creating a sdk for xamarin forms

Question

All I have to do is create a library for Xamarin forms applications based on my native code(kotlin and swift). I created a multiplatform library and added platform-specific projects and a shared project. I also have two binding projects (one for Android and the other for iOS).

I'm trying to set up a DependencyService to invoke platform-specific code in a Multiplatform project so that I can use my library in an XF project.

When calling a DependencyService.Get<IService>() in the shared project I get null. (null reference exception)

I tried to register it like this: [assembly: Dependency (type (service))] - on top of the namespace declaration inside the iOS and Android projects, which I'm going to use in the XF project. I also tried to register the service in AppDelegate, but the error doesn't go away.

Here is an example of code that doesn't work: Interface in my shared project:

public interface IDevice
    {
        string GetInfo();
    }

This is an implementation of interface on the iOS:

[assembly: Xamarin.Forms.Dependency(typeof([path to namespace].DeviceService))]
namespace [path to namespace]
{
    public class DeviceService : IDevice
    {
        public string GetInfo()
        {
            return "some string";
        }
    }

}

A class with a method in a shared project that I will call from my XF project:

public class GrowDevice
    {
        static IDevice device;

        public GrowDevice()
        {
            DependencyService.Get<IDevice>();
        }

        public string GetInfo()
        {
            return device.GetInfo();
        }
    }

This is a code example of how I will call the GetInfo() method which is in the multiplatform library in a shared project, from my xamarin.froms project:

public ICommand GetDeviceInfoCommand => new Command(async () => { await GetInfo(); });

       
        private async Task GetInfo()
        {
            var grow = new [path to class].GrowDevice();
            Device = grow.GetInfo();
        }

How can I call platform specific code in the iOS project from the Shared project with DependencyService? Or maybe there is some other way?

Answer 1

You should assignment the result of the DependencyService.Get() to the staic variable which you have declared.

public class GrowDevice
{
    static IDevice device;

    public GrowDevice()
    {
       device = DependencyService.Get<IDevice>();
    }

    public string GetInfo()
    {
        return device.GetInfo();
    }
}