xcode - UIAlertViewController 在实际呈现之前显示出一点延迟

Question

我有一个 UIAlertViewController 需要一段时间才能呈现，一段时间后大约需要一秒钟......代码如下。

PFUser.logInWithUsernameInBackground(usernameTextField.text!, password:passwordTextField.text!) {
        (user: PFUser?, error: NSError?) in
        if user != nil{

        self.performSegueWithIdentifier("toMainView", sender: self)

    } else {

        let alert = UIAlertController(title: "Error", message: "Entered User Creditinials Are Incorrect. Please Try Again.", preferredStyle: UIAlertControllerStyle.Alert)

        let action = UIAlertAction(title: "Ok", style: UIAlertActionStyle.Default, handler: { (action: UIAlertAction!) in

        })

        alert.addAction(action)

        self.presentViewController(alert, animated: true, completion: nil)
    }

}

提前谢谢您:)

Answer 1

我稍微改变了你的代码，现在 UIAlertController 立即弹出。我使用了 Parse.com 错误代码；

PFUser.logInWithUsernameInBackground(usernameTextField.text!, password:passwordTextField.text!) {
        (user: PFUser?, error: NSError?) -> Void in
        if user != nil {
            self.performSegueWithIdentifier("toMainView", sender: self)
        } else {
            let ErrorCode = error!.code
            switch ErrorCode {
            case 101:
                let alert = UIAlertController(title: "Error", message: "Entered User Creditinials Are Incorrect. Please Try Again.", preferredStyle: UIAlertControllerStyle.Alert)
                let action = UIAlertAction(title: "OK", style: UIAlertActionStyle.Default, handler:{ (action: UIAlertAction!) in })
                alert.addAction(action)
                self.presentViewController(alert, animated: true, completion: nil)
                break
            default:
                println(ErrorCode)
                break
            }

        }
    }

您可以看到解析错误代码here .