如何为iOS导航栏创建水平渐变背景？

Question

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。

如何创建具有水平渐变背景的导航栏？

Answer 1

如果您想以编程方式设置给定UINavigationBar的渐变，我会为您提供解决方案。

首先使用您想要的颜色和位置设置CAGradientLayer。

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);

然后抓取该图层的UImage。

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

将gradientImage设置为UINavigationBar的背景图像。

[navigationBar setBackgroundImage:gradientImage forBarMetrics:UIBarMetricsDefault];

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)

Answer 2

更新了适用于iOS 10 / swift 3.0的@JulianM答案：

let gradientLayer = CAGradientLayer()
var updatedFrame = self.navigationController!.navigationBar.bounds
updatedFrame.size.height += 20
gradientLayer.frame = updatedFrame
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)

UIGraphicsBeginImageContext(gradientLayer.bounds.size)
gradientLayer.render(in: UIGraphicsGetCurrentContext()!)
let image = UIGraphicsGetImageFromCurrentImageContext()
UIGraphicsEndImageContext()

self.navigationController!.navigationBar.setBackgroundImage(image, for: UIBarMetrics.default)

Answer 3

您可以使用：

[[UINavigationBar appearance] setBackgroundImage:[UIImage imageNamed:@"gardientImage"] forBarMetrics:UIBarMetricsDefault];

for ios 7导航栏高度为64px

Answer 4

迅速

在全局类中添加此功能

func setHorizontalGradientColor(view: UIView) {
    let gradientLayer = CAGradientLayer()
    var updatedFrame = view.bounds
    updatedFrame.size.height += 20
    gradientLayer.frame = updatedFrame
    gradientLayer.colors = [UIColor.black.cgColor, UIColor.blue.cgColor]
    gradientLayer.startPoint = CGPoint(x: 0.0, y: 0.5)
    gradientLayer.endPoint = CGPoint(x: 1.0, y: 0.5)
    view.layer.insertSublayer(gradientLayer, at: 0)
}

在任何地方使用：

setHorizontalGradientColor(view: self.bgView)