Flutter Navigator.pop won't send data back - android-studio

Question

This is my code so far. I dont know whats wrong, I tried a lots of youtube turolial and other things as well, but its looks like the pop wont give back the correct data. I really need help, i spend 2 days already
void main() {
List<String> names = [];
List<String> mgs = [];
runApp(MaterialApp(
title: 'Returning Data',
home: HomeScreen(names, mgs),
));
}
class HomeScreen extends StatelessWidget {
List<String> names = [];
List<String> mgs = [];
HomeScreen(this.names, this.mgs);
#override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
backgroundColor: Colors.blue,
title: Text("Project_Drink"),
),
body: Container(
child: Column(
children: <Widget>[
new Expanded(
child: ListView.builder
(
itemCount: mgs.length,
itemBuilder: (context, Index) {
return Text("Name: " + names[Index]
+" "+ "Mg: " + mgs[Index]);
}
)
)
],
),
),
bottomNavigationBar :BottomAppBar (
child: Padding(
padding: const EdgeInsets.all(8.0),
child: Row(
children: <Widget>[
const Expanded(child: Text("TOTAL : 200")),
FloatingActionButton(
onPressed: () {
Navigator.push(
context,
MaterialPageRoute(builder: (context) => AddProduct()),
);
},
child: Icon(Icons.add),
),
],
),
),
),
);
}
}
This is the AddProduct i want this to send back the data and then i should be able to put in into a list.Lika a not pad
class AddProduct extends StatefulWidget {
#override
State createState() => new _AddProductState();
}
class _AddProductState extends State<AddProduct> {
List<String> names = [];
List<String> mgs = [];
//final TextEditingController eCtrl = new TextEditingController();
final nameController = TextEditingController();
final mgController = TextEditingController();
#override
Widget build (BuildContext ctxt) {
return new Scaffold(
appBar: AppBar(
backgroundColor: Colors.blue,
title: Text("New Drink"),
),
body: new Column(
children: <Widget>[
new TextField(
decoration: InputDecoration(
hintText: "Name",
),
controller: nameController,
),
new TextField(
decoration: InputDecoration(
hintText: "Mg",
suffixText: "Mg",
),
controller: mgController,
),
RaisedButton(
onPressed: (){
names.add(nameController.text);
mgs.add(mgController.text);
setState(() {});
nameController.clear();
mgController.clear();
Navigator.pop(context, names + mgs);
},
child: Text("ADD"),
),
],
)
);
}
}

Answer 1

I moved your lists to HomeScreen widget instead of main function. Your main function should just run the app
void main() {
runApp(
MaterialApp(
title: 'Returning Data',
home: HomeScreen(),
),
);
}
And I convert your HomeScreen widget to StatefulWidget insted of StatelessWidget because when you add new items and display it screen your state will change and StatelessWidget is not able to do that. It will be something like that
Navigator.push returns a future value so if you want to declare a variable with the data comes from that, you need to await for it. After you get the data you can add them into your lists but it needs to be inside setState function to update UI
class HomeScreen extends StatefulWidget {
#override
_HomeScreenState createState() => _HomeScreenState();
}
class _HomeScreenState extends State<HomeScreen> {
List<String> names = [];
List<String> mgs = [];
#override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
backgroundColor: Colors.blue,
title: Text("Project_Drink"),
),
body: Container(
child: Column(
children: <Widget>[
new Expanded(
child: ListView.builder(
itemCount: mgs.length,
itemBuilder: (context, index) {
return Text("Name: " + names[index] + " " + "Mg: " + mgs[index]);
}
),
),
],
),
),
bottomNavigationBar: BottomAppBar(
child: Padding(
padding: const EdgeInsets.all(8.0),
child: Row(
children: <Widget>[
Expanded(child: Text("TOTAL : 200")),
FloatingActionButton(
onPressed: () async {
// Navigator.push returns a future value so you need to await for it
var data = await Navigator.push(
context,
MaterialPageRoute(builder: (context) => AddProduct()),
);
// After you get the data from the other page you need to add them into your lists inside setState function to update UI
setState(() {
names.add(data[0]);
mgs.add(data[1]);
});
},
child: Icon(Icons.add),
),
],
),
),
),
);
}
}
I didn't change anything in your AddProduct widget.
class AddProduct extends StatefulWidget {
#override
State createState() => new _AddProductState();
}
class _AddProductState extends State<AddProduct> {
List<String> names = [];
List<String> mgs = [];
//final TextEditingController eCtrl = new TextEditingController();
final nameController = TextEditingController();
final mgController = TextEditingController();
#override
Widget build (BuildContext ctxt) {
return Scaffold(
appBar: AppBar(
backgroundColor: Colors.blue,
title: Text("New Drink"),
),
body: Column(
children: <Widget>[
TextField(
decoration: InputDecoration(
hintText: "Name",
),
controller: nameController,
),
TextField(
decoration: InputDecoration(
hintText: "Mg",
suffixText: "Mg",
),
controller: mgController,
),
RaisedButton(
onPressed: (){
names.add(nameController.text);
mgs.add(mgController.text);
setState(() {});
nameController.clear();
mgController.clear();
Navigator.pop(context, names + mgs);
},
child: Text("ADD"),
),
],
)
);
}
}
Although this code should work as you want, I would suggest you to have a look at some State Management methods such as Provider, Bloc and etc. It will be more effective to create what you want to do.

Answer 2

try this one with simple way , when press then call this method
goToView() async {
bool data=await Navigator.push(context, new CupertinoPageRoute(builder: (BuildContext context) {
return new CoolForgot();
}));
print(data);
}
My Next View is Forgot Screen so i have used CoolForgot(), you can use as per your requirement.
then when press on back button in Next View(In my case CoolForgot()) called this
Navigator.pop(context,true);
I have pass bool value and get bool value , you can pass any type of object and get from it.