iOS15下有限图库选择器导航栏颜色设置异常如何解决

问题描述 #

我尝试设置有限图库选择器的导航栏颜色，在AppDelegate.application:didFinishLaunchingWithOptions:方法中添加了如下代码：

if (@available(iOS 13, *)) {
    UINavigationBarAppearance *navigationBarAppearance = [UINavigationBarAppearance new];
    navigationBarAppearance.backgroundColor = UIColor.yellowColor;

    [UINavigationBar appearance].standardAppearance = navigationBarAppearance;
    [UINavigationBar appearance].scrollEdgeAppearance = navigationBarAppearance;
}

[UINavigationBar appearance].barTintColor = UIColor.greenColor;
[UINavigationBar appearance].backgroundColor = UIColor.redColor;

上述代码在iOS14上运行符合预期，导航栏显示为绿色：

但在iOS15上运行时，导航栏显示为淡红色：

补充说明 #

最小可复现示例：新建单视图控制器iOS项目，在info.plist中添加NSPhotoLibraryUsageDescription权限声明，核心代码如下：

import UIKit
import Photos
import PhotosUI

class ViewController: UIViewController {
    override func viewDidLoad() {
        super.viewDidLoad()
        // 视图加载完成后的额外配置
        PHPhotoLibrary.requestAuthorization(for: .readWrite, handler: { _ in})
        PHPhotoLibrary.shared().presentLimitedLibraryPicker(from: self)
    }
}

AppDelegate.swift代码：

import UIKit

@main
class AppDelegate: UIResponder, UIApplicationDelegate {
    func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {
        // 应用启动后自定义配置入口
        if #available(iOS 13, *) {
            let navigationBarAppearance = UINavigationBarAppearance()
            navigationBarAppearance.backgroundColor = UIColor.yellow

            UINavigationBar.appearance().standardAppearance = navigationBarAppearance
            UINavigationBar.appearance().scrollEdgeAppearance = navigationBarAppearance
        }

        UINavigationBar.appearance().barTintColor = UIColor.green
        UINavigationBar.appearance().backgroundColor = UIColor.red
        return true
    }

    // MARK: UISceneSession 生命周期
    func application(_ application: UIApplication, configurationForConnecting connectingSceneSession: UISceneSession, options: UIScene.ConnectionOptions) -> UISceneConfiguration {
        // 新建场景会话时调用，用于选择创建场景的配置
        return UISceneConfiguration(name: "Default Configuration", sessionRole: connectingSceneSession.role)
    }
}

失效原因 #

iOS15开始，UINavigationBar默认开启半透明效果，全局设置的barTintColor、UINavigationBarAppearance.backgroundColor会被系统自带的有限图库选择器的导航栏默认样式叠加半透明遮罩，导致最终显示的颜色与预期不符。

解决方案 #

通过生成1px纯色图片作为导航栏背景图，强制覆盖系统默认渲染逻辑，兼容全iOS版本：

Objective-C 版本 #

UIGraphicsImageRenderer * imageRenderer = [[UIGraphicsImageRenderer alloc]initWithSize:CGSizeMake(1, 1)];
UIImage *image = [imageRenderer imageWithActions:^(UIGraphicsImageRendererContext *context){
    // 替换为你需要的导航栏颜色即可
    [UIColor.greenColor setFill];
    [context fillRect:CGRectMake(0, 0, 1, 1)];
}];
[[UINavigationBar appearance] setBackgroundImage:image forBarMetrics:UIBarMetricsDefault];

Swift 版本 #

let imageRenderer = UIGraphicsImageRenderer(size: CGSize(width: 1, height: 1))
let image = imageRenderer.image { context in
    // 替换为你需要的导航栏颜色即可
    UIColor.green.setFill()
    context.fill(CGRect(x: 0, y: 0, width: 1, height: 1))
}
UINavigationBar.appearance().setBackgroundImage(image, for: .default)

内容的提问来源于stack exchange，提问作者BenJacob