MAUI: DependencyService.Get() return null

Question

I'm trying to migrate from Xamarin to MAUI.

The following code woked perfectly.

Xamarin project:

DependencyService.Get<IMyService>().Test();

Android:

[assembly: Dependency(typeof(MyService))]
namespace MyProject.Android
{
    public class MyService: IMyService
    {
        public void Test(){ 
            ////
        }
    }
}

And so on and so forth for IOS and Windows.

But MAUI's DependencyService.Get always return null. I cannot find what new changes have to be made. Reworking all code based on DependencyService in my main project would be painful.

What changes should be made in that case?

score 5 · Accepted Answer · edited Nov 03 '22 at 08:51

You don't have the concept of Platform dependency services in MAUI you can either use Conditional compilation or Partial classes to do what you need to do.

So if you check the Microsoft blog here: https://learn.microsoft.com/en-us/dotnet/maui/platform-integration/invoke-platform-code it shows you how you can use both these ways to invoke platform code.

So get the Orientation through conditional compilation:

#if ANDROID
using Android.Content;
using Android.Views;
using Android.Runtime;
#elif IOS
using UIKit;
#endif

using InvokePlatformCodeDemos.Services;

namespace InvokePlatformCodeDemos.Services.ConditionalCompilation
{
    public class DeviceOrientationService
    {
        public DeviceOrientation GetOrientation()
        {
#if ANDROID
            IWindowManager windowManager = Android.App.Application.Context.GetSystemService(Context.WindowService).JavaCast<IWindowManager>();
            SurfaceOrientation orientation = windowManager.DefaultDisplay.Rotation;
            bool isLandscape = orientation == SurfaceOrientation.Rotation90 || orientation == SurfaceOrientation.Rotation270;
            return isLandscape ? DeviceOrientation.Landscape : DeviceOrientation.Portrait;
#elif IOS
            UIInterfaceOrientation orientation = UIApplication.SharedApplication.StatusBarOrientation;
            bool isPortrait = orientation == UIInterfaceOrientation.Portrait || orientation == UIInterfaceOrientation.PortraitUpsideDown;
            return isPortrait ? DeviceOrientation.Portrait : DeviceOrientation.Landscape;
#else
            return DeviceOrientation.Undefined;
#endif
        }
    }
}

Or Partial classes

Shared code:

namespace InvokePlatformCodeDemos.Services.PartialMethods
{
    public partial class DeviceOrientationService
    {
        public partial DeviceOrientation GetOrientation();
    }
}

Platform code:

using Android.Content;
using Android.Runtime;
using Android.Views;

namespace InvokePlatformCodeDemos.Services.PartialMethods;

public partial class DeviceOrientationService
{
    public partial DeviceOrientation GetOrientation()
    {
        IWindowManager windowManager = Android.App.Application.Context.GetSystemService(Context.WindowService).JavaCast<IWindowManager>();
        SurfaceOrientation orientation = windowManager.DefaultDisplay.Rotation;
        bool isLandscape = orientation == SurfaceOrientation.Rotation90 || orientation == SurfaceOrientation.Rotation270;
        return isLandscape ? DeviceOrientation.Landscape : DeviceOrientation.Portrait;
    }
}

Public partial class does now work in the .Net Maui class library, does anyone know why? — Java_Dude, Nov 14 '22 at 13:14
@Java_Dude I have done it multiple times in my lib though https://github.com/FreakyAli/Maui.FreakyControls — FreakyAli, Jun 23 '23 at 09:21

score 5 · Answer 2 · answered Dec 11 '22 at 17:07

5

Instead of injecting your service implementations automatically:

[assembly: Dependency(typeof(MyService))]

Do it manually:

DependencyService.Register<IMyService, MyService>();

In your MauiApplication subclass (MauiWinUIApplication (windows)/MauiUIApplicationDelegate (ios)/ MauiApplication(android) ...etc.)

answered Dec 11 '22 at 17:07

Akli

1,351
1
15
28

Where do you do that in Maui class library if you want to build shared packages? – Emil Jun 22 '23 at 16:26
@Emil Subclass the MauiApplication for each platform (within your Maui class library, per folder platform), register your services there, then in each of your Maui App inherit from your subclass (for windows don't forget to update the Xaml as well). – Akli Jun 24 '23 at 07:04

score 0 · Answer 3 · answered Jul 25 '23 at 15:22

0

In MauiProgram.cs

builder.Services.AddSingleton<Interface, Implementation>();

answered Jul 25 '23 at 15:22

Pavlo Datsiuk

1,024
9
17

MAUI: DependencyService.Get() return null

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