How to get a Layout object (such as Grid or StackPanel) from LayoutPanel object?

dg2k 1,391 Reputation points
2022-09-05T14:21:50.677+00:00

I am migrating Xamarin code to .NET MAUI. I am using PlatformEffect to capture the RightTapped event for WinUI.

The equivalent is done for other platforms such as Android by using the SwipeView Control.

Shown below are partial XAML code and complete RightTappedEffect handler classes with a bit of code missing in the event handler at the end (i.e., the code I couldn't figure out). The Effect is registered in the MauiProgram.cs (using #if WINDOWS conditional) as: effects.Add<RightTappedEffect, RightTappedPlatformEffect>(); Everything seem to work except I couldn't determine the Grid Control that generates the RightTapped event from the very event handler.

The RightTapped event handler returns LayoutPanel as sender event object. In the case of Xamarin, LayoutRenderer is returned by sender object and Grid is simply Element property of LayoutRenderer.

My question is: How do I get the Grid Control from the LayoutPanel object returned by the RightTapped event handler in MAUI, as shown at the end?

Partial XAML Code:

 <ContentPage  
    x:Class="MauiTest.Views.MainPage"  
    xmlns="http://schemas.microsoft.com/dotnet/2021/maui"  
    xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"  
    xmlns:e="clr-namespace:MauiTest.Effects"  
   xmlns:vm="clr-namespace:MauiTest.ViewModels"  
  
   . . .  
  
    <CollectionView.GroupHeaderTemplate>  
        <DataTemplate>  
            <Grid  
                Margin="0"  
                Padding="0"  
                e:RightTappedEffect.Command="{Binding RightTappedCommand, Source={RelativeSource AncestorType={x:Type vm:PageViewModel}}}">  
                <Grid.Effects>  
                    <e:RightTappedEffect />  
                </Grid.Effects>  
  
   . . .  
  
</ContentPage>  

Platform Effect Handler Classes:

     public  class RightTappedEffect: RoutingEffect  
      {  
            public RightTappedEffect() { }  
      
            public static readonly BindableProperty CommandProperty = BindableProperty.CreateAttached("Command", typeof(ICommand), typeof(TapAndHoldEffect), null);  
            public static ICommand GetCommand(BindableObject view) => (ICommand)view.GetValue(CommandProperty);  
            public static void SetCommand(BindableObject view, ICommand value) => view.SetValue(CommandProperty, value);  
     }  
  
  
public class RightTappedPlatformEffect : PlatformEffect  
{  
    public RightTappedPlatformEffect () { }  
  
    protected override void OnAttached()  
    {  
        if (this.Container is UIElement uiElement)  
        {  
            uiElement.RightTapped += UIElement_RightTapped;  
        }  
    }  
  
    protected override void OnDetached()  
    {  
        if (this.Container is UIElement uiElement)  
        {  
            uiElement.RightTapped -= UIElement_RightTapped;  
        }  
    }  
  
  
    private void UIElement_RightTapped(object sender, RightTappedRoutedEventArgs e)  
    {  
        if (sender is not LayoutPanel layoutPanel) return;  
  
        // debug hits this point upon right-click!  
        // how to get a Grid object from the layoutPanel ?????????????  
    }  
}  
.NET MAUI
.NET MAUI
A Microsoft open-source framework for building native device applications spanning mobile, tablet, and desktop.
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  1. Yonglun Liu (Shanghai Wicresoft Co,.Ltd.) 37,581 Reputation points Microsoft Vendor
    2022-09-06T07:12:15.563+00:00

    Hello,

    As a matter of fact, the layoutPanel is your Grid object.

    You could try to the following steps to confirm it.

    Step1: Add a Label into Grid: <Label Text="111"/>

    Step2: In the UIElement_RightTapped method, you could add the following code to change the Text value of the Label:

       var ch = layoutPanel.Children;  
       foreach(var c in ch)  
       {  
           var test = c as TextBlock;  
           test.Text = "123";  
       }  
    

    Best Regards,

    Alec Liu.


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