is it possible to pass the parameter without required in flutter-CodePudding

is it possible to pass this.title without required, i have seen some tutorial they doing so, but when i try it asks me to add required to this.title. As my 2 screen doesn't contain appBar title i want to pass it without required. is it possible?

here my code works fine if i add required to this.title.

import 'package:flutter/material.dart';
import 'package:flutter_bloc/flutter_bloc.dart';

import '../../logic/cubit/counter_cubit.dart';

class HomeScreen extends StatefulWidget {
const HomeScreen({Key? key,  this.title}) : super(key: key);

final String title;

@override
State<HomeScreen> createState() => _HomeScreenState();
}

class _HomeScreenState extends State<HomeScreen> {
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text(widget.title),
),
[SS of code][1]

CodePudding user response：

The title needs to be required because you made it not nullable. You can make it nullable if the title is optional:

class HomeScreen extends StatefulWidget {
  const HomeScreen({Key? key, this.title}) : super(key: key);

  final String? title;

  @override
  State<HomeScreen> createState() => _HomeScreenState();
}

However, now you need to handle the fact that you may not have a title in your build function:

class _HomeScreenState extends State<HomeScreen> {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text(widget.title ?? "NO TITLE!?!"),
      ),
     );
  }
}

Obviously you don't want "NO TITLE!?!" to be in your title, but since I don't know what you want instead, you will have to change that part.

CodePudding user response：

In addition to the answer given by @nvoigt, you can also supply a default value instead of making title nullable:

class HomeScreen extends StatefulWidget {
  const HomeScreen({Key? key, this.title = 'Home Screen'}) : super(key: key);

  final String title;

  @override
  State<HomeScreen> createState() => _HomeScreenState();
}

This way, you don't have to supply a title, and if you don't, it will use Home Screen as the title instead.