xcode Xcode顺时针旋转uibutton
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Xcode rotate uibutton clockwise
提问by CristiC
I want to rotate an UIButton at 180 degrees clockwise. But it always rotate counterclockwise.
我想将 UIButton 顺时针旋转 180 度。但它总是逆时针旋转。
This is how I tried:
这是我尝试的方式：
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:
还有这个：
myButton.transform = CGAffineTransformRotate( myButton.transform, - M_PI);
What am I doing wrong?
我究竟做错了什么？
回答by Lecrte
I've had a similar experience, and my best guess is the following:
我有过类似的经历，我最好的猜测如下：
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.
旋转变换转化为净结果，即绝对旋转。由于旋转 -PI 和 +PI 会产生相同的净效果（均为 180 度），因此动画最终总是选择默认方向；这在 iOS 上似乎是逆时针的。
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.
正如@kishorebjv 提到的，通过将其设置为比 -M_PI 稍负的值，最短的旋转路径是通过正方向（将动画切换为顺时针方向）。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，但它们导致不同的方向。
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.
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，因此最短的旋转是负 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
回答by kishorebjv
I'm surprised..I don't know why its happening like that.
我很惊讶..我不知道为什么会这样。
Instead of -M_PI give -3.141593.
而不是 -M_PI 给 -3.141593。
It 'll rotate clockwise..
它会顺时针旋转..
as of now its a quick fix.but probably not a exact answer for your question
到目前为止，它是一个快速修复。但可能不是您问题的确切答案
