[ios] 뷰 컨트롤러에 없을 때 UIAlertController를 표시하는 방법은 무엇입니까?

WWDC에서 랩 중 하나에 들러서 Apple 엔지니어에게 다음과 같은 질문을했습니다. ” UIAlertController? 를 표시하는 가장 좋은 방법은 무엇입니까 ?” 그리고 그는 그들이이 질문을 많이 받고 있다고 말했다. 그리고 우리는 그들이 그것에 관한 세션을 가져야한다고 농담했다. 그는 내부적으로 애플이 UIWindow투명성을 가진 제품을 만들고 그것을 UIViewController제시하고 UIAlertController있다고 말했다. 기본적으로 Dylan Betterman의 답변에는 무엇이 있습니까?

그러나 하위 클래스를 사용하고 싶지 않았으므로 UIAlertController앱 전체에서 코드를 변경해야하기 때문입니다. 그래서 관련된 객체의 도움으로 Objective-C UIAlertController의 show메소드 를 제공하는 카테고리를 만들었습니다 .

관련 코드는 다음과 같습니다.

#import "UIAlertController+Window.h"
#import <objc/runtime.h>

@interface UIAlertController (Window)

- (void)show;
- (void)show:(BOOL)animated;

@end

@interface UIAlertController (Private)

@property (nonatomic, strong) UIWindow *alertWindow;

@end

@implementation UIAlertController (Private)

@dynamic alertWindow;

- (void)setAlertWindow:(UIWindow *)alertWindow {
    objc_setAssociatedObject(self, @selector(alertWindow), alertWindow, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
}

- (UIWindow *)alertWindow {
    return objc_getAssociatedObject(self, @selector(alertWindow));
}

@end

@implementation UIAlertController (Window)

- (void)show {
    [self show:YES];
}

- (void)show:(BOOL)animated {
    self.alertWindow = [[UIWindow alloc] initWithFrame:[UIScreen mainScreen].bounds];
    self.alertWindow.rootViewController = [[UIViewController alloc] init];

    id<UIApplicationDelegate> delegate = [UIApplication sharedApplication].delegate;
    // Applications that does not load with UIMainStoryboardFile might not have a window property:
    if ([delegate respondsToSelector:@selector(window)]) {
        // we inherit the main window's tintColor
        self.alertWindow.tintColor = delegate.window.tintColor;
    }

    // window level is above the top window (this makes the alert, if it's a sheet, show over the keyboard)
    UIWindow *topWindow = [UIApplication sharedApplication].windows.lastObject;
    self.alertWindow.windowLevel = topWindow.windowLevel + 1;

    [self.alertWindow makeKeyAndVisible];
    [self.alertWindow.rootViewController presentViewController:self animated:animated completion:nil];
}

- (void)viewDidDisappear:(BOOL)animated {
    [super viewDidDisappear:animated];

    // precaution to ensure window gets destroyed
    self.alertWindow.hidden = YES;
    self.alertWindow = nil;
}

@end

다음은 샘플 사용법입니다.

// need local variable for TextField to prevent retain cycle of Alert otherwise UIWindow
// would not disappear after the Alert was dismissed
__block UITextField *localTextField;
UIAlertController *alert = [UIAlertController alertControllerWithTitle:@"Global Alert" message:@"Enter some text" preferredStyle:UIAlertControllerStyleAlert];
[alert addAction:[UIAlertAction actionWithTitle:@"OK" style:UIAlertActionStyleDefault handler:^(UIAlertAction *action) {
    NSLog(@"do something with text:%@", localTextField.text);
// do NOT use alert.textfields or otherwise reference the alert in the block. Will cause retain cycle
}]];
[alert addTextFieldWithConfigurationHandler:^(UITextField *textField) {
    localTextField = textField;
}];
[alert show];

UIWindow이 때 생성되는이 파괴됩니다 UIAlertControllerdealloced있다가 유지되는 유일한 객체이기 때문에 UIWindow. 그러나 UIAlertController액션 블록 중 하나에서 경고에 액세스하여 속성에 속성 을 할당 하거나 유지 횟수를 늘리면 UIWindow화면에 그대로 유지되고 UI가 잠 깁니다. 액세스가 필요한 경우를 피하려면 위의 샘플 사용 코드를 참조하십시오 UITextField.

테스트 프로젝트로 깃 허브 저장소를 만들었습니다 : FFGlobalAlertController

답변

let alertController = UIAlertController(title: "title", message: "message", preferredStyle: .alert)
//...
var rootViewController = UIApplication.shared.keyWindow?.rootViewController
if let navigationController = rootViewController as? UINavigationController {
    rootViewController = navigationController.viewControllers.first
}
if let tabBarController = rootViewController as? UITabBarController {
    rootViewController = tabBarController.selectedViewController
}
//...
rootViewController?.present(alertController, animated: true, completion: nil)

UIAlertController *alertController = [UIAlertController alertControllerWithTitle:@"Title" message:@"message" preferredStyle:UIAlertControllerStyleAlert];
//...
id rootViewController = [UIApplication sharedApplication].delegate.window.rootViewController;
if([rootViewController isKindOfClass:[UINavigationController class]])
{
    rootViewController = ((UINavigationController *)rootViewController).viewControllers.firstObject;
}
if([rootViewController isKindOfClass:[UITabBarController class]])
{
    rootViewController = ((UITabBarController *)rootViewController).selectedViewController;
}
//...
[rootViewController presentViewController:alertController animated:YES completion:nil];

let alertController: UIAlertController = ...
UIApplication.sharedApplication().keyWindow?.rootViewController?.presentViewController(alertController, animated: true, completion: nil)

let alertController: UIAlertController = ...
UIApplication.shared.keyWindow?.rootViewController?.present(alertController, animated: true, completion: nil)

//option 1:
myAlertController.show()
//option 2:
myAlertController.present(animated: true) {
    //completion code...
}

//Uses Swift1.2 syntax with the new if-let
// so it won't compile on a lower version.
extension UIAlertController {

    func show() {
        present(animated: true, completion: nil)
    }

    func present(#animated: Bool, completion: (() -> Void)?) {
        if let rootVC = UIApplication.sharedApplication().keyWindow?.rootViewController {
            presentFromController(rootVC, animated: animated, completion: completion)
        }
    }

    private func presentFromController(controller: UIViewController, animated: Bool, completion: (() -> Void)?) {
        if  let navVC = controller as? UINavigationController,
            let visibleVC = navVC.visibleViewController {
                presentFromController(visibleVC, animated: animated, completion: completion)
        } else {
          if  let tabVC = controller as? UITabBarController,
              let selectedVC = tabVC.selectedViewController {
                presentFromController(selectedVC, animated: animated, completion: completion)
          } else {
              controller.presentViewController(self, animated: animated, completion: completion)
          }
        }
    }
}

UIWindow* window = [[UIWindow alloc] initWithFrame:[UIScreen mainScreen].bounds];
window.rootViewController = [UIViewController new];
window.windowLevel = UIWindowLevelAlert + 1;

UIAlertController* alertCtrl = [UIAlertController alertControllerWithTitle:... message:... preferredStyle:UIAlertControllerStyleAlert];

[alertCtrl addAction:[UIAlertAction actionWithTitle:NSLocalizedString(@"OK",@"Generic confirm") style:UIAlertActionStyleCancel handler:^(UIAlertAction * _Nonnull action) {
    ... // do your stuff

    // very important to hide the window afterwards.
    // this also keeps a reference to the window until the action is invoked.
    window.hidden = YES;
}]];

[window makeKeyAndVisible];
[window.rootViewController presentViewController:alertCtrl animated:YES completion:nil];

let alertController = UIAlertController(title: "<your title>", message: "<your message>", preferredStyle: UIAlertControllerStyle.alert)
alertController.addAction(UIAlertAction(title: "Close", style: UIAlertActionStyle.cancel, handler: nil))

let alertWindow = UIWindow(frame: UIScreen.main.bounds)
alertWindow.rootViewController = UIViewController()
alertWindow.windowLevel = UIWindowLevelAlert + 1;
alertWindow.makeKeyAndVisible()
alertWindow.rootViewController?.present(alertController, animated: true, completion: nil)