I’m a developing an App for a Touch Panel.
I have encountered a problem with passing GotFocus data to my ViewModel. My button needs to know which text box is currently selected – it will change a given string in ViewModel based on the focus. I’m using the Community MVVM Toolkit.

Here is my User Control:

<UserControl xmlns="https://github.com/avaloniaui"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
             xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
             xmlns:vm="using:TouchPanel.ViewModels"
             xmlns:views="clr-namespace:TouchPanel.Views"
             mc:Ignorable="d" d:DesignWidth="1024" d:DesignHeight="600"
             x:Class="TouchPanel.Views.PickUpParcelView"
             x:DataType="vm:PickUpParcelViewModel">
    <Design.DataContext>
        <vm:PickUpParcelViewModel/>
    </Design.DataContext>
    <Grid>
        <Grid.ColumnDefinitions>
            <ColumnDefinition Width="512" />
            <ColumnDefinition Width="512" />
        </Grid.ColumnDefinitions>
        <StackPanel Grid.Column="0" VerticalAlignment="Center" Spacing="10" Margin="50">
            <TextBlock> Enter your phone number</TextBlock>
            <TextBox 
                Name="TextBoxPhoneNumber"
                Watermark="Ex. +00 123 456 789"
                Text="{Binding PhoneNumber}">
            </TextBox>
            <TextBlock> Enter your pick up code</TextBlock>
            <TextBox
                Name="TextBoxPickUpCode"
                Watermark="Ex. 42069"
                Text="{Binding PickUpCode}"
                GotFocus="TextBox_GotFocus"
                LostFocus="TextBox_LostFocus">
            </TextBox>
        </StackPanel>
        <StackPanel
            Grid.Column="1"
            Background="CadetBlue">
            <Button
                Command="{Binding AddLetterA}">
                Add Letter A
            </Button>
        </StackPanel>
    </Grid>
</UserControl>

The UserControl.axaml.cs

using Avalonia;
using Avalonia.Controls;
using Avalonia.Input;
using Avalonia.Interactivity;
using Avalonia.Markup.Xaml;
using System;
using System.Diagnostics;
using TouchPanel.ViewModels;
namespace TouchPanel.Views;

public partial class PickUpParcelView : UserControl
{
    bool gotFocus = false;
    public TextBox selectedTextBox; // i want to pass this to my viewmodel to modify
    public PickUpParcelView()
    {
        InitializeComponent();
    }
    public void TextBox_GotFocus(object source, GotFocusEventArgs args)
    {
        Debug.WriteLine("Got Focus");
        selectedTextBox = (TextBox)source;
        gotFocus = true;
    }
    public void TextBox_LostFocus(object source, RoutedEventArgs args)
    {
        Debug.WriteLine("LostFocus");
        gotFocus = false; 
    }
}

The ViewModel

using Avalonia.Controls;
using Avalonia.Input;
using Avalonia.Interactivity;
using CommunityToolkit.Mvvm.ComponentModel;
using CommunityToolkit.Mvvm.Input;
using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace TouchPanel.ViewModels
{
    public partial class PickUpParcelViewModel : ViewModelBase
    {
        [ObservableProperty]
        public string? _pickUpCode = string.Empty;

        [ObservableProperty]
        public string? _phoneNumber = string.Empty;

        [RelayCommand]
        public void AddLetterA()
        {
            PickUpCode += "A";
        }
    }
}

I tried looking it up for hour but to no avail, I could not find a suitable solution to my problem.
The tutorials and samples don’t seem to have a good solution either.