ios - 尝试在演示过程中显示 UIViewController!-警告

Question

假设一个新的 iOS 项目，只有一个导航 Controller (正确连接为入口点)和一个包含以下三行代码的重写 viewDidAppear():

            self.presentViewController(UIViewController(), animated: true, completion: nil)
            self.dismissViewControllerAnimated(true, completion: {})
            self.presentViewController(UIViewController(), animated: true, completion: nil)

执行时，该代码将发出警告“在演示过程中尝试显示 UIViewController!”尝试展示第二个 Controller 时。

问题:为了在调用另一个 Controller 之前正确关闭 Controller ，我究竟缺少什么？

Answer 1

您需要在最初的 presentViewController 调用上添加某种延迟，如下所示:

override func viewDidAppear(animated: Bool) {
    presentViewController(UIViewController(), animated: true) { () -> Void in
        self.delay(0.1, closure: { () -> () in
            self.dismissViewControllerAnimated(true, completion: nil)
        })
    }
}


func delay(delay:Double, closure:()->()) {
    dispatch_after(
        dispatch_time(
            DISPATCH_TIME_NOW,
            Int64(delay * Double(NSEC_PER_SEC))
        ),
        dispatch_get_main_queue(), closure)
}

似乎在动画真正完成之前调用了完成 block 。