Avalonia/src/Android/Avalonia.Android/Platform/AndroidActivatableLifetime.cs

using System;
using Android.App;
using Avalonia.Controls.ApplicationLifetimes;

namespace Avalonia.Android.Platform;

internal class AndroidActivatableLifetime : IActivatableLifetime
{
    private IAvaloniaActivity _activity;

    public IAvaloniaActivity Activity
    {
        get => _activity;
        set
        {
            if (_activity is not null)
            {
                _activity.Activated -= ActivityOnActivated;
                _activity.Deactivated -= ActivityOnDeactivated;
            }

            _activity = value;

            if (_activity is not null)
            {
                _activity.Activated += ActivityOnActivated;
                _activity.Deactivated += ActivityOnDeactivated;
            }
        }
    }
    
    public event EventHandler<ActivatedEventArgs> Activated;
    public event EventHandler<ActivatedEventArgs> Deactivated;

    public bool TryLeaveBackground() => (_activity as Activity)?.MoveTaskToBack(true) == true;
    public bool TryEnterBackground() => false;

    private void ActivityOnDeactivated(object sender, ActivatedEventArgs e)
    {
        Deactivated?.Invoke(this, e);
    }

    private void ActivityOnActivated(object sender, ActivatedEventArgs e)
    {
        Activated?.Invoke(this, e);
    }
}