Xcode顺时针旋转uibutton

发布于 2024-10-18 02:13:13 字数 513 浏览 1 评论 0原文

我想将 UIButton 顺时针旋转 180 度。但它总是逆时针旋转。

这就是我尝试的方法：

CGContextRef context = UIGraphicsGetCurrentContext();
[UIView beginAnimations:nil context:context];
[UIView setAnimationCurve:UIViewAnimationCurveEaseInOut];
[UIView setAnimationDuration:0.3];

myButton.transform = CGAffineTransformRotate( myButton.transform, M_PI);

[UIView commitAnimations];

也是这样：

myButton.transform = CGAffineTransformRotate( myButton.transform, - M_PI);

我做错了什么？

原文

I want to rotate an UIButton at 180 degrees clockwise. But it always rotate counterclockwise.

This is how I tried:

CGContextRef context = UIGraphicsGetCurrentContext();
[UIView beginAnimations:nil context:context];
[UIView setAnimationCurve:UIViewAnimationCurveEaseInOut];
[UIView setAnimationDuration:0.3];

myButton.transform = CGAffineTransformRotate( myButton.transform, M_PI);

[UIView commitAnimations];

also this:

myButton.transform = CGAffineTransformRotate( myButton.transform, - M_PI);

What am I doing wrong?

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堇色安年 2024-10-25 02:13:13

我有过类似的经历，我最好的猜测如下：

旋转变换转换为最终结果，意味着绝对旋转。由于旋转 -PI 和 +PI 会产生相同的最终效果（均为 180 度），因此动画最终始终选择默认方向；在 iOS 上似乎是逆时针方向。

通过将其设置为比 -M_PI 稍负的值，如 @kishorebjv 提到的，最短旋转路径是通过正方向（将动画切换为顺时针）。您可以使用 M_PI+0.01 或 M_PI-0.01 来查看此效果。两者都是正数，但它们的结果不同。

更详细的解释：
值：M_PI+0.01
方向: 逆时针
推理：这转化为 ~180.6 的旋转，
因此，最短旋转为负 179.4 度。

Value: M_PI-0.01
Direction: Clockwise
Reasoning: This is this translates to a rotation of ~179.4, 
which the shortest rotation is thus a positive 179.4 degrees.

And going back to the value given by kishorebjv
Value: -3.141593
Direction: Clockwise
Reasoning: The value is slightly past -180 degrees, recalling PI is 3.1415926
....so the shortest rotation is a positive 179 degrees

I've had a similar experience, and my best guess is the following:

The rotation transform translates to a net result, meaning an absolute rotation. Since rotating -PI and +PI results in the same net effect (both 180 degrees), the animation ends up always choosing the default direction; which seems to be counterclockwise on iOS.

By setting it to a value slightly more negative than -M_PI, as @kishorebjv mentioned, the shortest rotation path is through the positive direction (switching the animation to clockwise). You can see this effect by using M_PI+0.01 or M_PI-0.01. Both are positive numbers, but they result in different directions.

More verbose explanation:
Value: M_PI+0.01
Direction: Counterclockwise
Reasoning: This is this translates to a rotation of ~180.6,
which the shortest rotation is thus a negative 179.4 degrees.

Value: M_PI-0.01
Direction: Clockwise
Reasoning: This is this translates to a rotation of ~179.4, 
which the shortest rotation is thus a positive 179.4 degrees.

And going back to the value given by kishorebjv
Value: -3.141593
Direction: Clockwise
Reasoning: The value is slightly past -180 degrees, recalling PI is 3.1415926
....so the shortest rotation is a positive 179 degrees

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