How to apply alert dialog after response

Question

public async Task<ObservableCollection<CustomerModel>> GetCustomer(string customerNumber, string department)
        {
            try
            {
                progressBar.Visibility = ViewStates.Visible;
                progressBar.Progress = 0;
                listofItems = new ObservableCollection<CustomerModel>();
                string url = _client.BaseAddress + "/getcustomers(Number='" + customerNumber + "',department='" +
                             department + "')";
                var response = await _client.GetAsync(url);
                if (response.IsSuccessStatusCode)
                {
                    progressBar.Visibility = ViewStates.Invisible;
                    progressBar.Progress = 100;
                    string returnjson = await response.Content.ReadAsStringAsync();
                    ReplyCustomerModel replyCustomerModel =
                        JsonConvert.DeserializeObject<ReplyCustomerModel>(returnjson);
                    if (replyCustomerModel != null)
                    {
                        listofItems = replyCustomerModel.Customers;
                    }

                }
                else
                {

                    AlertDialog.Builder alertDiag = new AlertDialog.Builder();
                    alertDiag.SetTitle("Butikscanner App");
                    alertDiag.SetMessage("User Does not exist");
                    alertDiag.SetPositiveButton("OK",
                        (senderAlert, args) => { });
                    alertDiag.SetNegativeButton("Cancel", (senderAlert, args) => { alertDiag.Dispose(); });
                    Dialog diag = alertDiag.Create();
                    diag.Show();


                }

                return listofItems;
            }
            catch (Exception ex)
            {
                Console.WriteLine(ex);
                throw;
            }
        }

Actually that is what i am doing if my response is false i am trying to show alert dialog that user does not exist I am working my project in MVVM light

Actually that is what i am doing if my response is false i am trying to show alert dialog that user does not exist I am working my project in MVVM light

Actually that is what i am doing if my response is false i am trying to show alert dialog that user does not exist I am working my project in MVVM light

Answer 1

Usually, API calls are made in a background thread using async-await if that is the case with you as well then I would suggest that you do is call the dialog's show method on the UIThread. For this, you will need an activity context i.e. An activity's reference.

There are two way for you to do it either directly call this method as an action something like this:

private void ShowDialog()
{                    
AlertDialog.Builder alertDiag = new AlertDialog.Builder();
alertDiag.SetTitle("Butikscanner App");
alertDiag.SetMessage("User Does not exist");
alertDiag.SetPositiveButton("OK",(senderAlert, args) => {  });
alertDiag.SetNegativeButton("Cancel", (senderAlert, args) => { alertDiag.Dispose(); });
Dialog diag = alertDiag.Create();
diag.Show();    
}

assuming above is how your method is defined you can run it on UI thread like:

activity.RunOnUIThread(ShowDialog);

But in your scenario, I do not personally think that this is a smart thing to do because the only line of code that is supposed to be on UIThread(at least i think so) is the dialog.Show();

What you should do rather would be use a lamba expression for a anonymous method something like:

private void ShowDialog(Activity activity)
{                    
AlertDialog.Builder alertDiag = new AlertDialog.Builder();
alertDiag.SetTitle("Butikscanner App");
alertDiag.SetMessage("User Does not exist");
alertDiag.SetPositiveButton("OK",(senderAlert, args) => {  });
alertDiag.SetNegativeButton("Cancel", (senderAlert, args) => { alertDiag.Dispose(); });
Dialog diag = alertDiag.Create();
activity.RunOnUIThread(()=>
 {diag.Show();});
}