Parameter is null instead of an id with ModalRoute.of()

Question

I am developing a mobile App with Flutter and Firebase.

I am trying to use pushNamed() and hand over a parameter. (an id)

I don't know how i could solve my problem.

Here is my Code:

@override
  void didChangeDependencies() {
    if (_isInit) {
      print(ModalRoute.of(context).settings.arguments);
      final productId = ModalRoute.of(context).settings.arguments;
      if (productId != null) {
        _editedAngebot = Provider.of<Angebote>(context).findByID(productId);
        _initValues = {
          'titel': _editedAngebot.titel,
          'beschreibung': _editedAngebot.beschreibung,
          'semester': _editedAngebot.semester.toString(),
          'fach': _editedAngebot.fach,
          'abteilung': _editedAngebot.abteilung,
        };
      }
    }
    _isInit = false;
    super.didChangeDependencies();
  }

And the other class, where I set the parameter. My "Angebot" object only has a default constructor.

trailing: isAllowed()
            ? IconButton(
                icon: Icon(Icons.edit),
                onPressed: () {
                  Navigator.of(context).maybePop();
                  Navigator.of(context)
                      .pushNamed('/editAngebot', arguments: id);
                })

Why is my ID null?

Answer 1

Your Id is null because you are popping a page first then pushing new page .

Use pushReplacementNamed()

Here is a code sample

import 'package:flutter/material.dart';

final Color darkBlue = Color.fromARGB(255, 18, 32, 47);

void main() {
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      debugShowCheckedModeBanner: false,
      home: FirstPage(),
      routes:{
        Secondpage.routeName:(context)=>Secondpage(),
      }
    );
  }
}

class FirstPage extends StatelessWidget {
  final String id = '01';
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Center(child:ElevatedButton(
        child: Text('GoTo secondPage'),
        onPressed: (){
          Navigator.of(context).pushReplacementNamed(Secondpage.routeName,arguments: id);
        },
      ))
    );
  }
}

class Secondpage extends StatelessWidget {
  static const routeName = 'secondpage';
  @override
  Widget build(BuildContext context) {
    final data = ModalRoute.of(context).settings.arguments as String;
    return Scaffold(
      body: Column(
        mainAxisAlignment: MainAxisAlignment.center,
        children: [
          Center(child:Text('$data')),
          ElevatedButton(
        child: Text('GoTo FirstPage'),
        onPressed: (){
          Navigator.of(context).pop();
        },
      )
        ],
      )
    );
  }
}