Using BuildContext outside build function

Question

I have a function that builds a widget to be able to reuse it, and in that function I want to set the text theme. My problem is that to do that I need to access the BuildContext to do so. The only way I can think of is to pass it as a parameter in every function call, but it feels like there must be a simpler method. Or is this the best way to do it?

Here is the current code:

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

import 'package:snapping_page_scroll/snapping_page_scroll.dart';

void main() => runApp(MaterialApp(
      theme: ThemeData(
        backgroundColor: Color(0xff121217),
         textTheme: TextTheme(
           headline: TextStyle(fontSize: 40)
         )
      ),
      home: SplashScreen(),
    ));

class SplashScreen extends StatefulWidget {
  @override
  _SplashScreenState createState() => _SplashScreenState();
}

class _SplashScreenState extends State<SplashScreen> {
  @override
  void initState() {
    super.initState();
    loadData();
  }

  //Simulates loading of data
  Future<Timer> loadData() async {
    return new Timer(Duration(seconds: 1), onDoneLoading);
  }

  onDoneLoading() async {
    Navigator.of(context).push(MaterialPageRoute(builder: (context) => Home()));
  }

  @override
  Widget build(BuildContext context) {
    return Container(
      color: Color(0xff121217),
      child: Padding(
        padding: const EdgeInsets.all(20),
        child: Image.asset('assets/logo.png'),
      ),
    );
  }
}

class Home extends StatelessWidget {

  Widget page(text, color, context){
    return Container(
      color: color,
      child: Align(
        alignment: Alignment(0, 0.5),
        child: Text(text, style: Theme.of(context).textTheme.headline,),
      ),
    );
  }

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        appBar: AppBar(),
        body: SnappingPageScroll(
          children: <Widget>[
            page('Page 1', Colors.orange, context),
            page('Page 2', Colors.green, context),
          ],
        ),
      ),
    );
  }
}

Filip P. · Accepted Answer · 2019-11-04 22:06:22Z

8

You can use builder widget. ... https://api.flutter.dev/flutter/widgets/Builder-class.html

answered Nov 4, 2019 at 22:06

Filip P.

1,3641 gold badge9 silver badges18 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

McGuy Over a year ago

This would be helpful if it gave more information.

lazos · Accepted Answer · 2019-11-04 23:02:01Z

You have access to BuildContext inside build method.

So you can move your place() function inside build.

Widget build(BuildContext context) {
  page(text, color) {
    return Container(
      color: color,
      child: Align(
        alignment: Alignment(0, 0.5),
        child: Text(
          text,
          style: Theme.of(context).textTheme.headline,
        ),
      ),
    );
  }

  return MaterialApp(
    home: Scaffold(
      appBar: AppBar(),
      body: Column(
        children: <Widget>[
          page('Page 1', Colors.orange),
          page('Page 2', Colors.green),
        ],
      ),
    ),
  );
}

Also in cases like yours a good pattern would be to create your own reusable Page widget and pass your parameters via constructor.

class Home extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        appBar: AppBar(),
        body: Column(
          children: <Widget>[
            _Page(text: 'Page 1', color: Colors.orange),
            _Page(text: 'Page 2', color: Colors.green),
          ],
        ),
      ),
    );
  }
}

class _Page extends StatelessWidget {
  const _Page({
    Key key,
    @required this.color,
    @required this.text,
  }) : super(key: key);

  final Color color;
  final String text;
  @override
  Widget build(BuildContext context) {
    return Container(
      color: color,
      child: Align(
        alignment: Alignment(0, 0.5),
        child: Text(
          text,
          style: Theme.of(context).textTheme.headline,
        ),
      ),
    );
  }
}

Lojith Vinsuka · Accepted Answer · 2021-12-11 07:56:08Z

1

Convert stateless widget to a stateful widget :)

Errors gone :)

answered Dec 11, 2021 at 7:56

Lojith Vinsuka

1,0471 gold badge14 silver badges8 bronze badges

Comments

Ebrar Küçükşahin · Accepted Answer · 2023-04-13 00:06:38Z

1

Define a variable from the BuildContext class at the top (for example, its name is a). Sync variable a to context under build function You can use variable a anywhere you want.

answered Apr 13, 2023 at 0:06

Ebrar Küçükşahin

111 bronze badge

1 Comment

Community Over a year ago

Your answer could be improved with additional supporting information. Please edit to add further details, such as citations or documentation, so that others can confirm that your answer is correct. You can find more information on how to write good answers in the help center.

Louise · Accepted Answer · 2023-10-07 05:34:14Z

The Theme is usually an object that could be accessed from everywhere in your code to maintain uniform UI and consistency.

Assuming you have different themes for different parts of your app (via nested Navigators, etc.), I believe that's the only time where you need the widget's BuildContext to find the Theme it's located under. In that case, I agree with Filip's answer about using a Builder widget.

I like to share another way to go about it is by using GlobalKeys, supplying it to a nested Navigator widget, and accessing declared key in the function. This is for those that need extra assurance that they're using the right theme. But in most cases (probably all), Flutter should be able to detect the right Theme which the BuildContext is under.

McGuy · Accepted Answer · 2024-05-01 17:58:26Z

-1

Wrap the function with a Builder, and you will have access to the BuildContext.

answered May 1, 2024 at 17:58

McGuy

881 silver badge14 bronze badges

Collectives™ on Stack Overflow

Using BuildContext outside build function

6 Answers 6

1 Comment

Comments

Comments

1 Comment

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

6 Answers 6

1 Comment

Comments

Comments

1 Comment

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related