i am trying to retrive a unique id of mobile using mobile xamarin application i am using in

MainActivity.Cs

public class AndroidDevice : IDevice
    {

        public string GetIdentifier()
        {
            var context = Android.App.Application.Context;
            return Android.Provider.Settings.Secure.GetString(context.ContentResolver, Android.Provider.Settings.Secure.AndroidId);
        }

}

and i created a Interface in shared project as

 public interface IDevice
    {
        string GetIdentifier();
    }

i called the function in shaed project as

string deviceIdentifier = DependencyService.Get<IDevice>().GetIdentifier();

i alawys get

System.NullReferenceException: 'Object reference not set to an instance of an object.'

CodePudding user response：

You need to add Dependency attribute to the assembly namespace where the class that implements the interface is declared.

Eg.

[assembly: Dependency(typeof(DroidImplementation))]
namespace MyApp.Droid.Implementation
{
    public class DroidImplementation : IMyInterface
    {
       // your class implementation here
    }
}

I wouldn't add the class to the MainActivity.cs but create a separate namespace for that.