Requesting Android permissions in a class (Xamarin) - xamarin

Question

I'm trying to request a permission at runtime for my app. I use a service provider to talk between the portable class and Android.
I start by calling this code on button press in the PCL:
using (new Busy(this))
{
var locationHelper = scope.Resolve<ILocationHelper>();
locationHelper.GetLocation(this);
}
This calls my Android level service:
public class AndroidLocationHelper : ILocationHelper, ILocationListener
{
readonly string[] PermissionsLocation =
{
Manifest.Permission.AccessCoarseLocation
};
const int RequestLocationId = 0;
public void GetLocation(SearchViewModel viewModel)
{
try
{
const string permission = Manifest.Permission.AccessCoarseLocation;
if (((int)Build.VERSION.SdkInt < 23) || (CheckSelfPermission(permission) == Permission.Granted))
{
}
else
RequestPermissions(PermissionsLocation, RequestLocationId);
}
catch (Exception ex)
{
Debug.WriteLine("Error while getting Location service");
Debug.WriteLine(ex.Message);
Messaging.AlertUser("There was an error with determining your location");
}
}
However, I get two errors on CheckSelfPermission and RequestPermissions. These two methods are only available to activities. The code works fine in MainActivity; however, I want to ask for permissions when the user hits a button, not in OnCreate or OnResume, etc.
Thanks for any help.

Answer 1

In your Android project, You can use this and use the Dependency Service to call it in Xamarin.Forms PCL project later:
var thisActivity = Forms.Context as Activity;
ActivityCompat.RequestPermissions(thisActivity, new string[] {
Manifest.Permission.AccessFineLocation }, 1);
ActivityCompat.RequestPermissions(thisActivity,
new String[] { Manifest.Permission.AccessFineLocation },
1);

Answer 2

You can try with ContextCompat.CheckSelfPermission, passing the application context, like this:
ContextCompat.CheckSelfPermission(Android.App.Application.Context, permission)
Update
In case of ActivityCompat.RequestPermissions, which requires an activity reference, you can keep track of the current activity. There is a very handy lib for that, called "CurrentActivityPlugin". You can find at https://github.com/jamesmontemagno/CurrentActivityPlugin

Answer 3

Rafael came up with a solution but I found another option that is a lot less effort just using MessagingCenter. In the MainActivity's OnCreate add a receiver that runs all the location code, that way you have access to all of the activities methods (and there are a bunch of tutorials on doing location services in MainActivity). Then add the Send inside of your service (the class).

Answer 4

To expound Rafael Steil's answer, I tried the suggested CurrentActivityPlugin and it worked on me. In my case I am trying to execute a voice call which needs CALL_PHONE permission. Here is the code snippet in your case: I used the ContextCompat & ActivityCompat so that I don't need to check the VERSION.SdkInt
using Plugin.CurrentActivity;
public void GetLocation(SearchViewModel viewModel){
var context = CrossCurrentActivity.Current.AppContext;
var activity = CrossCurrentActivity.Current.Activity;
int YOUR_ASSIGNED_REQUEST_CODE = 9;
if (ContextCompat.CheckSelfPermission(context, Manifest.Permission.AccessCoarseLocation) == (int)Android.Content.PM.Permission.Granted)
{
//Permission is granted, execute stuff
}
else
{
ActivityCompat.RequestPermissions(activity, new string[] { Manifest.Permission.AccessCoarseLocation }, YOUR_ASSIGNED_REQUEST_CODE);
}
}

Answer 5

It's dead simple
public bool CheckPermission()
{
const string permission = Manifest.Permission.ReceiveSms;
return ContextCompat.CheckSelfPermission(Forms.Context, permission) == (int) Permission.Granted;
}