Show a refresh page IOS-Xamarin - ios

Question

For my ios application I need to handle those cases where the server returns an error, there are a couple of errors I am interested in handle, such as Not Found and Timed Out.
I'm developing with Xamarin and Windows Azure Mobile Services. So far, I know how to catch these exceptions, however, in case of an exception I would like to show a view that contains a refresh button, which the user can press in order to refresh (go to the server and see if there is new data, remove the refresh view, and display the new info).
this is how I'm capturing the exceptions thrown by the server:
public async RefreshAsync(){
try
{
var results = await DailyWorkoutTable.ToListAsync();
wod = results.FirstOrDefault();
SetupUI();
}
catch(Exception e)
{
var ex = e.GetBaseException() as MobileServiceInvalidOperationException;
if(ex.Response.StatusCode == 404)
{
//this is where I need to set up the refresh view and
//and add a UIButton to it
Console.WriteLine("Daily workout not found");
}
}
}
I don't know what's the right way to accomplish this. If I create a UIView and add a UIButton to it, with an event which calls RefreshAsync again, it will not work and is not the most elegant way to do it.
Is there another approach on this?? please help.

Answer 1

Here is an example you can use as a starting point:
/// <summary>
/// A class for performing Tasks and prompting the user to retry on failure
/// </summary>
public class RetryDialog
{
/// <summary>
/// Performs a task, then prompts the user to retry if it fails
/// </summary>
public void Perform(Func<Task> func)
{
func().ContinueWith(t =>
{
if (t.IsFaulted)
{
//TODO: you might want to log the error
ShowPopup().ContinueWith(task =>
{
if (task.IsCompleted)
Perform(func);
}, TaskScheduler.FromCurrentSynchronizationContext());
}
}, TaskScheduler.FromCurrentSynchronizationContext());
}
/// <summary>
/// Wraps a retry/cancel popup in a Task
/// </summary>
private Task ShowPopup()
{
var taskCompletionSource = new TaskCompletionSource<bool>();
var alertView = new UIAlertView("", "Something went wrong, retry?", null, "Ok", "Cancel");
alertView.Dismissed += (sender, e) => {
if (e.ButtonIndex == 0)
taskCompletionSource.SetResult(true);
else
taskCompletionSource.SetCanceled();
};
alertView.Show();
return taskCompletionSource.Task;
}
}
To use it:
var retryDialog = new RetryDialog();
retryDialog.Perform(() => DoSomethingThatReturnsTask());
This example is prior to async/await support, but you can refactor it if desired.
You might also consider making Perform() return a Task and become async -- depending on your use case.