How to adjust TextField width? - flutter

Question

I'm re-writing a simple app which calculates averages. However, I have a hard time with a TextField. I would like it to be exactly as on a first screenshot.
The TextField's width is stretched, I don't want that. I want it to be exactly as it is on the screenshot.
Desired look:
What I have:
Code:
import 'package:flutter/material.dart';
import 'package:easy_localization/easy_localization.dart';
class ArithmeticAverageScreen extends StatelessWidget {
#override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text('arithmetic_average_title').tr(),
),
body: Container(
padding: EdgeInsets.all(16.0),
child: Column(
children: <Widget>[
Card(
child: Container(
padding: EdgeInsets.symmetric(vertical: 20.0),
child: Column(
mainAxisSize: MainAxisSize.min,
children: <Widget>[
ListTile(
leading: Icon(Icons.help),
title: Text('arithmetic_average_help').tr(),
subtitle: Text('arithmetic_average_help_content').tr(),
)
],
),
)
),
SizedBox(height: 16.0),
Card(
child: Container(
padding: EdgeInsets.symmetric(vertical: 20.0, horizontal: 20.0),
child: Column(
mainAxisSize: MainAxisSize.min,
crossAxisAlignment: CrossAxisAlignment.stretch,
children: <Widget>[
Text('arithmetic_average_your_grades', style: Theme.of(context).textTheme.headline5).tr(),
SizedBox(height: 16.0),
Text('arithmetic_average_grades_one_at_a_time', style: Theme.of(context).textTheme.headline6,).tr(),
SizedBox(height: 16.0),
Text('arithmetic_average_grade', style: Theme.of(context).textTheme.subtitle2).tr(),
TextField()
],
),
),
)
],
),
)
);
}
}

Answer 1

This will help you make generic width on all devices, so here width * 0.3 means it will take 30% of the screen width
Container(
width: MediaQuery.of(context).size.width * 0.3,
child: TextField(),
)

Answer 2

Use Row Widget, and put Expanded Widget as child Widget and inside that put your widgets, as Expanded will take up equal space.
return Row(
children: [
Expanded(
child: TextField();
),
Expanded(
child: Button();
)
],
);

Answer 3

When ever you want to play with height and width you can use the widget Container.If you want to play with a property which cannot found in the widget you are using wrap it with a widget with that property will help you.
Container(
margin: const EdgeInsets.only(right: 150),
child: new TextField(
decoration: new InputDecoration(
hintText: 'Grade',
)
)
)

Answer 4

You can try to wrap your TextField and Button with two Flexible widgets and apply desired proportions, e.g. 1:2 which would give you following result:
Row(
children: [
Flexible(
flex: 1,
child: TextField(),
),
Flexible(
flex: 2,
child: RaisedButton(
child: Text('Hello'), onPressed: () {}),
)
],
)
],
You can also replace the first Flexible with SizedBox and set an exact value, e.g:
Row(
children: [
SizedBox(
width: 100.0,
child: TextField(),
),
Flexible(
flex: 2,
child: RaisedButton(
child: Text('Hello'), onPressed: () {}),
)
],
)
],
TextField doesn't have an intrinsic size (width) constraint so it will always try to occupy all horizontal space. Flexible allows to constraint it to desired width in a Row.
Full example on DartPad.