public MainPageViewModel(INavigationService navigationService)
: base(navigationService)
{
Xamarin.Forms.DependencyService.Register <IBluetoothService>();
bluetoothService = (DependencyService.Get <IBluetoothService>());
bluetoothService.Init();
ShowDeviceNameAlert = new DelegateCommand <string>(alertDeviceName);
Title = "Main Page";
}