我怎样才能让 UIAlertController 出现在任何东西的顶部？

Question

我正在开发一个使用 Visual Studio 2022 的应用程序，它使用 ZXing.Net.Mobile,Forms 扫描条形码，一切都按预期工作，除了我无法在所有内容的顶部显示 UIAlertController 消息。我的代码是：

        btnScan.TouchUpInside += (object sender, EventArgs e) =>
        {
            // First we must get permission to use the camera
            AVAuthorizationStatus authStatus = AVCaptureDevice.GetAuthorizationStatus(AVAuthorizationMediaType.Video);

            if (authStatus == AVAuthorizationStatus.Authorized)
            {
                scan();
            }
            else if (authStatus == AVAuthorizationStatus.NotDetermined)
            {
                Utils.ShowMessage(this,"Camera access not determined. Ask for permission.", "Error");

                AVCaptureDevice.RequestAccessForMediaType(AVAuthorizationMediaType.Video, (granted) =>
                {
                    if (granted)
                    {
                        scan();
                    }
                    else
                    {
                        camDenied();
                    }
                });
            }
            else if (authStatus == AVAuthorizationStatus.Restricted)
            {
                Utils.ShowMessage(this, "This device doesn't have the camera feature", "Error");
            }
            else
            {
                // Denied
                camDenied();
            }
        };
    }

    void HandleScanResult(ZXing.Result result)
    {
        var msg = "";

        if (result != null && !string.IsNullOrEmpty(result.Text))
            msg = "Found Barcode: " + result.Text;
        else
            msg = "Scanning Canceled!";

        // I need this alert to appear over the top of everything
        InvokeOnMainThread(() =>
        {
            Utils.ShowMessage(this, msg, "Scan Success");
        });
    }
    void camDenied()
    {
        UIAlertController alert = UIAlertController.Create("Warning", "It looks like your privacy settings are preventing us from accessing your camera. You can fix this by doing the following...", UIAlertControllerStyle.Alert);

        UIAlertAction goAction = UIAlertAction.Create("Go", UIAlertActionStyle.Default, (action) =>
        {
            // Open Settings 
            UIApplication.SharedApplication.OpenUrl(new NSUrl(UIApplication.OpenSettingsUrlString));
        });
        alert.AddAction(goAction);

        PresentViewController(alert, true, null);
    }

    void scan ()
    {
        InvokeOnMainThread(() => {
            scanner = new MobileBarcodeScanner(this.NavigationController);
            scanner.UseCustomOverlay = false;
            var opt = new MobileBarcodeScanningOptions() { DelayBetweenContinuousScans = 3000 };
            scanner.TopText = "Hold camera up to barcode to scan";
            scanner.BottomText = "Barcode will automatically scan";

            //Start scanning
            scanner.ScanContinuously(opt, false, HandleScanResult);
        });
    }

UIAlertController 代码执行没有错误，但没有出现警告。有没有办法强制警报显示在所有内容的顶部？

Answer 1

我想通了。我改变了我的 Utils.ShowMessage 函数如下：

    public static void ShowMessage(UIViewController myview, string message, string messagetype)
    {
        var window = UIApplication.SharedApplication.KeyWindow;
        var vc = window.RootViewController;
        while (vc.PresentedViewController != null)
        {
            vc = vc.PresentedViewController;
        }

        var okAlertController = UIAlertController.Create(message, messagetype, UIAlertControllerStyle.Alert);
        okAlertController.AddAction(UIAlertAction.Create("OK", UIAlertActionStyle.Default, null));
        vc.PresentViewController(okAlertController, true, null);
    }

需要获取根视图控制器并从中显示警报。

我怎样才能让 UIAlertController 出现在任何东西的顶部？

How can I make UIAlertController appear over the top of anything and everything?

c#

ios

xamarin.ios

uialertcontroller

visual-studio-2022