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
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
其他回答
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
对于Objective-C解决方案也是如此
@implementation UIWindow (iOS13)
+ (UIWindow*) keyWindow {
NSPredicate *isKeyWindow = [NSPredicate predicateWithFormat:@"isKeyWindow == YES"];
return [[[UIApplication sharedApplication] windows] filteredArrayUsingPredicate:isKeyWindow].firstObject;
}
@end
理想情况下，由于它已经被弃用，我建议你将窗口存储在SceneDelegate中。但是，如果您确实想要一个临时的解决方案，您可以创建一个过滤器并像这样检索keyWindow。
let window = UIApplication.shared.windows.filter {$0.isKeyWindow}.first
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
当.foregroundActive场景为空时，我遇到了这个问题
这是我的变通办法
public extension UIWindow {
@objc
static var main: UIWindow {
// Here we sort all the scenes in order to work around the case
// when no .foregroundActive scenes available and we need to look through
// all connectedScenes in order to find the most suitable one
let connectedScenes = UIApplication.shared.connectedScenes
.sorted { lhs, rhs in
let lhs = lhs.activationState
let rhs = rhs.activationState
switch lhs {
case .foregroundActive:
return true
case .foregroundInactive:
return rhs == .background || rhs == .unattached
case .background:
return rhs == .unattached
case .unattached:
return false
@unknown default:
return false
}
}
.compactMap { $0 as? UIWindowScene }
guard connectedScenes.isEmpty == false else {
fatalError("Connected scenes is empty")
}
let mainWindow = connectedScenes
.flatMap { $0.windows }
.first(where: \.isKeyWindow)
guard let window = mainWindow else {
fatalError("Couldn't get main window")
}
return window
}
}
