iOS : Touch Id is not shown when AppDelegate's open url is invoked

Question

我的应用程序支持打开来自其他应用程序的图像、pdf 等文档。Tocuh Id的实现如下图，当应用进入前台时请求

NotificationCenter.default.addObserver(forName: .UIApplicationWillEnterForeground, object: nil, queue: .main) { (notification) in
        LAContext().evaluatePolicy( .deviceOwnerAuthenticationWithBiometrics, localizedReason: "Request Touch ID", reply: { [unowned self] (success, error) -> Void in
             if (success) {

             } else {

             }
})

现在，当用户从后台打开应用程序或重新启动时，请求 Touch Id 可以正常工作。当从其他应用程序打开应用程序时会出现此问题，例如点击应用程序 URL，使用“复制到 MyApp”选项从外部应用程序共享文档，其中调用 AppDelegate 的打开 url 方法，如下所示

public func application(_ app: UIApplication, open url: URL, options: [UIApplicationOpenURLOptionsKey : Any] = [:]) -> Bool {
    //validate and save url
    return true
}

问题是当应用程序从外部应用程序启动时，上面的 open url 方法被调用，UIApplicationWillEnterForeground 观察器也按预期被调用。但是在那个 UIApplicationWillEnterForeground 观察者中，LAContext().evaluatePolicy 突然失败并出现错误“Caller moved to background”。

请注意，问题可以在 iOS 11.0.3、11.3 上看到，而在 iOS 11.4 或 <11

上无法重现

Answer 1

你需要在应用程序为 applicationDidBecomeActive 时添加它

NotificationCenter.default.addObserver(forName: .UIApplicationDidBecomeActive, object: nil, queue: .main) { (notification) in

let context = LAContext()

var error: NSError?

if context.canEvaluatePolicy(
    LAPolicy.deviceOwnerAuthenticationWithBiometrics,
    error: &error) {

    // Device can use biometric authentication
    context.evaluatePolicy(
        LAPolicy.deviceOwnerAuthenticationWithBiometrics,
        localizedReason: "Access requires authentication",
        reply: {(success, error) in
            DispatchQueue.main.async {

                if let err = error {

                    switch err._code {

                    case LAError.Code.systemCancel.rawValue:
                        self.notifyUser("Session cancelled",
                                        err: err.localizedDescription)

                    case LAError.Code.userCancel.rawValue:
                        self.notifyUser("Please try again",
                                        err: err.localizedDescription)

                    case LAError.Code.userFallback.rawValue:
                        self.notifyUser("Authentication",
                                        err: "Password option selected")
                        // Custom code to obtain password here

                    default:
                        self.notifyUser("Authentication failed",
                                        err: err.localizedDescription)
                    }

                } else {
                    self.notifyUser("Authentication Successful",
                                    err: "You now have full access")
                }
            }
    })

}

})