无论我用什么方式编码，都无法在 iPhone 上显示警报，我尝试了 4 种不同的方式

Question

提到的这 4 种方法中，它们都可以在模拟器中使用，但不能在 iPhone 中使用。以下是在这里发挥作用的代码片段。

<ListView x:Name="AutoView" ItemsSource="{Binding AutoData}" SelectedItem="{Binding SelectedItem}" SeparatorVisibility="None"  Grid.Row="1" Grid.ColumnSpan="6" BackgroundColor="Purple">
        <ListView.ItemTemplate>
            <DataTemplate>
                <ViewCell>
                    <ViewCell.View>
                        <Grid>
                            <Grid.RowDefinitions>
                                <RowDefinition Height="27"/>
                            </Grid.RowDefinitions>
                            <Grid.ColumnDefinitions>
                                <ColumnDefinition Width="60"/>
                                <ColumnDefinition Width="5"/>
                                <ColumnDefinition Width="105"/>
                                <ColumnDefinition Width="35"/>
                                <ColumnDefinition Width="60"/>
                                <ColumnDefinition Width="36"/>
                            </Grid.ColumnDefinitions>
                            <Label Grid.Column="0" Grid.Row="0" FontSize="Medium" TextColor="White" Text="{Binding Year}" HorizontalTextAlignment="Center"/>
                            <Label Grid.Column="2" Grid.Row="0" FontSize="Medium" TextColor="White" Text="{Binding Name}" Grid.ColumnSpan="2"  HorizontalTextAlignment="Start"/>
                            <Switch x:Name="{Binding Id}" IsToggled="{Binding IsChecked, Mode=TwoWay}" Toggled="Handle_Toggled" Grid.Column="6" Grid.Row="0" />
                        </Grid>
                    </ViewCell.View>
                </ViewCell>
            </DataTemplate>
        </ListView.ItemTemplate>
    </ListView>

查看模型代码

    public AutoWithSwitch SelectedItem
    {
        get
        {
            return _selectedItem;
        }
        set
        {
            _selectedItem = value;

            if (_selectedItem == null)
                return;
            DisplayAlerts(value);
        }
    }

    public async void DisplayAlerts(AutoWithSwitch value)
    {           
        Application.Current.Properties["DeleteData"] = value;            
        DependencyService.Get<IMessage>().LongAlert("Stupid");            
    }

公共项目中定义的接口

public interface IMessage
{
    void ShowMsg(Mileage value);
    void LongAlert(string message);
    void ShortAlert(string message);
}

iOS 项目中用于显示警报的代码

    public void LongAlert(string message)
    {
        ShowAlert(message);
    }
    public void ShortAlert(string message)
    {
        ShowAlert(message);
    }

    void ShowAlert(string message)
    {
        UpdateCarsViewModel ucvm = new UpdateCarsViewModel();
        //alertDelay = NSTimer.CreateScheduledTimer(seconds, (obj) =>
        //{
        //    dismissMessage();
        //});
        alert = UIAlertController.Create(null, "Action", UIAlertControllerStyle.Alert);
        alert.AddAction(UIAlertAction.Create("Delete", UIAlertActionStyle.Default,UIAlertAction => ucvm.DeleteCar()));
        alert.AddAction(UIAlertAction.Create("Cancel", UIAlertActionStyle.Cancel, null));
        UIApplication.SharedApplication.KeyWindow.RootViewController.PresentViewController(alert, true, null);
    }

同样，这在模拟器中有效，但在 iPhone 上它完全没有任何作用。您能给我的任何帮助将不胜感激。非常感谢！

Answer 1

我终于使用推荐的 ItemSelected 让它工作了。这是有效的代码。

景色

<ListView x:Name="AutoView" ItemsSource="{Binding AutoData}" ItemSelected="Selected" Grid.Row="1" Grid.ColumnSpan="6" BackgroundColor="Purple">

View背后的代码

void Selected(object sender, SelectedItemChangedEventArgs e)
     {
         if (Convert.ToBoolean(Application.Current.Properties["FirstSelected"]))
         {
             Application.Current.Properties["FirstSelected"] = false;
             //Analytics.TrackEvent("UpdateCar.xaml.cs - Select top");
             var ucvm = new UpdateCarsViewModel((AutoWithSwitch)e.SelectedItem);
             //Analytics.TrackEvent("UpdateCar.xaml.cs - Select top2" + (AutoWithSwitch)e.SelectedItem);

             if (e.SelectedItem == null)
             {                    
                 return;
             }
                
             AutoView.SelectedItem = null;                
         }
     }

视图模型

 public UpdateCarsViewModel(AutoWithSwitch data)
     {
         StackTrace stackTrace = new StackTrace();
         // Get calling method name
         var methodName = stackTrace.GetFrame(1).GetMethod().Name;
         Analytics.TrackEvent("In UpdateCarsViewModel MethodName = " + methodName);
         if (methodName == "Selected")
         {
             DisplayAlerts(data);                
         }
     }

 public async void DisplayAlerts(AutoWithSwitch value)
     {           
         var answer = await (App.Current as App).MainPage.DisplayAlert("Action", "Delete", "Ok", "Cancel");
         if (answer)
             DeleteCar(value);
         else
             Application.Current.Properties["FirstSelected"] = true;            
     }

感谢大家的帮助

无论我用什么方式编码，都无法在 iPhone 上显示警报，我尝试了 4 种不同的方式

Cannot get Alerts to show on iPhone no matter what way I code it and I have tried 4 different ways

c#

ios

xamarin

xamarin.forms