MainApplication.cs

public sealed class MainApplication : MainApplicationBase, ILifecycleObserver
{
  private readonly ILogManager _logManager = ...;

  public override void OnCreate()
  {
      base.OnCreate();

      RegisterActivityLifecycleCallbacks(new LoggingActivityLifecycleListener(_logManager));
  }
}

private sealed class LoggingActivityLifecycleListener : Java.Lang.Object, IActivityLifecycleCallbacks
{
    private readonly ILogger _logger;

    public LoggingActivityLifecycleListener(ILogManager logManager)
    {
        _logger = logManager.GetLogger<LoggingActivityLifecycleListener>();
    }

    public void OnActivityCreated(Activity activity, Bundle savedInstanceState)
    {
        _logger.Info($"OnActivityCreated: {activity.GetType().Name}");
    }

    public void OnActivityDestroyed(Activity activity)
    {
        _logger.Info($"OnActivityDestroyed: {activity.GetType().Name}");
    }

    public void OnActivityPaused(Activity activity)
    {
        _logger.Info($"OnActivityPaused: {activity.GetType().Name}");
    }

    public void OnActivityResumed(Activity activity)
    {
        _logger.Info($"OnActivityResumed: {activity.GetType().Name}");
    }

    public void OnActivitySaveInstanceState(Activity activity, Bundle outState)
    {
        _logger.Info($"OnActivitySaveInstanceState: {activity.GetType().Name}");
    }

    public void OnActivityStarted(Activity activity)
    {
        _logger.Info($"OnActivityStarted: {activity.GetType().Name}");
    }

    public void OnActivityStopped(Activity activity)
    {
        _logger.Info($"OnActivityStopped: {activity.GetType().Name}");
    }
}