在 Xamarin 表单中调用 DisplayALert() 时出现异常

Question

我尝试使用以下代码在 xamarin 表单中启动警报框，但调用失败并出现以下异常。

private async void ProfileEmailAddressViewModel_UpdatedPersonalDetailsEvent(object source, UpdateEmployeePersonalDetailsCompletedEventArgs e)
    {
        try
        {
            if (e.Result)
            {
                await DisplayAlert("Alert", "You have been alerted", "OK");
            }
        }
        catch (Exception ex)
        {
            throw ex;
        }
    }

异常详细信息：System.Reflection.TargetInvocationException: Exception has been thrown by the target of an invocation. ---> UIKit.UIKitThreadAccessException: UIKit Consistency error: you are calling a UIKit method that can only be invoked from the UI thread. at UIKit.UIApplication.EnsureUIThread () [0x0001a] in /Library/Frameworks/Xamarin.iOS.framework/Versions/12.0.0.15/src/Xamarin.iOS/UIKit/UIApplication.cs:88 at UIKit.UIView.set_BackgroundColor (UIKit.UIColor value) [0x00000] in /Library/Frameworks/Xamarin.iOS.framework/Versions/12.0.0.15/src/Xamarin.iOS/UIKit/UIView.g.cs:2817 at Xamarin.Forms.Platform.iOS.Platform.PresentAlert (Xamarin.Forms.Internals.AlertArguments arguments) [0x0000d]

如果有人遇到类似问题，请告诉我

Answer 1

由于某种原因，您没有从 UI 线程调用它。

将调用包装在BeginInvokeOnMainThread方法中

Device.BeginInvokeOnMainThread (async () => {
    await DisplayAlert("Alert", "You have been alerted", "OK");
});

当您在后台线程上执行某些操作并且想要与 UI 交互时，您将需要BeginInvokeOnMainThread在负责 UI 的主线程上调用它的方法。