internal Platform(FormsApplicationPage page) { _page = page; var busyCount = 0; MessagingCenter.Subscribe(this, Page.BusySetSignalName, (Page sender, bool enabled) => { busyCount = Math.Max(0, enabled ? busyCount + 1 : busyCount - 1); }); MessagingCenter.Subscribe <Page, AlertArguments>(this, Page.AlertSignalName, OnPageAlert); MessagingCenter.Subscribe <Page, ActionSheetArguments>(this, Page.ActionSheetSignalName, OnPageActionSheet); }