How to update list view from another class in Xamarin forms? - class

Question

I have created a list view in one class and called delete method from another class. Listview getting call but not updating list view if i call from another class. But its getting update when i call inside the same class. How to solve this issue?
namespace New
{
public partial class WishesPage : ContentPage
{
ListView listView = new ListView();
public WishesPage()
{
InitializeComponent();
var arr = JToken.Parse(ids);
foreach (var ite in arr.Children())
{
var itemProperties = ite.Children<JProperty>();
string contactElement = itemProperties.FirstOrDefault(x => x.Name == "contact").Value.ToString();
sample.Add(contactElement);
}
listView.ItemTemplate = new DataTemplate(typeof(CustomListCell));
listView.ItemsSource = sample;
Content = new StackLayout
{
Children =
{
listView,
}
};
}
public async Task delete(string wishid)
{
indicator.IsRunning = true;
var client = new HttpClient();
client.BaseAddress = new Uri("http:……”);
if (response == "success")
{
listView.ItemsSource = null;
listView.ItemsSource = sample;
}
}
}
public class CustomListCell : ViewCell
{
public CustomListCell()
{
wishIdLabel.SetBinding(Label.TextProperty, new Binding("contact"));
horizontalLayout.Children.Add(wishIdLabel);
var deleteAction = new MenuItem { Text = "Delete", IsDestructive = true };
deleteAction.Clicked += async (sender, e) =>
{
WishesPage wishes = new WishesPage();
wishes.delete(wishId);
};
ContextActions.Add(deleteAction);
}
}
}

Answer 1

I have updated this repo that explain how to use Commands inside a ViewCell.
In your case, you should move the construction of ViewCell inside the ContentPage. Something like
lv.ItemTemplate = new DataTemplate(() =>
{
StackLayout slView = new StackLayout();
Label lDesc = new Label();
lDesc.SetBinding(Label.TextProperty, "Description", stringFormat: "DESCRIPTION: {0}");
var deleteAction = new MenuItem { Text = "Delete", IsDestructive = true }; // red background
deleteAction.SetBinding(MenuItem.CommandProperty, new Binding("BindingContext.TrashCommand", source: this));
deleteAction.SetBinding(MenuItem.CommandParameterProperty, ".");
slView.Children.Add(lDesc);
ViewCell vc = new ViewCell() {View = slView };
vc.ContextActions.Add(deleteAction);
return vc;
}
Now, when you longpress the row, a ContextAction "Delete" appears and a TrashCommand in your ViewModel is executed (you should use MVVM...), a "these" parameter is passed (the selected obj) so you can delete it from the List
this.TrashCommand = new Command(async (object obj) => {
try
{
if (_isTapped)
return;
if (obj != null)
System.Diagnostics.Debug.WriteLine("Obj is not null");
else
System.Diagnostics.Debug.WriteLine("Obj IS null");
_isTapped = true;
var ret = await Application.Current.MainPage.DisplayAlert("Attention", "Delete this row?", "Yes", "No");
if (ret)
{
// List is your "sample" list... Removing the obj, is it reflected to ListView if you use ObservableCollection instead of List
List.Remove((Model)obj);
Count = List.Count;
}
_isTapped = false;
}
catch (Exception ex) {
_isTapped = false;
await Application.Current.MainPage.DisplayAlert("Attention", ex.Message, "Ok");
}
});
}