如何使用渐变颜色设置UINavigationbar？

I want to set the UINavigationbar backgroundColor to a gradient color where I would like to set it via an array of colors to create a Gradient, ideally, as accessible methods inside UINavigationBar to change its color to this gradient.

我想将UINavigationbar backgroundColor设置为渐变颜色，我想通过颜色数组来设置它，以创建一个渐变，理想情况下，作为UINavigationBar中的可访问方法，将其颜色更改为此渐变。

Any suggestions? (Aside from setting an image manually as the background image of the navigation bar)

有什么建议么？ （除了手动设置图像作为导航栏的背景图像）

6 个解决方案

#1

Create gradient layer and add it as background of navigation bar.

创建渐变图层并将其添加为导航栏的背景。

    CAGradientLayer *gradient = [CAGradientLayer layer];
    gradient.frame = self.navigationController.navigationBar.bounds;
    gradient.colors = [NSArray arrayWithObjects:(id)[[UIColor whiteColor] CGColor], (id)[[UIColor blackColor] CGColor], nil];
    [self.navigationController.navigationBar setBackgroundImage:[self imageFromLayer:gradient] forBarMetrics:UIBarMetricsDefault];

For creating image from layer.

用于从图层创建图像。

- (UIImage *)imageFromLayer:(CALayer *)layer
{
    UIGraphicsBeginImageContext([layer frame].size);

    [layer renderInContext:UIGraphicsGetCurrentContext()];
    UIImage *outputImage = UIGraphicsGetImageFromCurrentImageContext();

    UIGraphicsEndImageContext();

    return outputImage;
}

One more thing, there is one library available in github : CRGradientNavigationBar you can also use this library.

还有一件事，github中有一个库：CRGradientNavigationBar你也可以使用这个库。

#2

Details

Xcode 8.3.1, Swift 3.1

Xcode 8.3.1，Swift 3.1

Code

extension CAGradientLayer

扩展CAGradientLayer

extension CAGradientLayer {

    convenience init(frame: CGRect, colors: [UIColor]) {
        self.init()
        self.frame = frame
        self.colors = []
        for color in colors {
            self.colors?.append(color.cgColor)
        }
        startPoint = CGPoint(x: 0, y: 0)
        endPoint = CGPoint(x: 0, y: 1)
    }

    func createGradientImage() -> UIImage? {

        var image: UIImage? = nil
        UIGraphicsBeginImageContext(bounds.size)
        if let context = UIGraphicsGetCurrentContext() {
            render(in: context)
            image = UIGraphicsGetImageFromCurrentImageContext()
        }
        UIGraphicsEndImageContext()
        return image
    }

}

extension UINavigationBar

扩展UINavigationBar

extension UINavigationBar {

    func setGradientBackground(colors: [UIColor]) {

        var updatedFrame = bounds
        updatedFrame.size.height += self.frame.origin.y
        let gradientLayer = CAGradientLayer(frame: updatedFrame, colors: colors)

        setBackgroundImage(gradientLayer.createGradientImage(), for: UIBarMetrics.default)
    }
}

Usage

class ViewController

class ViewController

import UIKit

class ViewController: UIViewController {

    override func viewDidLoad() {
        super.viewDidLoad()

        var colors = [UIColor]()
        colors.append(UIColor(red: 221/255, green: 34/255, blue: 13/255, alpha: 1))
        colors.append(UIColor(red: 247/255, green: 113/255, blue: 98/255, alpha: 1))
        navigationController?.navigationBar.setGradientBackground(colors: colors)
    }
}

Main.storyboard

Main.storyboard

Result

#3

In Swift 3 and Swift 4:

在Swift 3和Swift 4中：

let gradient = CAGradientLayer()
let sizeLength = UIScreen.main.bounds.size.height * 2
let defaultNavigationBarFrame = CGRect(x: 0, y: 0, width: sizeLength, height: 64)

gradient.frame = defaultNavigationBarFrame

gradient.colors = [UIColor.white.cgColor, UIColor.black.cgColor]

UINavigationBar.appearance().setBackgroundImage(self.image(fromLayer: gradient), for: .default)

For creating image from layer:

从图层创建图像：

func image(fromLayer layer: CALayer) -> UIImage {
    UIGraphicsBeginImageContext(layer.frame.size)

    layer.render(in: UIGraphicsGetCurrentContext()!)

    let outputImage = UIGraphicsGetImageFromCurrentImageContext()

    UIGraphicsEndImageContext()

    return outputImage!
}

In Swift 2:

在Swift 2中：

let gradient = CAGradientLayer()
let sizeLength = UIScreen.mainScreen().bounds.size.height * 2
let defaultNavigationBarFrame = CGRectMake(0, 0, sizeLength, 64)

gradient.frame = defaultNavigationBarFrame

gradient.colors = [UIColor.whiteColor().CGColor, UIColor.blackColor().CGColor]

UINavigationBar.appearance().setBackgroundImage(self.image(fromLayer: gradient), forBarMetrics: .Default)

For creating image from layer:

从图层创建图像：

func image(fromLayer layer: CALayer) -> UIImage {    
    UIGraphicsBeginImageContext(layer.frame.size)

    layer.renderInContext(UIGraphicsGetCurrentContext()!)

    let outputImage = UIGraphicsGetImageFromCurrentImageContext()

     UIGraphicsEndImageContext()

    return outputImage!
}

#4

This is the solution without using an intermediate CAGradientLayer, and just using CoreGraphics, in Swift 3.0.

这是不使用中间CAGradientLayer的解决方案，只是在Swift 3.0中使用CoreGraphics。

Essentially, the method creates a UIImage on the fly with the gradient colors passed and sets it.

本质上，该方法动态创建UIImage，并传递渐变颜色并设置它。

extension UINavigationBar
{
    /// Applies a background gradient with the given colors
    func apply(gradient colors : [UIColor]) {
        var frameAndStatusBar: CGRect = self.bounds
        frameAndStatusBar.size.height += 20 // add 20 to account for the status bar

        setBackgroundImage(UINavigationBar.gradient(size: frameAndStatusBar.size, colors: colors), for: .default)
    }

    /// Creates a gradient image with the given settings
    static func gradient(size : CGSize, colors : [UIColor]) -> UIImage?
    {
        // Turn the colors into CGColors
        let cgcolors = colors.map { $0.cgColor }

        // Begin the graphics context
        UIGraphicsBeginImageContextWithOptions(size, true, 0.0)

        // If no context was retrieved, then it failed
        guard let context = UIGraphicsGetCurrentContext() else { return nil }

        // From now on, the context gets ended if any return happens
        defer { UIGraphicsEndImageContext() }

        // Create the Coregraphics gradient
        var locations : [CGFloat] = [0.0, 1.0]
        guard let gradient = CGGradient(colorsSpace: CGColorSpaceCreateDeviceRGB(), colors: cgcolors as NSArray as CFArray, locations: &locations) else { return nil }

        // Draw the gradient
        context.drawLinearGradient(gradient, start: CGPoint(x: 0.0, y: 0.0), end: CGPoint(x: size.width, y: 0.0), options: [])

        // Generate the image (the defer takes care of closing the context)
        return UIGraphicsGetImageFromCurrentImageContext()
    }
}

The defer statement makes this so much clean than prior versions. Be noted that CGGradient are available since iOS 8.0.

延迟语句使得它比以前的版本更加干净。请注意，CGGradient自iOS 8.0起可用。

Also, this creates the gradient from left to right, tweaking the parameters of drawLinearGradient (start and end) moves the locations. This is up for your implementation.

此外，这将创建从左到右的渐变，调整drawLinearGradient（开始和结束）的参数移动位置。这取决于您的实施。

#5

In Swift 3

在Swift 3中

let gradient = CAGradientLayer()
let sizeLength = UIScreen.main.bounds.size.height * 2
let defaultNavigationBarFrame = CGRect(x: 0, y: 0, width: sizeLength, height: 64)
gradient.frame = defaultNavigationBarFrame
gradient.colors = [UIColor.white.cgColor, UIColor.black.cgColor]
UINavigationBar.appearance().setBackgroundImage(self.image(fromLayer: gradient), for: .default)

func image(fromLayer layer: CALayer) -> UIImage {
    UIGraphicsBeginImageContext(layer.frame.size)
    layer.render(in: UIGraphicsGetCurrentContext()!)
    let outputImage = UIGraphicsGetImageFromCurrentImageContext()
    UIGraphicsEndImageContext()
    return outputImage!
}

#6

Objective C solution that works on iPhone X as well:

适用于iPhone X的Objective C解决方案：

- (void)addGradientToNavigationBar
{
    CAGradientLayer *gradient = [CAGradientLayer layer];
    CGRect gradientFrame = self.navigationController.navigationBar.bounds;
    gradientFrame.size.height += [UIApplication sharedApplication].statusBarFrame.size.height;
    gradient.frame = gradientFrame;
    gradient.colors = [NSArray arrayWithObjects:(id)[[UIColor colorGradientUp] CGColor], (id)[[UIColor colorGradientDown] CGColor], nil];
    [self.navigationController.navigationBar setBackgroundImage:[self imageFromLayer:gradient] forBarMetrics:UIBarMetricsDefault];
}

- (UIImage *)imageFromLayer:(CALayer *)layer
{
    UIGraphicsBeginImageContext([layer frame].size);

    [layer renderInContext:UIGraphicsGetCurrentContext()];
    UIImage *outputImage = UIGraphicsGetImageFromCurrentImageContext();

    UIGraphicsEndImageContext();

    return outputImage;
}