如何根据 Xamarin Forms 中的当前页面广播消息

Question

I have a Xamarin Forms solution like this:

    Solution:
 |- Forms.App
 |   |- App.cs
 |   |- MyViewPage.xaml
 |   |- MyViewModel.cs
 |   | ...
 |   
 |- Droid Project
 |   |- TriggerService.cs
 |   | ...

I'm using a BroadcastReceiver with Intent filter in Android project to send Events when some physical trigger is pressed, so far this is working for me but now I'm trying to adapt that broadcast message to do different things based on from which page it was pressed.

It will be different to me to press a trigger from some Page than other, here is my current implementation on relevant classes:

Trigger Service

[BroadcastReceiver(Enabled = true, Exported = false)]
[IntentFilter(new[] { "android.TRIGGER" })]
public class TriggerService : BroadcastReceiver, ITriggerService
{
    public override void OnReceive(Context context, Intent intent)
    {
        //Here I need to identify the Page where I'm located
        var page = "MyViewPage" // should replace by some mechanism to GetCurrentPage();

        switch (page)
        {
            case "MyViewPage":
                Xamarin.Forms.MessagingCenter.Send<TriggerService>(this, "TRIGGER_MyViewPage");
                break;
            case "MyViewPage2":
                Xamarin.Forms.MessagingCenter.Send<TriggerService>(this, "TRIGGER_MyViewPage2");
                break;
            case "MyViewPage3":
                Xamarin.Forms.MessagingCenter.Send<TriggerService>(this, "TRIGGER_MyViewPage3");
                break;
        }
    }
}

Here MyViewPage

[XamlCompilation(XamlCompilationOptions.Compile)]
public partial class MyViewPage : ContentPage
{
    private MyViewModel _viewModel;

    public MyViewPage()
    { 
        InitializeComponent();
        _viewModel = new MyViewModel();
        MessagingCenter.Subscribe<TriggerService>(this, "TRIGGER_MyViewPage", (sender) =>
        {
            //Do something different for this Page when trigger pressed
        });
    }
}

To summarize I'm looking for a way to get the current Page from Android level when using Xamarin Forms, or maybe some orientation on a better way to implement such mechanism.

Answer 1

I resolved it inverting control and handling different behaviors at Forms layer instead of Android which I think is better solution. I'll show below in case helps someone else:

Trigger Service (Broadcast):

[BroadcastReceiver(Enabled = true, Exported = false)]
[IntentFilter(new[] { "android.TRIGGER" })]
public class TriggerService : BroadcastReceiver, ITriggerService
{
    public override void OnReceive(Context context, Intent intent)
    {
        //I just broadcast the message no matter which page I'm in
        Xamarin.Forms.MessagingCenter.Send<TriggerService>(this, "TRIGGER");
    }
}

AppShell Class:

public partial class AppShell : Xamarin.Forms.Shell
{
    public AppShell()
    {
        InitializeComponent();
        MessagingCenter.Subscribe<ITriggerService>(this, "TRIGGER", async (sender) =>
        {
            //Here I get the current page and do something different based on location
            var current = Shell.Current?.CurrentItem?.CurrentItem?.Route?.Replace("IMPL_","");
            if (current != null)
            {
                switch (current)
                {
                    case "MyViewPage":
                        CrossToastPopUp.Current.ShowToastMessage($"Trigger was pressed from: {current}");
                        break;
                    case "MyViewPage2":
                        CrossToastPopUp.Current.ShowToastMessage($"Trigger was pressed from: {current}");
                        break;
                    default:
                        break;
                }
            }    
        });
    }
}