-1.5 C
New York
Thursday, February 2, 2023

Flutter: Using widget.Variable before the build method

In Flutter, you can access variables from stateful widget class with the widget keyword like this:

class ChildPage extends StatefulWidget {
  final String someText;
  const ChildPage({Key? key, required this.someText}) : super(key: key);
  @override
  _ChildPageState createState() => _ChildPageState();
}

class _ChildPageState extends State<ChildPage> {
  @override
  Widget build(BuildContext context) {
    return Center(
      child: Text(widget.someText),
    );
  }
}

But in some cases, you may need to get the variables from the stateful widget before Widget build(BuildContext context). How to do so? The solution is to use the initState method.Advertisements

class ChildPage extends StatefulWidget {
  final String someText;
  const ChildPage({Key? key, required this.someText}) : super(key: key);
  @override
  _ChildPageState createState() => _ChildPageState();
}

class _ChildPageState extends State<ChildPage> {
  late String displayText;
  @override
  void initState() {
    displayText = widget.someText + " " + "Some extra text!";
    super.initState();
  }

  @override
  Widget build(BuildContext context) {
    return Center(
      child: Text(displayText),
    );
  }
}

The Full Example

Screenshot:

The complete code in main.dart:

import 'package:flutter/material.dart';

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

class MyApp extends StatelessWidget {
  const MyApp({Key? key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return const MaterialApp(
      // Hide the debug banner
      debugShowCheckedModeBanner: false,
      title: 'Kindacode.com',
      home: MyHomePage(),
    );
  }
}

class MyHomePage extends StatelessWidget {
  const MyHomePage({Key? key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: const Text('Kindacode.com'),
      ),
      body: const SafeArea(
        child: ChildPage(
          someText: 'Have a nice day!',
        ),
      ),
    );
  }
}

class ChildPage extends StatefulWidget {
  final String someText;
  const ChildPage({Key? key, required this.someText}) : super(key: key);
  @override
  _ChildPageState createState() => _ChildPageState();
}

class _ChildPageState extends State<ChildPage> {
  late String displayText;
  @override
  void initState() {
    displayText = widget.someText + " " + "Some extra text!";
    super.initState();
  }

  @override
  Widget build(BuildContext context) {
    return Center(
      child: Text(displayText),
    );
  }
}

Hope this helps. Further reading:

AdvertisementsYou can also take a tour around our Flutter topic page and Dart topic page to see the latest tutorials and examples.

Advertisements

Related Articles

LEAVE A REPLY

Please enter your comment!
Please enter your name here

Latest Articles