public GroupPage()
{
InitializeComponent ();
activityPage = new ActivityPage ();
eventPage = new EventPage ();
memberPage = new MemberPage ();
filePage = new FilePage();
Children.Add (activityPage);
Children.Add (eventPage);
Children.Add (memberPage);
Children.Add (filePage);
MessagingCenter.Subscribe<Xamarin.Forms.Application> (App.Current, "select_group", async(sender) => {
var app = (App)App.Current;
BindingContext = app.CurrentGroup;
});
}