Creating Dynamic TabbedPage using Prism Xamarin forms - mvvm

Question

I am using Prism with item source, Inside each tabbed page there is a Listview for which i am unable utilize "ItemTapped" event as an event to command Behaviour to trigger a command in viewmodel when an listview item is tapped, but there is no trigger in debug mode when i tap an list view item, Please help me understand why this is happening and is there any alternate way in which i can use command for this. Also when i checked The event is getting triggered in PrismTabbedPage1.xaml.cs but not in PrismTabbedPage1ViewModel.cs
Prism Xamarin forms
PrismTabbedPage1.Xaml
<?xml version="1.0" encoding="utf-8" ?>
<TabbedPage xmlns="http://xamarin.com/schemas/2014/forms" xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml" xmlns:prism="clr-namespace:Prism.Mvvm;assembly=Prism.Forms" xmlns:behaviors="clr-namespace:Prism.Behaviors;assembly=Prism.Forms" prism:ViewModelLocator.AutowireViewModel="True" x:Class="testapp.Views.PrismTabbedPage1" ItemsSource="{Binding countries}"> <TabbedPage.ItemTemplate>
<DataTemplate>
<ContentPage Title="{Binding CountryName}">
<ListView ItemsSource="{Binding Cities}">
<ListView.ItemTemplate>
<DataTemplate>
<ViewCell>
<Label Text="{Binding CityName}" TextColor="Black"/>
</ViewCell>
</DataTemplate>
</ListView.ItemTemplate>
<ListView.Behaviors>
<behaviors:EventToCommandBehavior EventName="ItemTapped" Command="{Binding ListItemTapped}" EventArgsParameterPath="Item"/>
</ListView.Behaviors> </ListView>
</ContentPage>
</DataTemplate>
</TabbedPage.ItemTemplate>
</TabbedPage>`
PrismTabbedPage1ViewModel.cs
using Prism.Mvvm;
using Prism.Navigation;
using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.Linq;
using testapp.Models;
namespace testapp.ViewModels
{
public class PrismTabbedPage1ViewModel : BindableBase
{
public ObservableCollection<Country> countries { get; set; }
public DelegateCommand<Country> ListItemTapped => new DelegateCommand<Country>(OnTapped);
private void OnTapped(Country obj)
{
//NavigationService.NavigateAsync("MainPage");
}
public PrismTabbedPage1ViewModel()
{
ObservableCollection<City> Cities1 = new ObservableCollection<City>()
{
new City(){ CityName = "City1" },new City(){ CityName = "City2" },new City(){ CityName = "City3" },
new City(){ CityName = "City4" },new City(){ CityName = "City5" },new City(){ CityName = "City6" },
new City(){ CityName = "City7" },new City(){ CityName = "City8" },new City(){ CityName = "City9" },
};
countries = new ObservableCollection<Country>()
{
new Country(){ CountryName = "Country 1", Cities = Cities1 },
new Country(){ CountryName = "Country 2", Cities = Cities1 },
new Country(){ CountryName = "Country 3", Cities = Cities1 },
};
}
}
}
Country.cs
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.Text;
namespace testapp.Models
{
public class Country
{
public string CountryName { get; set; }
public ObservableCollection Cities { get; set; }
}
public class City
{
public string CityName { get; set; }
}
}
In this code the listview command behaviour is not get triggered.

Answer 1

I'm not familiar with Prism but since your EventToCommand is inside a ListView, your default binding is the data passed by the listview, and not your ViewModel.
You could try something like this :
<behaviors:EventToCommandBehavior EventName="ItemTapped"
Command="{Binding Source={x:Reference this},Path=BindingContext.ListItemTapped}"
EventArgsParameterPath="{Binding .}"/>
And give a name to your page :
<TabbedPage .... x:Name="this">
So your binding inside your listview should effectively redirect to the command in your viewmodel.
I hope this helps.