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Transferring data from the android service to ContentPage in an application based on Xamarin Form

I have one application based on XamarinForms.

One background service that I created in an Android project, and this service would like to send data to ContentPage (which is located in PCL), which is displayed to the user.

How to transfer data to ContentPage (from xx.Droid project to PCL)?

One solution:

  • Create a class in PCL with a static variable (for example, var TEMP_VAR), to which the xxx.Droid project will be available.
  • Update the value of this static variable (TEMP_VAR) from the service class from the xxx.Droid project.
  • You must create a Notifier for this static variable (TEMP_VAR)
  • If necessary, refresh the content page using the MessageCenter engine.

If there is any better solution, could you please provide me?

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1 answer

This can be achieved using the C # concept.

  • Dependency Service
  • Event

It is necessary to have 4 classes for such an implementation:

  • An interface in the PCL (e.g. CurrentLocationService.cs) with event handlers defined in it.

namespace NAMESPACE { public interface CurrentLocationService { void start(); event EventHandler<PositionEventArgs> positionChanged; } }
  1. Implementing the PCL interface in an xxx.Droid project (e.g. CurrentLocationService_Android.cs) using the Dependency service

 class CurrentLocationService_Android : CurrentLocationService { public static CurrentLocationService_Android mySelf; public event EventHandler<PositionEventArgs> positionChanged; public void start() { mySelf = this; Forms.Context.StartService(new Intent(Forms.Context, typeof(MyService))); } public void receivedNewPosition(CustomPosition pos) { positionChanged(this, new PositionEventArgs(pos)); } }
  1. ContentPage in PCL - which will have an interface implementation object. Object can be obtained

 public CurrentLocationService LocationService { get { if(currentLocationService == null) { currentLocationService = DependencyService.Get<CurrentLocationService>(); currentLocationService.positionChanged += OnPositionChange; } return currentLocationService; } } private void OnPositionChange(object sender, PositionEventArgs e) { Debug.WriteLine("Got the update in ContentPage from service "); }
  1. Background service in the xxx.Droid project. This service will have a link to the implementation of the dependency service CurrentLocationService.cs

 [Service] public class MyService : Service { public string TAG = "MyService"; public override IBinder OnBind(Intent intent) { throw new NotImplementedException(); } public override StartCommandResult OnStartCommand(Android.Content.Intent intent, StartCommandFlags flags, int startId) { Log.Debug(TAG, TAG + " started"); doWork(); return StartCommandResult.Sticky; } public void doWork() { var t = new Thread( () => { Log.Debug(TAG, "Doing work"); Thread.Sleep(10000); Log.Debug(TAG, "Work completed"); if(CurrentLocationService_Android.mySelf != null) { CustomPosition pos = new CustomPosition(); pos.update = "Finally value is updated"; CurrentLocationService_Android.mySelf.receivedNewPosition(pos); } StopSelf(); }); t.Start(); } }

Note. The PositionEventArgs class must be created according to the use for transferring data between the service and ContentPage.

It works for me like a charm.

Hope this would be helpful for you.

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