如何为iOS导航栏创建水平渐变背景？ [英] How can I create a horizontal gradient background for my iOS nav bar?

问题描述

我知道如何设置导航栏背景颜色（使用barTintColor），但现在我正在开发一个需要水平渐变（不是典型的垂直渐变）的iOS应用。

I know how to set a navigation bar background color (with barTintColor), but now I am working on an iOS app that calls for a horizontal gradient (not the typical vertical gradient).

如何创建具有水平渐变背景的导航栏？

How can I create a navigation bar with a horizontal gradient background?

推荐答案

如果要以编程方式设置给定UINavigationBar的梯度我有一个解决方案。

If you want to programmatically set the gradient of a given UINavigationBar I have a solution for you.

首先使用您想要的颜色和位置设置 CAGradientLayer 。

First setup a CAGradientLayer with your desired colors and locations.

CAGradientLayer *gradientLayer = [CAGradientLayer layer];
gradientLayer.frame = navigationBar.bounds;
gradientLayer.colors = @[ (__bridge id)[UIColor greenColor].CGColor,
                          (__bridge id)[UIColor blueColor].CGColor ];
gradientLayer.startPoint = CGPointMake(0.0, 0.5);
gradientLayer.endPoint = CGPointMake(1.0, 0.5);

然后抓住该图层的UImage。

Then grab the UImage for that layer.

UIGraphicsBeginImageContext(gradientLayer.bounds.size);
[gradientLayer renderInContext:UIGraphicsGetCurrentContext()];
UIImage *gradientImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();

将 gradientImage 设置为您的backgroundImage UINavigationBar 。

Set the gradientImage as the backgroundImage for your UINavigationBar.

[navigationBar setBackgroundImage:gradientImage forBarMetrics:UIBarMetricsDefault];

Swift解决方案：

Swift Solution:

[![// Setup the gradient
let gradientLayer = CAGradientLayer()
gradientLayer.frame = navigationBar.bounds
gradientLayer.colors = [UIColor.green.cgColor, UIColor.blue.cgColor]
gradientLayer.startPoint = CGPoint(x: 0.0, y: 0.5)
gradientLayer.endPoint = CGPoint(x: 1.0, y: 0.5)

// Render the gradient to UIImage
UIGraphicsBeginImageContext(gradientLayer.bounds.size)
gradientLayer.render(in: UIGraphicsGetCurrentContext()!)
let image = UIGraphicsGetImageFromCurrentImageContext()
UIGraphicsEndImageContext()

 Set the UIImage as background property
navigationBar.setBackgroundImage(image, for: UIBarMetrics.default)

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