ios - 如何从委托(delegate)方法启动 UIAlertController?
<p><p>我的代码非常基础。我有 2 个 ViewController 。在名为“FirstScreen”的第一个 viewController 上有一个按钮,通过模态 segue 将我带到第二个屏幕,那里还有一个按钮。 “SecondScreen”有一个带有 1 方法的协议(protocol),“FirstScreen”符合该协议(protocol)。所以基本上我试图从该方法调用 <code>UIAlertController</code>,同时按下“SecondScreen”的按钮。结果我得到:</p>
<blockquote>
<p>"Warning: Attempt to present.....on....whose view is not in the window
hierarchy!</p>
</blockquote>
<p>我知道我可以在我的 Storyboard 中嵌入一个导航 Controller 并且警报会起作用,但对我来说不是这样。我也想以这种方式调用警报,因为需要知道 <code>CLAuthorizationStatus</code>。<br/></p>
<blockquote>
<p><strong>So maybe is there any way of getting the status directly from the
"SecondScreen" ?</strong></p>
</blockquote>
<pre><code>import UIKit
import CoreLocation
class FirstScreen: UIViewController {
@IBAction func firstTapped(_ sender: UIButton) {
let selectionVC = storyboard?.instantiateViewController(withIdentifier: "secondVC") as! SecondScreen
present(selectionVC, animated: true, completion: nil)
selectionVC.delegate = self
}
}
extension FirstScreen: LocationPermissionDelegate {
func checkLocationStatus() {
let status = CLLocationManager.authorizationStatus()
if status == CLAuthorizationStatus.notDetermined {
let alert = UIAlertController(title: "Just a message", message: "HEYYY!", preferredStyle: .alert)
let action = UIAlertAction(title: "Dismiss", style: .default, handler: nil)
alert.addAction(action)
present(alert, animated: true)
}
}
}
import Foundation
import UIKit
protocol LocationPermissionDelegate {
func checkLocationStatus()
}
class SecondScreen: UIViewController {
var delegate: LocationPermissionDelegate?
@IBAction func secondTapped(_ sender: UIButton) {
delegate?.checkLocationStatus()
}
}
</code></pre></p>
<br><hr><h1><strong>Best Answer-推荐答案</ strong></h1><br>
<p><p>firstvc目前正在展示</p>
<pre><code>present(selectionVC, animated: true, completion: nil)
</code></pre>
<p>所以你不能在这里显示警报</p>
<pre><code>present(alert, animated: true)
</code></pre>
<p>移动这个</p>
<pre><code>func checkLocationStatus() {
let status = CLLocationManager.authorizationStatus()
if status == CLAuthorizationStatus.notDetermined {
let alert = UIAlertController(title: "Just a message", message: "HEYYY!", preferredStyle: .alert)
let action = UIAlertAction(title: "Dismiss", style: .default, handler: nil)
alert.addAction(action)
present(alert, animated: true)
}
}
</code></pre>
<p>到第二个vc,在那里做演示</p></p>
<p style="font-size: 20px;">关于ios - 如何从委托(delegate)方法启动 UIAlertController?,我们在Stack Overflow上找到一个类似的问题:
<a href="https://stackoverflow.com/questions/54275477/" rel="noreferrer noopener nofollow" style="color: red;">
https://stackoverflow.com/questions/54275477/
</a>
</p>
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