EventHandler为空，因此无法使用Tapgesturerecognizer在MainPage命令上调用

using System.Windows.Input;
using Xamarin.Forms;

public class MainViewModel
{
    public ICommand TapCommand { get; }

    public MainViewModel()
    {
        TapCommand = new Command(OnTapped);
    }

    private void OnTapped()
    {
        // 处理点击事件
        Application.Current.MainPage.DisplayAlert("Tapped", "You tapped the label!", "OK");
    }
}

using Xamarin.Forms;

public partial class MainPage : ContentPage
{
    public MainPage()
    {
        InitializeComponent();
        BindingContext = new MainViewModel();
    }
}

<?xml version="1.0" encoding="utf-8" ?>
<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
             x:Class="YourNamespace.MainPage">

    <StackLayout>
        <Label Text="Tap me!"
               VerticalOptions="CenterAndExpand" 
               HorizontalOptions="CenterAndExpand">
            <Label.GestureRecognizers>
                <TapGestureRecognizer Command="{Binding TapCommand}" />
            </Label.GestureRecognizers>
        </Label>
    </StackLayout>

</ContentPage>