Unable to show Xamarin Forms MVVM binding result in listview - mvvm

Question

I am trying to implement MVVM approach in my xamarin forms application. During the implementations, I have hit a road block. I am unable to populate the list view with the data that i recieve from the server. I am unable to identify the binding issue.
Please let me know where is my mistake? What am I missing?
View Code
<?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="Test.Views.SubtaskPage"
Title="Select Subtask"
xmlns:viewModels="clr-namespace:Test.ViewModels; assembly=Test">
<ContentPage.BindingContext>
<viewModels:SubtaskPageViewModel/>
</ContentPage.BindingContext>
<ContentPage.ToolbarItems>
<ToolbarItem x:Name="tbiAddSubtask" Text="Add Subtask" Clicked="tbiAddSubtask_Clicked"/>
</ContentPage.ToolbarItems>
<StackLayout Orientation="Vertical" Padding="10">
<ListView x:Name="lstSubtasks" ItemSelected="lstSubtasks_ItemSelected" IsPullToRefreshEnabled="True" RefreshCommand="{Binding RefreshCommand}" IsRefreshing="{Binding IsBusy}" ItemsSource="{Binding SubtaskList}}">
<ListView.ItemTemplate>
<DataTemplate>
<ViewCell>
<ViewCell.ContextActions>
<MenuItem x:Name="menuAddTimeSpent" Clicked="menuItem_Clicked" CommandParameter="{Binding Ticket}" Text="Menu" />
</ViewCell.ContextActions>
<StackLayout Padding="20,0,0,0" HorizontalOptions="StartAndExpand" Orientation="Horizontal">
<Label Text="{Binding Subject}" VerticalTextAlignment="Center" />
</StackLayout>
</ViewCell>
</DataTemplate>
</ListView.ItemTemplate>
</ListView>
</StackLayout>
</ContentPage>
Response Class Code
public class SubtasksResponse
{
public int Status { get; set; }
public string Message { get; set; }
public List<Ticket> Subtasks { get; set; }
}
View Model Code
public class SubtaskPageViewModel : INotifyPropertyChanged
{
private SubtasksResponse _subtaskList;
public SubtasksResponse SubtaskList
{
get { return _subtaskList; }
set
{
_subtaskList = value;
OnPropertyChanged(nameof(SubtaskList));
}
}
private Command _refreshCommand;
public Command RefreshCommand
{
get
{
return _refreshCommand;
}
}
bool _isBusy;
public bool IsBusy
{
get { return _isBusy; }
set
{
_isBusy = value;
OnPropertyChanged(nameof(IsBusy));
}
}
public SubtaskPageViewModel()
{
_refreshCommand = new Command(RefreshList);
}
async void RefreshList()
{
SubtaskList = await PopulateSubtaskList();
}
async Task<SubtasksResponse> PopulateSubtaskList()
{
RestService rs = new RestService();
IsBusy = true;
IsBusy = false;
var subtaskList = new SubtasksResponse();
subtaskList = await rs.GetSubtasksAsync(Convert.ToInt32(Application.Current.Properties["UserId"]));
return subtaskList;
}
public event PropertyChangedEventHandler PropertyChanged;
protected virtual void OnPropertyChanged(string propertyName)
{
if (PropertyChanged != null)
{
PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
}
}
}

Answer 1

For starters we see you are binding the ListView to ItemsSource="{Binding SubtaskList} - when we then look at the ViewModel it seems that SubtaskList is of type SubtasksResponse, that type only has 3 properties.
But the item template inside your ListView is not using any of those 3 properties... it's using Ticket and Subject.
Are this properties of the class Subtasks? If so you need to bind the ListView directly to the List property for it to pick up the items in that collection.