Question

我似乎无法在启动视图时弹出警报视图。代码如下。

import UIKit

class StartController: UIViewController
{
    override func viewDidLoad()
    {
        super.viewDidLoad()

        self.view.backgroundColor = UIColor.white;

        startTest();
    }

    func startTest()
    {
        let alerta = UIAlertController(title: "Invalid Test", message: "Testing alert controller", preferredStyle: UIAlertControllerStyle.alert);

        alerta.addAction(UIAlertAction(title: "OK", style: UIAlertActionStyle.default, handler: nil));

        self.present(alerta, animated: true, completion: nil);
    }
}

Answer 1

问题是在viewDidLoad中，视图层次结构未完全设置。如果使用viewDidAppear，则设置层次结构。

如果您真的想在viewDidLoad中调用此警报，可以通过将演示文稿调用包装在此GCD块中来导致轻微延迟

 DispatchQueue.main.async {
    // Run UI Updates or call completion block
      startTest()
 }

或在

中使用

override func viewDidAppear(_ animated: Bool) {
    super.viewDidAppear(animated)
    startTest()
}

Answer 2

在startTest()方法中调用viewDidAppear。它对我有用。

override func viewDidAppear(_ animated: Bool) {
    super.viewDidAppear(animated)
    startTest()
}


func startTest()
{
    let alerta = UIAlertController(title: "Invalid Test", message: "Testing alert controller", preferredStyle: UIAlertControllerStyle.alert);

    alerta.addAction(UIAlertAction(title: "OK", style: UIAlertActionStyle.default, handler: nil));

    self.present(alerta, animated: true, completion: nil);
}

Answer 3

试着把它放在viewDidAppear:方法

上

override func viewDidAppear(_ animated: Bool)  {
      super.viewDidAppear(animated)
       startTest()
}

UIAlertController在swift 3中的启动视图中不起作用

3 个答案: