I have been trying to bind my ListView to my View model. The view model successfully retrieves 5 records from the database and the Listview seems to display 5 blank rows, however it is not showing binding for each field within each row.
I have spent a couple of days searching internet but I don't seem to be doing anything different. I was using master detail pages so I thought that it may be the issue so I set my Events page as first navigation page without master/detail scenario but to no avail. Please note that I am using Portable Ninject for my dependencies/IoC.
My App.Xamal.cs is is as follows:
public App (params INinjectModule[] platformModules)
{
InitializeComponent();
var eventsPage = new NavigationPage(new EventsPage());
//Register core services
Kernel = new StandardKernel(new MyAppCoreModule(), new MyAppNavModule(eventsPage.Navigation));
//Register platform specific services
Kernel.Load(platformModules);
//Get the MainViewModel from the IoC
eventsPage.BindingContext = Kernel.Get<EventsViewModel>();
((BaseViewModel)(eventsPage.BindingContext)).Init();
MainPage = eventsPage;
}
My EventsPage.Xaml is provided below:
<?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="MyApp.Views.EventsPage"
Title="Events">
<ContentPage.Content>
<ListView x:Name="Events" ItemsSource="{Binding Events}" >
<ListView.ItemTemplate>
<DataTemplate>
<ViewCell>
<Label Text="{Binding EventID}" BackgroundColor="Red" TextColor="White"
FontAttributes="Bold" />
</ViewCell>
</DataTemplate>
</ListView.ItemTemplate>
</ListView>
</ContentPage.Content>
</ContentPage>
My EventsPage.xaml.cs is provided below:
namespace MyApp.Views
{
[XamlCompilation(XamlCompilationOptions.Compile)]
public partial class EventsPage : ContentPage, IBaseViewFor<EventsViewModel>
{
public EventsPage ()
{
InitializeComponent ();
}
EventsViewModel _vm;
public EventsViewModel ViewModel
{
get => _vm;
set
{
_vm = value;
BindingContext = _vm;
}
}
}
}
My EventsViewModel is as follows, it successfully retrieves 5 records and OnPropertyChanged is fired for Events property:
namespace MyApp.ViewModels
{
public class EventsViewModel : BaseViewModel, IBaseViewModel
{
ObservableCollection<Event> _events;
readonly IEventDataService _eventDataService;
public ObservableCollection<Event> Events
{
get { return _events; }
set
{
_events = value;
OnPropertyChanged();
}
}
public EventsViewModel(INavService navService, IEventDataService eventDataService) : base(navService)
{
_eventDataService = eventDataService;
Events = new ObservableCollection<Event>();
}
public override async Task Init()
{
LoadEntries();
}
async void LoadEntries()
{
try
{
var events = await _eventDataService.GetEventsAsync();
Events = new ObservableCollection<Event>(events);
}
finally
{
}
}
}
}
My BaseViewModel is as follows:
namespace MyApp.ViewModels
{
public abstract class BaseViewModel : INotifyPropertyChanged
{
protected INavService NavService { get; private set; }
protected BaseViewModel(INavService navService)
{
NavService = navService;
}
bool _isBusy;
public bool IsBusy
{
get
{
return _isBusy;
}
set
{
_isBusy = value;
OnPropertyChanged();
OnIsBusyChanged();
}
}
protected virtual void OnIsBusyChanged()
{
}
public abstract Task Init();
public event PropertyChangedEventHandler PropertyChanged;
protected virtual void OnPropertyChanged([CallerMemberName] string propertyName = null)
{
PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
}
}
// Secod BaseViewModel abstract base class with a generic type that will be used to pass strongly typed parameters to the Init method
public abstract class BaseViewModel<TParameter> : BaseViewModel
{
protected BaseViewModel(INavService navService) : base(navService)
{
}
public override async Task Init()
{
await Init(default(TParameter));
}
public abstract Task Init(TParameter parameter);
}
}
IBaseViewModel is just a blank interface:
public interface IBaseViewModel
{
}
IBaseViewFor is given below:
namespace MyApp.ViewModels
{
public interface IBaseViewFor
{
}
public interface IBaseViewFor<T> : IBaseViewFor where T : IBaseViewModel
{
T ViewModel { get; set; }
}
}
My Event model is as follows:
namespace MyApp.Models
{
public class Event
{
public int EventID;
}
}
Finally, the image of the output, as you can see that 5 rows are created with red background but EventID is not binding in each row. I have checked the data and EventID is returned. I have even tried to manually add records into Events list but to no avail, see the manual code and image below:
async void LoadEntries()
{
try
{
Events.Add((new Event() { EventID = 1 }));
Events.Add((new Event() { EventID = 2 }));
Events.Add((new Event() { EventID = 3 }));
Events.Add((new Event() { EventID = 4 }));
Events.Add((new Event() { EventID = 5 }));
}
finally
{
}
}
I have spent a lot of time on it but unable to find a reason for this anomaly, can someone please cast a fresh eye and provide help!?
