How to append new data in ListView Flutter - flutter

Question

I Wanna ask for my problem in flutter. How to append new data from another screen (has pop) to main screen (contain list view data from json) this is my code from main screen.
floatingActionButton: FloatingActionButton(
onPressed: () {
Navigator.push(
context,
MaterialPageRoute(
builder: (BuildContext context) => FormUser()))
.then((VALUE) {
/////////
Here for adding new data from VALUE into list view
/////
});
});
This my listview
Widget _buildListView(List<User> users) {
return ListView.separated(
separatorBuilder: (BuildContext context, int i) =>
Divider(color: Colors.grey[400]),
itemCount: users.length,
itemBuilder: (context, index) {
User user = users[index];
return ListTile(
leading: Icon(Icons.perm_identity),
title: Text(capitalize(user.fullName)),
subtitle: Text(user.gender),
trailing: Column(
mainAxisAlignment: MainAxisAlignment.spaceAround,
children: <Widget>[
Text(user.grade.toUpperCase()),
Text(user.phone)
],
),
);
},
);
}
}
This is return data from add screen
User{id: null, fullname: Camomi, gender: pria, grade: sma, phone: 082232, email: ade#gmul.com}
This is my class model of typedata
class User {
int id;
String fullName, gender, grade, phone, email;
User(
{this.id,
this.fullName,
this.gender,
this.grade,
this.phone,
this.email});
}

Answer 1

You add an element to your list of users. Then you call setState so your widget's build function gets called and builds the new view with the list of users that now contains the new element.
And please do not use .then() in your onPressed method. Make the method async and use await or if you really want to use .then(), at least return the Future it gives you.

Answer 2

You will need to do extra steps:
Wait for the result when calling push() method:
final result = await Navigator.push(...);
In your FormUser widget, when you finish entering data and press on Done or similar, you should return the created user:
// userData will be assigned to result on step 1 above. Then you add that result (user) to your list
Navigator.pop(context, userData);
You can find a very good tutorial here.

Answer 3

First of all make sure that Your class extends StatefulWidget.
I assume your list of users looks like this (or it's empty like [] ) :
List<User> users = [user1, user2, user3];
In Your FloatingActionButton in onPressed you should have this method (copy the content to onPressed or write a method like this somewhere in your code).
The method must be async to await the user
void _addUser() async {
final user = await Navigator.of(context).push(
MaterialPageRoute(
builder: (BuildContext context) => FormUser()));
if (user != null) {
setState(() => users.add(user));
}
}
This code should work fine, enjoy :)