Freezing on permission request Xamarin.Forms - xamarin

Question

I want to get a user's position, and therefore I'm using James Montemagno's Geolocator Plugin for Xamarin. The author uses this code in the code-behind.cs file; I extracted it to a static class:
public static class GeoService
{
public static Position savedPosition;
public static async Task<Position> GetPosition()
{
var lastknown = await ExecuteLastKnownPosition();
if(lastknown == null)
{
var current = await ExecuteGPSPosition();
if(current != null)
{
return current;
}
else
{
return null;
}
}
return lastknown;
}
private static async Task<Position> ExecuteLastKnownPosition()
{
try
{
var hasPermission = await Utils.CheckPermissions(Permission.Location);
if (!hasPermission)
return null;
var locator = CrossGeolocator.Current;
locator.DesiredAccuracy = 50;
//Progress Ring einfügen
var position = await locator.GetLastKnownLocationAsync();
if (position == null)
{
//Benachrichtigung über null lastknownLocation
//Aufrufen der CurrentPosition Methode
return null;
}
savedPosition = position;
return position;
}
catch (Exception ex)
{
Debug.WriteLine(ex);
await Application.Current.MainPage.DisplayAlert("Uh oh", "Something went wrong, but don't worry we captured for analysis! Thanks.", "OK");
return null;
}
finally
{
//Freigabe der Buttons und Bools
}
}
private static async Task<Position> ExecuteGPSPosition()
{
try
{
var hasPermission = await Utils.CheckPermissions(Permission.Location);
if (!hasPermission)
return null;
var locator = CrossGeolocator.Current;
locator.DesiredAccuracy = 100;
//WarteText/Symbol
var position = await locator.GetPositionAsync(TimeSpan.FromSeconds(15));
if (position == null)
{
//Warnung, dass kein GPS vorhanden ist
return null;
}
savedPosition = position;
return position;
}
catch (Exception ex)
{
await Application.Current.MainPage.DisplayAlert("Uh oh", "Something went wrong, but don't worry we captured for analysis! Thanks.", "OK");
return null;
}
finally
{
//Zurücksetzen von Buttons und Lademodus beenden
}
}
public static async Task<Address> ExecuteTrackingAdress(Position currentPosition)
{
try
{
//if (savedPosition == null)
// return null;
var hasPermission = await Utils.CheckPermissions(Permission.Location);
if (!hasPermission)
return null;
string mapkey = "Ajbb9XXXXXXatUzUg1w9BSXXXXXVUAEuF4P-TSXJpnvl5OpXXXXXXXXX";
var locator = CrossGeolocator.Current;
var addresses = await locator.GetAddressesForPositionAsync(currentPosition, mapkey);
var address = addresses.FirstOrDefault();
if (address == null)
{
Debug.WriteLine("Keine Adresse vorhanden");
}
return address;
}
catch (Exception ex)
{
await Application.Current.MainPage.DisplayAlert("Uh oh", "Something went wrong, but don't worry we captured for analysis! Thanks.", "OK");
return null;
}
finally
{
}
}
}
Now I got a ContentPage, and when I go to that page (PushModalAsync) the constructor in the view model calls the GetPosition() method. There's a permission Task and whenever the Task is running, UWP offers me to prompt the location permission.
Unfortunately, from this point on the app is freezing. I can't choose Yes/No, and there's no way of interaction.
I tried to call the methods async, with Task.WhenAll() and so on, but it freezes every time.
This was the last code I wrote in my view model
private async void ExecuteGetPosition()
{
IsBusy = true;
await Task.Yield();
var positiontask = GeoService.GetPosition();
var addresstask = GeoService.ExecuteTrackingAdress(positiontask.Result);
await Task.WhenAll(positiontask, addresstask);
CurrentPosition = positiontask.Result;
CurrentAddress = addresstask.Result;
OnPropertyChanged("CurrentAddressView");
IsBusy = false;
}
I'm assuming that the XAML ContentPage isn't already loaded correctly, and so the prompting-window slips "behind" the MainWindow or something.
Please could you give me an idea for a workaround to handle this?
Edit:
Adding these lines to my App.xaml.cs OnStart()-Method brought the solution. Windows is now calling for permission OnStart, Android asks for permission on gps-request...crazy:
var permission = await CrossPermissions.Current.CheckPermissionStatusAsync(Permission.Location);

Answer 1

Are you running on iOS? If so, look at the simulator's console log to see if there is a privacy error. I am guessing it has to do with the privacy declarations required to be in the info.plist when requesting location permissions.
Check out all of the required privacy declarations listed here.
They include (check out the link for info on when to add each one):
<key>NSLocationWhenInUseUsageDescription</key>
<string>This app needs access location when open.</string>
<key>NSLocationAlwaysUsageDescription</key>
<string>This app needs access location when in the background.</string>
<key>NSLocationAlwaysAndWhenInUseUsageDescription</key>
<string>This app needs access location when open and in the background.</string>