在UIView上使用CAGradientLayer绘制渐变不起作用 [英] Drawing gradient using CAGradientLayer on UIView not working

问题描述

我正在尝试使用View Controller的背景视图绘制渐变，但是由于某种原因，我无法使其正常工作.

I'm trying to draw a gradient on the background view of a View Controller with but for some reason I couldn't get it to work.

这是我的方法，从viewDidLoad调用:

Here is my method, which is called from viewDidLoad:

- (void)drawGradient
{
  CAGradientLayer *gradient = [CAGradientLayer layer];
  gradient.frame = self.view.bounds;

  gradient.colors = @[[UIColor greenColor], [UIColor redColor]];
  gradient.locations = @[@0.0, @1.0];

  [self.view.layer insertSublayer:gradient atIndex:0];
}

...但是什么也没有发生，并且没有出现渐变. 我在做什么错了?

...but nothing happens, and the gradient doesn't appear. What am I doing wrong?

推荐答案

感谢Larme的评论，我发现了我的错误.

Thanks to Larme's comment, I figured out my mistake.

代替

gradient.colors = @[[UIColor greenColor], [UIColor redColor]];

这是右边

gradient.colors = @[(id)[UIColor greenColor].CGColor, (id)[UIColor redColor].CGColor];

因为gradient.colors期望NSArray为CGColorRef.为了创建NSArray，还需要(id)强制转换.

Because gradient.colors expects a NSArray of CGColorRef. The (id) cast is also needed in order to create the NSArray.

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