我使用核心数据与云工具包，因此要检查iCloud用户状态在应用程序启动。如果出现问题，我想向用户发出一个对话框，我使用UIApplication.shared.keyWindow?. rootviewcontroller ?.present(…)到目前为止。
在Xcode 11 beta 4中，现在有一个新的弃用消息，告诉我:
'keyWindow'在iOS 13.0中已弃用:不应该用于支持多个场景的应用程序，因为它在所有连接的场景中返回一个键窗口
我应该如何呈现对话呢?
当前回答
Objective C解决方案:
UIWindow *foundWindow = nil;
NSSet *scenes=[[UIApplication sharedApplication] connectedScenes];
NSArray *windows;
for(id aScene in scenes){ // it's an NSSet so you can't use the first object
windows=[aScene windows];
if([aScene activationState]==UISceneActivationStateForegroundActive)
break;
}
for (UIWindow *window in windows) {
if (window.isKeyWindow) {
foundWindow = window;
break;
}
}
// and to find the parent viewController:
UIViewController* parentController = foundWindow.rootViewController;
while( parentController.presentedViewController &&
parentController != parentController.presentedViewController ){
parentController = parentController.presentedViewController;
}
其他回答
Objective C解决方案:
UIWindow *foundWindow = nil;
NSSet *scenes=[[UIApplication sharedApplication] connectedScenes];
NSArray *windows;
for(id aScene in scenes){ // it's an NSSet so you can't use the first object
windows=[aScene windows];
if([aScene activationState]==UISceneActivationStateForegroundActive)
break;
}
for (UIWindow *window in windows) {
if (window.isKeyWindow) {
foundWindow = window;
break;
}
}
// and to find the parent viewController:
UIViewController* parentController = foundWindow.rootViewController;
while( parentController.presentedViewController &&
parentController != parentController.presentedViewController ){
parentController = parentController.presentedViewController;
}
NSSet *connectedScenes = [UIApplication sharedApplication].connectedScenes;
for (UIScene *scene in connectedScenes) {
if (scene.activationState == UISceneActivationStateForegroundActive && [scene isKindOfClass:[UIWindowScene class]]) {
UIWindowScene *windowScene = (UIWindowScene *)scene;
for (UIWindow *window in windowScene.windows) {
UIViewController *viewController = window.rootViewController;
// Get the instance of your view controller
if ([viewController isKindOfClass:[YOUR_VIEW_CONTROLLER class]]) {
// Your code here...
break;
}
}
}
}
如果你想在任何ViewController中使用它，那么你可以简单地使用。
self.view.window
一个UIApplication扩展:
extension UIApplication {
/// The app's key window taking into consideration apps that support multiple scenes.
var keyWindowInConnectedScenes: UIWindow? {
return windows.first(where: { $0.isKeyWindow })
}
}
用法:
let myKeyWindow: UIWindow? = UIApplication.shared.keyWindowInConnectedScenes
如果你的应用还没有更新到采用基于场景的应用生命周期，另一种获得活动窗口对象的简单方法是通过UIApplicationDelegate:
let window = UIApplication.shared.delegate?.window
let rootViewController = window??.rootViewController
