NSInternalInconsistencyException: 只能有一个 UIApplication 实例

Question

描述：

正在尝试使用 UIApplication class 在我的应用程序中打开 Youtube URL。

let url = URL(string: "https://www.youtube.com/watch?v=smOp5aK-_h0")!
let app = UIApplication()
if app.canOpenURL(url){
  //Crash here
  app.openURL(url)
}

问题：

为什么当我尝试打开 url 时我的应用程序崩溃？

错误：

* Assertion failure in -[UIApplication init], * Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'There can only be one UIApplication instance.'

编辑：不崩溃但不打开 link:

       if UIApplication.shared.canOpenURL(url){
            print("Can open shared application url.")
            if #available(tvOS 10.0, *) {
                print("tvOS 10.0 detected")
                UIApplication.shared.open(url){res in
                    //res is false... 
                    print("Result..." + String(res))
                }
            } else {
                // Fallback on earlier versions
                UIApplication.shared.openURL(url)
            }
        }

Answer 1

错误说的很清楚。您必须使用默认应用程序。 UIApplication.shared.canOpenURL(url)

Answer 2

错误是说：

There can only be one UIApplication instance

意味着应该调用一个实例，当使用 UIApplication 时，它应该是 shared （单例）实例。如UIApplication's Documentation所述：

The UIApplication class provides a centralized point of control and coordination for apps running in iOS. Every app has exactly one instance of UIApplication (or, very rarely, a subclass of UIApplication). When an app is launched, the system calls the UIApplicationMain(::::) function; among its other tasks, this function creates a Singleton UIApplication object. Thereafter you access the object by calling the shared() class method.

共享():

All UIApplication notifications are posted by the app instance returned by shared().

那么你需要做的就是把let app = UIApplication()改成let app = UIApplication.shared:

let url = URL(string: "https://www.youtube.com/watch?v=smOp5aK-_h0")!
let app = UIApplication.shared
if app.canOpenURL(url) {
    app.open(url, options: [:], completionHandler: nil)
}

或：

// for being safe, I suggest also to do "optional-binding" for the url:
if let url = URL(string: "https://www.youtube.com/watch?v=smOp5aK-_h0") {
    if UIApplication.shared.canOpenURL(url) {
        UIApplication.shared.open(url, options: [:], completionHandler: nil)
    }
}

NSInternalInconsistencyException: 只能有一个 UIApplication 实例

NSInternalInconsistencyException: There can only be one UIApplication instance

ios

swift

tvos

swift3

描述：

问题：

错误：