Swift修改UISearchBar中选中ScopeBar按钮的背景色

我刚接触Swift，目前尝试修改UISearchBar中选中状态下ScopeBar按钮的背景色，当前该按钮背景色为白色，想要更换为其他颜色。以下是我用于添加并配置UISearchBar的代码：

private let searchController = UISearchController(searchResultsController: nil)
    
searchController.searchBar.delegate = self
searchController.searchBar.backgroundColor = UIColor(named: "TopicColor")
navigationItem.searchController = searchController
navigationItem.hidesSearchBarWhenScrolling = false
navigationController?.navigationBar.prefersLargeTitles = true
    
let appearance = UINavigationBarAppearance(idiom: .phone)
appearance.largeTitleTextAttributes = [.foregroundColor: UIColor.white]
appearance.titleTextAttributes = [.foregroundColor: UIColor.white]
appearance.backgroundColor = UIColor(named: "TopicColor")
navigationItem.standardAppearance = appearance
navigationItem.scrollEdgeAppearance = appearance
searchController.obscuresBackgroundDuringPresentation = false
searchController.searchBar.placeholder = "Search"
searchController.searchBar.showsScopeBar = true
searchController.searchBar.scopeButtonTitles = ["Movie", "Series"]
    
UIBarButtonItem.appearance(whenContainedInInstancesOf:[UISearchBar.self]).tintColor = UIColor(named: "Color-1")

let placeholderAppearance = UILabel.appearance(whenContainedInInstancesOf: [UISearchBar.self])
placeholderAppearance.textColor = UIColor.white
    
let searchTextAppearance = UITextField.appearance(whenContainedInInstancesOf: [UISearchBar.self])
searchTextAppearance.textColor = UIColor.white

searchController.searchBar.tintColor = UIColor.white
    
searchController.searchBar.setScopeBarButtonTitleTextAttributes([NSAttributedString.Key.foregroundColor: UIColor(named: "Color-1")!], for: UIControl.State.normal)

解决方案 #

方法1：利用UIAppearance统一设置（iOS 13+） #

ScopeBar本质是UISegmentedControl，可以通过外观代理针对嵌套在UISearchBar里的分段控件设置选中背景色：

// 工具方法：用颜色生成纯色图片
extension UIImage {
    static func imageWithColor(color: UIColor) -> UIImage? {
        let rect = CGRect(x: 0, y: 0, width: 1, height: 1)
        UIGraphicsBeginImageContext(rect.size)
        let context = UIGraphicsGetCurrentContext()
        context?.setFillColor(color.cgColor)
        context?.fill(rect)
        let image = UIGraphicsGetImageFromCurrentImageContext()
        UIGraphicsEndImageContext()
        return image
    }
}

// 在配置SearchBar的代码后添加以下设置
if let selectedBgImage = UIImage.imageWithColor(color: UIColor(named: "YourTargetColor")!) {
    // 设置选中状态的背景图
    UISegmentedControl.appearance(whenContainedInInstancesOf: [UISearchBar.self]).setBackgroundImage(selectedBgImage, for: .selected, barMetrics: .default)
    
    // 可选：设置分割线颜色，避免出现默认白色分割线
    UISegmentedControl.appearance(whenContainedInInstancesOf: [UISearchBar.self]).setDividerImage(selectedBgImage, forLeftSegmentState: .normal, rightSegmentState: .selected, barMetrics: .default)
    UISegmentedControl.appearance(whenContainedInInstancesOf: [UISearchBar.self]).setDividerImage(selectedBgImage, forLeftSegmentState: .selected, rightSegmentState: .normal, barMetrics: .default)
}

方法2：遍历子视图定位控件（兼容旧版本） #

如果需要兼容iOS 13以下系统，可以通过递归遍历SearchBar的子视图找到对应的UISegmentedControl：

// 递归查找ScopeBar对应的分段控件
func findScopeSegmentedControl(in view: UIView) -> UISegmentedControl? {
    for subview in view.subviews {
        if let segmentedControl = subview as? UISegmentedControl {
            return segmentedControl
        } else if let found = findScopeSegmentedControl(in: subview) {
            return found
        }
    }
    return nil
}

// 在viewDidAppear或者searchBar回调中调用（确保ScopeBar已加载）
override func viewDidAppear(_ animated: Bool) {
    super.viewDidAppear(animated)
    if let scopeSegment = findScopeSegmentedControl(in: searchController.searchBar) {
        let targetColor = UIColor(named: "YourTargetColor")!
        let selectedBgImage = UIImage.imageWithColor(color: targetColor)
        scopeSegment.setBackgroundImage(selectedBgImage, for: .selected, barMetrics: .default)
        
        // 可选：设置分割线
        scopeSegment.setDividerImage(selectedBgImage, forLeftSegmentState: .normal, rightSegmentState: .selected, barMetrics: .default)
        scopeSegment.setDividerImage(selectedBgImage, forLeftSegmentState: .selected, rightSegmentState: .normal, barMetrics: .default)
    }
}

补充：调整选中状态的文字颜色 #

如果需要同步修改选中按钮的文字颜色，添加以下代码：

searchController.searchBar.setScopeBarButtonTitleTextAttributes([
    NSAttributedString.Key.foregroundColor: UIColor.white // 替换为你需要的文字颜色
], for: .selected)

内容的提问来源于stack exchange，提问作者Kolykhalov Stas