我在 IOS 應用程式中顯示視圖控制器時遇到了一些問題。有時它可以作業并顯示視圖，但有時我猜當背景關系有點不同時它不起作用。除錯器中沒有錯誤或警告，它可以從主故事板中找到 ViewController（至少它不是 nil）它曾經與 self.present 一起作業，但似乎不再起作用。
@IBAction func showHistoryButton(_ sender: MDCButton) {
let exercisesHistoryVC = ExercisesHistoryViewController.instantiate(from: .Main)
exercisesHistoryVC.modalPresentationStyle = .fullScreen
let appDeligate = UIApplication.shared.delegate as! AppDelegate
appDeligate.window?.rootViewController!.present(exercisesHistoryVC,animated: true,completion: nil)
// parent?.present(exercisesHistoryVC, animated: true, completion: nil)
}
uj5u.com熱心網友回復：
使用如下代碼，同時顯示新的視圖控制器
@IBAction func showHistoryButton(_ sender: MDCButton) {
let exercisesHistoryVC = ExercisesHistoryViewController.instantiate(from: .Main)
exercisesHistoryVC.modalPresentationStyle = .fullScreen
UIApplication.topViewController()?.present(exercisesHistoryVC, animated: false, completion: nil)
}
extension UIApplication {
static func topViewController(base: UIViewController? = UIApplication.shared.delegate?.window??.rootViewController) -> UIViewController? {
if let nav = base as? UINavigationController {
return topViewController(base: nav.visibleViewController)
}
if let tab = base as? UITabBarController, let selected = tab.selectedViewController {
return topViewController(base: selected)
}
if let presented = base?.presentedViewController {
return topViewController(base: presented)
}
return base
}
}
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