iOS - 尝试旋转文字标签，标签消失 [英] iOS - trying to rotate a text label and the label disappears

问题描述

我想在我的视图上旋转一个标签90度。我试过以下两种方法来做，标签只是从屏幕上消失。我三次检查属性是否正确附加。任何想法？

I'm trying to rotate a label on my view 90 degrees. I've tried the two following ways to do it and the label just disappears from the screen. I triple checked that the properties are properly attached. Any thoughts?

尝试一个：

// rotating labels 90 degrees
self.labelCloseScroll.transform = CGAffineTransformMakeRotation (3.14/2);

尝试两个：

CGAffineTransform rotate = CGAffineTransformMakeRotation(3.14/2);
rotate = CGAffineTransformScale(rotate, 1, 1);
[self.labelCloseScroll setTransform:rotate];

推荐答案

我不是100％但为什么你不使用 M_PI_2 。这只是简单的想法，你假设价值Pi 为 3.14 ，但确切的值是 3.14159 ...

I am not 100% sure if it works or not but why are you not using M_PI_2. It's just simple thought that you are assuming Value of Pi to be 3.14 but the exact value is 3.14159...

我这样做，效果很好：

UILabel *lbl = [[UILabel alloc] initWithFrame:CGRectMake(10, 10, 50, 70)];
lbl.text = @"New";
lbl.backgroundColor = [UIColor clearColor];
lbl.textColor = [UIColor whiteColor];
lbl.highlightedTextColor = [UIColor blackColor];
lbl.font = [UIFont systemFontOfSize:12];
lbl.transform = CGAffineTransformMakeRotation(M_PI_2);
[self.view addSubview:lbl];

您也可以检查这些问题的答案：

You can also check Answers from these Questions :

如何呈现旋转的UIlabel

旋转UILabel在其中心

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