var whatsappURl_android = "whatsapp://send?phone="+whatsapp+"&text=hello";
  var whatappURL_ios ="https://wa.me/$whatsapp?text=${Uri.parse("hello")}";
  if(Platform.isIOS){
    // for iOS phone only
    if( await canLaunch(whatappURL_ios)){
       await launch(whatappURL_ios, forceSafariVC: false);
    }else{
      ScaffoldMessenger.of(context).showSnackBar(
          SnackBar(content: new Text("whatsapp no installed")));

    }

  }else{
    // android , web
    if( await canLaunch(whatsappURl_android)){
      await launch(whatsappURl_android);
    }else{
      ScaffoldMessenger.of(context).showSnackBar(
          SnackBar(content: new Text("whatsapp no installed")));

    }


  }