTime;

[UIView animateWithDuration:firstRotationTime
                      delay:0.0
                    options:UIViewAnimationCurveLinear
                 animations:^{
                         self.clockArm1.transform = firstRotation;
                     }
                 completion:^(BOOL finished) {
                     [UIView animateWithDuration:secondRotationTime
                                           delay:0.0
                                         options:UIViewAnimationCurveLinear
                                      animations:^{
                                          self.clockArm1.transform = secondRotation;
                                      }
                                      completion:^(BOOL finished){
                                      }];
                 }];

动画确实是顺时针方向，但它很不稳定 - 动画似乎仍然在做一个UIViewAnimationEaseInOut第一个动画。我做错了什么，或者有其他方法可以实现我想要的目标吗？

The animation does go clockwise, but it is choppy - the animation still seems to be doing a UIViewAnimationEaseInOut for the first animation. What am I doing wrong, or is there another way to accomplish what I want?

推荐答案

你可以使用<的完成块code> CATransaction 在动画结束时设置视图的rotation属性。以下函数在我的测试用例中起作用：

You can use the completion block of CATransaction to set the rotation property of the view when the animation has finished. The following function worked in my test case:

- (void) rotateViewAnimated:(UIView*)view
               withDuration:(CFTimeInterval)duration
                    byAngle:(CGFloat)angle
{
    [CATransaction begin];
    CABasicAnimation *rotationAnimation;
    rotationAnimation = [CABasicAnimation animationWithKeyPath:@"transform.rotation.z"];
    rotationAnimation.byValue = [NSNumber numberWithFloat:angle];
    rotationAnimation.duration = duration;
    rotationAnimation.removedOnCompletion = YES;

    [CATransaction setCompletionBlock:^{
        view.transform = CGAffineTransformRotate(view.transform, angle);
    }];

    [view.layer addAnimation:rotationAnimation forKey:@"rotationAnimation"];
    [CATransaction commit];
}

您可以像

[self rotateViewAnimated:self.clockArm1 withDuration:3.0 byAngle:2*M_PI*11./12.];

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