iphone - 顺时针旋转 UIView 大于 180 度的角度

Question

我正在为一个时钟臂设置动画，使其从指向 12 点钟指向当前时间。如果说，11 点钟，我想让 ARM 顺时针旋转到 11 点钟的位置。但当然如果我使用:

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

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

逆时针旋转。我试过:

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进行的，但它是断断续续的——动画似乎仍然在为第一个动画执行 UIViewAnimationEaseInOut。我做错了什么，或者是否有其他方法可以实现我想要的？

Answer 1

您可以使用 CATransaction 的完成 block 来设置动画完成时 View 的旋转属性。以下函数在我的测试用例中有效:

- (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];
}

你喜欢用它

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