public ListViewModel()
{
this.Source = new ListViewLoadOnDemandCollection((cancelationToken) =>
{
List <string> result = new List <string>();
try
{
//simulates connection latency
Task.Delay(4000, cancelationToken).Wait();
this.lodTriggerCount++;
foreach (string item in Enum.GetNames(typeof(DayOfWeek)))
{
result.Add(string.Format("LOD: {0} - {1}", lodTriggerCount, item));
}
return(result);
}
catch (Exception ex)
{
//exception is thrown when the task is canceled. Returning null does not affect the ItemsSource.
return(null);
}
});
for (int i = 0; i < 14; i++)
{
Source.Add(string.Format("Item {0}", i));
}
}
public CharactersViewModel()
{
Title = "Characters";
Characters = new ListViewLoadOnDemandCollection((token) =>
{
try
{
// Since the caller run this delegate in a separate task, we can use .Result here safely and it wont block UI thread
var apiResult = ApiService.GetCharactersAsync(CurrentCharactersCount, 50).Result;
if (apiResult != null)
{
// We need to marshal to UI thread to update these properties
Device.BeginInvokeOnMainThread(() =>
{
CurrentCharactersCount = apiResult.Offset + apiResult.NumberOfPageResults;
TotalCharactersCount = apiResult.NumberOfTotalResults;
});
return(apiResult.Results);
}
}
catch (Exception exception)
{
Debug.WriteLine($"FetchMoreCharacters Exception: {exception}");
}
return(null);
});
}
