pass parameter to another component - null - flutter

Question

Follow the excerpt that I send and the other that I receive the parameter. but it's coming null
Usuario usuario = Usuario();
usuario.email = email;
usuario.senha = senha;
//cadastrar ou logar
if( _cadastrar ){
print(usuario);
Navigator.of(context).pushNamed('/termos-aceite', arguments: usuario.email);
}else{
//Logar
_logarUsuario(usuario);
}
// second screen
Widget build(BuildContext context) {
setState(() {
args = ModalRoute.of(context).settings.arguments;
});
print('args');
print(args); //value is null

Answer 1

you need to send a map not a property
Usuario usuario = Usuario();
usuario.email = email;
usuario.senha = senha;
//cadastrar ou logar
if( _cadastrar ){
print(usuario);
Navigator.of(context).pushNamed('/termos-aceite', arguments: {"email":usuario.email});
}else{
//Logar
_logarUsuario(usuario);
}
when you try to get the values cast the arguments as Map of String Object like this and and use the property key you to get the data
setState(() {
args = ModalRoute.of(context).settings.arguments as Map<String, Object>;
});
print('args');
print(args["email"]); //value is email's value

Answer 2

There is a better and generic approach to do that, and I would suggest you to do that.
So we can do this via using the Constructor method, which accepts some variable with values, in your case this is the page, i.e., /termos-aceite. Now taking the Page name as Termos for this /termos-aceite. Let us see how this works.
class Termos extends StatelessWidget {
// Declare a field that holds the Todo.
final dynamic email;
// In the constructor, require a Todo.
DetailScreen({Key key, #required this.email}) : super(key: key);
//To use that, you can simply do
print(args);
setState(() {
args = this.email;
});
}
And In order to pass it to the page, in this case to Termos, we do this using your code only
Usuario usuario = Usuario();
usuario.email = email;
usuario.senha = senha;
//cadastrar ou logar
if( _cadastrar ){
print(usuario);
// Read about MaterialPageRoute() here
// https://api.flutter.dev/flutter/material/MaterialPageRoute-class.html
Navigator.push(context, MaterialPageRoute(
builder: (context) => Termos(email: email)
));
}else{
//Logar
_logarUsuario(usuario);
}
I hope you will get it what you want. Also, please keep googling these things about flutter. It is cool, and you will find great things there in the documentation itself. I am anyway listing down some of the links for you, hope that would be a learning experience for you. Keep learning
Flutter Dev Docs
Naivgate With Argument
Passing data to a new screen