Using data binding inside monogame to control ad control display

March 07, 2014

I’ve already blogged a few times on using monogame with XAML. One thing that occurred to me recently was that I could leverage this in order to better control when the ad control appears in one of my games. Basically, my idea was that I could bind the main game page to a model, which determined whether the ad would be displayed.

Obviously, the difficulty here is that you need to pass the view model around your app. Monogame doesn’t seem to be very good at allowing you to do that, so I decided to use this approach (in app.xaml.cs):


    sealed partial class App : Application
    {
        private static GamePageViewModel \_gamePageViewModel;
        public static GamePageViewModel GamePageViewModel
        {
            get
            {
                if (\_gamePageViewModel == null)
                {
                    \_gamePageViewModel = new GamePageViewModel();
                }

                return \_gamePageViewModel;
            }
        }

A couple of notes on that code:

Yes, I could have simply instantiated the viewmodel at the start of the app.
Yes, it is static. This is so you can access it elsewhere.

The GamePageViewModel isn’t particularly noteworthy:


namespace MyGame.ViewModel
{
    public class GamePageViewModel : INotifyPropertyChanged
    {
        private bool \_showAds;
        public bool ShowAds
        {
            get { return \_showAds; }
            set
            {
                \_showAds = value;
                RaisePropertyChanged( "ShowAds");
            }
        }

        private void RaisePropertyChanged( string caller)
        {
            if (PropertyChanged != null)
            {
                PropertyChanged( this, new PropertyChangedEventArgs(caller));
            }
        }
        public event PropertyChangedEventHandler PropertyChanged;
    }
}

I do need to set this in code though; so when you display the GamePage:


         protected override void OnLaunched( LaunchActivatedEventArgs args)
        {
            var gamePage = Window.Current.Content as GamePage;

            // Do not repeat app initialization when the Window already has content,
            // just ensure that the window is active
            if (gamePage == null)
            {
                // Create a main GamePage
                gamePage = new GamePage(args.Arguments);

                // Set the DataContext to the static instance of the ViewModel
                gamePage.DataContext = App.GamePageViewModel;

You need to bind the ad control (use somthing like this - I haven’t detailed the code for the converter, but I’m sure 3 seconds of Internet searching will reveal a few thousand examples):

/>

What this allows me to do, from ANYWHERE in the game is this:

               
         private async static void purchaseCommandInvoked(Windows.UI.Popups.IUICommand command)
        {
            bool success = await License.PurchaseApp();

            if (success)
            {
                // Updating the view model here!
                App.GamePageViewModel.ShowAds = false;
            }
        }

Conclusion

So, nothing new here, but using binding inside Monogame didn’t occur to me immediately, so there must be a least some people in the same boat.