我为 UIAlertViewController 声明了一个全局变量,以便我能够在我的类中以不同的方法显示和关闭它。我显示了两种警报:第一,带有按钮的警报,当遇到错误时会显示或显示信息消息。第二个是没有按钮的警报,它将像进度消息一样显示。
这是示例代码:
private var alert: UIAlertController? // global declaration
private func showProgressMessage(sender viewController: UIViewController, message alertMessage: String)
{
DispatchQueue.main.async
{
self.alert= UIAlertController(title: "", message: alertMessage, preferredStyle: .alert)
viewController.present(self.alert!, animated: true, completion: nil)
}
}
private func showAlertMessage(sender viewController: UIViewController, title alertTitle: String, message alertMessage: String)
{
DispatchQueue.main.async
{
self.alert= UIAlertController(title: alertTitle, message: alertMessage, preferredStyle: .alert)
self.alert!.addAction(UIAlertAction(title: "OK", style: .default, handler: nil))
viewController.present(self.alert!, animated: true, completion: nil)
}
}
private func method1()
{
DispatchQueue.global().async
{
// some code here
self.showProgressMessage(sender: self, message: "Processing...")
// some code here
}
}
private func method2()
{
// some code here
self.alert!.dismiss(animated: false)
{
self.showAlertMessage(sender: self, message: "Done")
}
self.displayOtherViewController()
}
private func displayOtherViewController()
{
self.alert?.dismiss(animated: false)
{
if let viewController = self.storyboard?.instantiateViewController(withIdentifier: "Sample")
{
let view = viewController as! SampleViewController
view .modalTransitionStyle = .crossDissolve
self.present(view , animated: true, completion: nil)
}
}
}
在方法2中,再次显示警报需要几秒钟才能显示,与视图控制器相同。在 Swift 4 中显示和关闭 UIAlertController 的正确方法是什么?
似乎您的代码是从后台线程启动的。甚至必须在主线程上调用dismiss试试这个:
private func method2() {
DispatchQueue.main.async {
self.alert!.dismiss(animated: false) {
self.showAlertMessage(sender: self, message: "Done")
}
self.displayOtherViewController()
}
}
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