向UIView添加渐变的现代技术 [英] Modern technique of adding gradient to UIView

问题描述

我知道几种向UIView添加背景渐变的方法。我想知道什么是最有效和可扩展的方式，为什么？以下是我使用的技术：

I know of several ways of adding background gradients to UIView. I was wondering what is the most efficient and scalable way of doing so, and why? Here are the techniques I've used:

• 创建UIView的子视图并覆盖drawRect，我在当前绘制渐变上下文。

• Create subview of UIView and overwrite the drawRect, where I draw the gradient in current context.

a。当使用上面的渐变创建它时，我想要装饰视图的边界，并将此背景渐变作为第一个子视图插入，即 - insertSubview：atIndex：

a. When using the above gradient create it with the bounds of view I want to decorate and insert this background gradient as first subview, i.e. – insertSubview:atIndex:

b。从上面得到背景渐变视图后，我在图像上下文中渲染它并将其用作背景图像，即

b. After I get the background gradient view from above, I render it in image context and use it as background image, i.e.

UIGraphicsBeginImageContext(gradView.bounds.size);
[gradView.layer renderInContext:UIGraphicsGetCurrentContext()];
UIImage *gradientImg = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
UIColor *background = [UIColor colorWithPatternImage:gradientImg];
self.view.backgroundColor = background;

创建可伸缩的PNG并使用它来装饰视图背景。技术与你装饰UIButton的方式非常相似。

Create stretchable PNG and use that to decorate view background. Technique is very similar to the way you decorate UIButton.

-(UIColor *)backgroundColor:(CGRect)frame
{
    UIImage *bg = [UIImage imageNamed:@"background_23x36"];
    bg = [bg resizableImageWithCapInsets:UIEdgeInsetsMake(0.0, 11.0, 0.0, 11.0)];
    UIGraphicsBeginImageContextWithOptions(frame.size, YES, [[UIScreen mainScreen] scale]);
    [bg drawInRect:frame];
    UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    return [UIColor colorWithPatternImage:image];
}

创建UIView的子视图，但不要覆盖drawRect，而是使用CAGradientLayer。与 http：// nscookbook相似。 com / 2013/04 / recipe-20-using-cagradient-layer-in-a-custom-view /

那么添加渐变作为背景的最有效和可扩展的方法是什么？

So what is most efficient and scalable way to add gradient as a background?

推荐答案

正如上面提到的Fogmeister所做，请在 drawRect：方法中进行您的 UIView 子类。

As Fogmeister suggested above, do it in the drawRect: method of your UIView subclass.

- (void)drawRect:(CGRect)rect
{
    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
    CGContextRef context = UIGraphicsGetCurrentContext();

    NSArray *gradientColors = [NSArray arrayWithObjects:(id) [UIColor redColor].CGColor, [UIColor yellowColor].CGColor, nil];

    CGFloat gradientLocations[] = {0, 0.50, 1};
    CGGradientRef gradient = CGGradientCreateWithColors(colorSpace, (__bridge CFArrayRef) gradientColors, gradientLocations);

    CGPoint startPoint = CGPointMake(CGRectGetMidX(rect), CGRectGetMinY(rect));
    CGPoint endPoint = CGPointMake(CGRectGetMidX(rect), CGRectGetMaxY(rect));

    CGContextDrawLinearGradient(context, gradient, startPoint, endPoint, 0);
    CGGradientRelease(gradient);
    CGColorSpaceRelease(colorSpace);
}

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