iOS开发：如何消除searchBar与searchResultsController间空白并让结果控制器紧贴搜索栏

开发过程中UISearchBar与searchResultsController展示时存在额外空白，效果如下：

if #available(iOS 11, *) {
    let searchController = UISearchController(searchResultsController: ResultsController())
    searchController.searchBar.backgroundColor = UIColor.Custom.theme
    searchController.searchBar.delegate = self
    searchController.searchResultsUpdater = self
    navigationItem.searchController = searchController
    navigationItem.hidesSearchBarWhenScrolling = false
}

iOS 11+ 将UISearchController关联到navigationItem后，系统会默认对searchResultsController的视图自动适配安全区域内边距，最终导致结果视图顶部出现多余空白。

• 方案1：在ResultsController的viewDidLoad方法中禁用自动内边距调整

override func viewDidLoad() {
    super.viewDidLoad()
    if #available(iOS 11.0, *) {
        // 清空额外安全区域内边距
        additionalSafeAreaInsets = .zero
        // 如果结果控制器根视图是滚动视图，禁用自动内边距调整
        if let scrollView = view as? UIScrollView {
            scrollView.contentInsetAdjustmentBehavior = .never
        }
    }
}

• 方案2：修改现有初始化代码，新增属性配置

if #available(iOS 11, *) {
    let searchController = UISearchController(searchResultsController: ResultsController())
    searchController.searchBar.backgroundColor = UIColor.Custom.theme
    searchController.searchBar.delegate = self
    searchController.searchResultsUpdater = self
    // 新增配置：设置searchBar不透明，避免视图偏移计算异常
    searchController.searchBar.isTranslucent = false
    // 新增配置：设置当前控制器为上下文定义方，避免结果视图层级异常
    definesPresentationContext = true
    navigationItem.searchController = searchController
    navigationItem.hidesSearchBarWhenScrolling = false
}

• 方案3：通过代理手动修正结果视图位置
  先为searchController设置代理：
  searchController.delegate = self
  再实现UISearchControllerDelegate代理方法：

func willPresentSearchController(_ searchController: UISearchController) {
    DispatchQueue.main.async {
        guard let resultsVC = searchController.searchResultsController else { return }
        let searchBarMaxY = self.navigationController?.navigationBar.frame.maxY ?? 0
        resultsVC.view.frame = CGRect(
            x: 0,
            y: searchBarMaxY,
            width: self.view.bounds.width,
            height: self.view.bounds.height - searchBarMaxY
        )
    }
}

内容的提问来源于stack exchange，提问作者aaajiulong