Pass variable values from Xamarin.Android to Xamarin.Forms

Question

I get messages in Xamarin.Android and I need pass it to Xamarin.Forms app. What I came up with at the moment is dependency injection. I has defined the interface:

public interface IReceived
{
    event OnReceived Received;
}

And its implementation inside IncomingSms class inherited from BroadcastReceiver for messages listening

[assembly: Dependency(typeof(XxmsApp.Api.IncomingSms))]
namespace XxmsApp.Api
{


    // [BroadcastReceiver(Enabled = true, Exported = true)]

    [BroadcastReceiver(Enabled = true, Label = "SMS Receiver")]
    [IntentFilter(new string [] { Telephony.Sms.Intents.SmsReceivedAction })]           // "android.provider.Telephony.SMS_RECEIVED"
    public class IncomingSms : BroadcastReceiver, IReceived
    {

        public event OnReceived Received;

        public override void OnReceive(Context context, Intent intent)
        {

            if (intent.Action != Telephony.Sms.Intents.SmsReceivedAction) return;

            SmsMessage[] messages = Telephony.Sms.Intents.GetMessagesFromIntent(intent);

            OnMessagesReiceved(messages);

        }

        private void OnMessagesReiceved(SmsMessage[] messages)
        {

            var smsMesages = new List<(string Address, string Message)>();
            var XMessages = new List<XxmsApp.Model.Message>();

            for (var i = 0; i < messages.Length; i++)
            {
                smsMesages.Add((messages[i].OriginatingAddress, messages[i].MessageBody));


                XMessages.Add(new XxmsApp.Model.Message
                {
                    Address = messages[i].OriginatingAddress,
                    Value = messages[i].MessageBody
                });

            }

            Received?.Invoke(XMessages);

        }
    }
}

And I have subscribed to the event Received

    public App()
    {

        DBUpdates();

        MainPage = (new MasterDetailPage()
        {
            Master = new MenuPage { Title = "Title" },
            Detail = new NavigationPage(new XxmsApp.MainPage()) { BarBackgroundColor = Color.Black }
        });

        xMessages = DependencyService.Get<XxmsApp.Api.IReceived>();
        xMessages.Received += XMessages_Received;//*/

    }

    private void XMessages_Received(IEnumerable<Model.Message> message)
    {
          // ...
    }

It's work without some errors. But when raised the line Received?.Invoke(XMessages); Received always is null. And I can't catch the event (moment of message coming) in my main app Xamarin.Forms

How can do this?

Answer 1

Agree with Jason, you can use the MessagingCenter to achieve it. Here is code in the SmsBroadcastRceiver

    [BroadcastReceiver(Enabled = true, Exported = true)]
    [IntentFilter(new[] { "android.provider.Telephony.SMS_RECEIVED" })]
    public class SmsBroadcastRceiver : BroadcastReceiver
    {

        public SmsBroadcastRceiver()
        {

        }



        public override void OnReceive(Context context, Intent intent)
        {
            var msgs = Telephony.Sms.Intents.GetMessagesFromIntent(intent);

            List<string> msgList = new List<string>();
            foreach (var msg in msgs)
            {
                msgList.Add(msg.DisplayMessageBody);

            }

            MessagingCenter.Send<List<string>>(msgList, "MyMessage");
        }
    }

You can receive the message in PCL background code.

    [DesignTimeVisible(false)]
    public partial class MainPage : ContentPage
    {
        public MainPage()
        {
            InitializeComponent();
            MessagingCenter.Subscribe<List<string>>(this, "MyMessage", (expense) =>
            {
                List<string> mylist= expense as List<string>;
                string allText= "";
                foreach (string item in mylist)
                {
                    allText += item+"  ";
                }
                editorSms.Text = allText;
            });



        }



        private void Button_Clicked(object sender, EventArgs e)
        {
            Xamarin.Forms.DependencyService.Get<ISmsReader>().GetSmsInbox();
        }
    }

Here is my running gif.

Here is code demo code(Note:I do not achieve the runtime permission, you should add the permission manually).

https://github.com/851265601/BroadcastReceSMS