Is there a simple (non-LayoutBuilder) way to size an element relative to screen size (width/height)? For example: how do I set the width of a CardView to be 65% of the screen width.
It can't be done inside the build method (obviously) so it would have to be deferred until post build. Is there a preferred place to put logic like this?
This is a supplemental answer showing the implementation of a couple of the solutions mentioned.
If you have a single widget you can use a FractionallySizedBox widget to specify a percentage of the available space to fill. Here the green Container is set to fill 70% of the available width and 30% of the available height.
Widget myWidget() {
return FractionallySizedBox(
widthFactor: 0.7,
heightFactor: 0.3,
child: Container(
color: Colors.green,
),
);
}
The Expanded widget allows a widget to fill the available space, horizontally if it is in a row, or vertically if it is in a column. You can use the flex property with multiple widgets to give them weights. Here the green Container takes 70% of the width and the yellow Container takes 30% of the width.
If you want to do it vertically, then just replace Row with Column.
Widget myWidget() {
return Row(
children: <Widget>[
Expanded(
flex: 7,
child: Container(
color: Colors.green,
),
),
Expanded(
flex: 3,
child: Container(
color: Colors.yellow,
),
),
],
);
}
Here is the main.dart code for your reference.
import 'package:flutter/material.dart';
void main() => runApp(MyApp());
class MyApp extends StatelessWidget {
@override
Widget build(BuildContext context) {
return MaterialApp(
home: Scaffold(
appBar: AppBar(
title: Text("FractionallySizedBox"),
),
body: myWidget(),
),
);
}
}
// replace with example code above
Widget myWidget() {
return ...
}
FractionallySizedBox constructor alignment parameter to Alignment.centerLeft, as the default is Alignment.center.
Sep 16, 2021 at 10:15
FractionallySizedBox, what is the reference used to calculate height or width factor, is it total screen size or something else
FractionallySizedBox may also be useful.
You can also read the screen width directly out of MediaQuery.of(context).size and create a sized box based on that
MediaQuery.of(context).size.width * 0.65
if you really want to size as a fraction of the screen regardless of what the layout is.
This might be a little more clear:
double width = MediaQuery.of(context).size.width;
double yourWidth = width * 0.65;
Hope this solved your problem.
There are several possibilities:
MediaQuery :Code :
MediaQuery.of(context).size.width //to get the width of screen
MediaQuery.of(context).size.height //to get height of screen
Example of use :
Container(
color: Colors.yellow,
height: MediaQuery.of(context).size.height * 0.65,
width: MediaQuery.of(context).size.width,
)
Output :
FractionallySizedBoxCreates a widget that sizes its child to a fraction of the total available space.
Example :
FractionallySizedBox(
widthFactor: 0.65, // between 0 and 1
heightFactor: 1.0,
child:Container(color: Colors.red
,),
)
Output :
Expanded , Flexible and AspectRatio and more .You could build a Column/Row with Flexible or Expanded children that have flex values that add up to the percentages you want.
You may also find the AspectRatio widget useful.
There is many way to do this.
1. Using MediaQuery : Its return fullscreen of your device including appbar,toolbar
Container(
width: MediaQuery.of(context).size.width * 0.50,
height: MediaQuery.of(context).size.height*0.50,
color: Colors.blueAccent[400],
)
2. Using Expanded : You can set width/height in ratio
Container(
height: MediaQuery.of(context).size.height * 0.50,
child: Row(
children: <Widget>[
Expanded(
flex: 70,
child: Container(
color: Colors.lightBlue[400],
),
),
Expanded(
flex: 30,
child: Container(
color: Colors.deepPurple[800],
),
)
],
),
)
3. Others Like Flexible and AspectRatio and FractionallySizedBox
First get the size of screen.
Size size = MediaQuery.of(context).size;
After this you can get width and multiply it with 0.5 to get 50% of screen width.
double width50 = size.width * 0.5;
But problem generally comes in height, by default when we use
double screenHeight = size.height;
The height we get is global height which includes StatusBar + notch + AppBar height. So, in order to get the left height of the device, we need to subtract padding height (StatusBar + notch) and AppBar height from total height. Here is how we do it.
double abovePadding = MediaQuery.of(context).padding.top;
double appBarHeight = appBar.preferredSize.height;
double leftHeight = screenHeight - abovePadding - appBarHeight;
Now we can use following to get 50% of our screen in height.
double height50 = leftHeight * 0.5
MediaQuery.of(context).size.width
you can use MediaQuery with the current context of your widget and get width or height like this
double width = MediaQuery.of(context).size.width
double height = MediaQuery.of(context).size.height
after that, you can multiply it with the percentage you want
Use the LayoutBuilder Widget that will give you constraints that you can use to obtain the height that excludes the AppBar and the padding. Then use a SizedBox and provide the width and height using the constraints from the LayoutBuilder
return LayoutBuilder(builder: (context2, constraints) {
return Column(
children: <Widget>[
SizedBox(
width: constraints.maxWidth,
height: constraints.maxHeight,
...
For width
double width = MediaQuery.of(context).size.width;
double yourWidth = width * 0.75;
For Height
double height = MediaQuery.of(context).size.height;
double yourHeight = height * 0.75;
If you don't want static height and width just use Expanded widget\
import 'package:flutter/material.dart';
void main() => runApp(const MyApp());
class MyApp extends StatelessWidget {
const MyApp({Key? key}) : super(key: key);
static const String _title = 'Flutter Code Sample';
@override
Widget build(BuildContext context) {
return const MaterialApp(
title: _title,
home: MyStatelessWidget(),
);
}
}
class MyStatelessWidget extends StatelessWidget {
const MyStatelessWidget({Key? key}) : super(key: key);
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: const Text('Expanded Row Sample'),
),
body: Center(
child: Row(
children: <Widget>[
Expanded(
flex: 2,
child: Container(
color: Colors.amber,
height: 100,
),
),
Container(
color: Colors.blue,
height: 100,
width: 50,
),
Expanded(
child: Container(
color: Colors.amber,
height: 100,
),
),
],
),
),
);
}
}
if you are using GridView you can use something like Ian Hickson's solution.
crossAxisCount: MediaQuery.of(context).size.width <= 400.0 ? 3 : MediaQuery.of(context).size.width >= 1000.0 ? 5 : 4
Code :
MediaQuery.of(context).size.width //to get the width of screen
MediaQuery.of(context).size.height //to get height of screen
You can use the Align widget. The heightFactor and widthFactor parameters are multiplied by the size of the child widget. Here is an example that will make a widget with a fixed height in% ratio
Align(
alignment: Alignment.topCenter,
heightFactor: 0.63,
widthFactor: ,
child: Container(
width: double.infinity,
),
Use scaler to define the layout width and height in percentage
dependencies:
scaler: ^1.1.0+1
After setting this in pubspec.yaml you can use this by following the code -
import 'package:scaler/scaler.dart';
Example After import use this -
import 'package:scaler/scaler.dart';
@override
Widget build(BuildContext context) {
/**
* Container with 25% width of screen
* and 25% height of screen
*/
return Container(
height: Scaler.height(0.25, context),
width: Scaler.width(0.25, context),
child: Container()
);
}
To more detail about this
I am surprised that no one has yet suggested LayoutBuilder in 2023 which gives you access to the parent's width BoxConstraints.constraints.maxWidth, which is the most versatile method.
Expanded can only set the percentage of the available spacing, but what if you really want to set a percentage based on the actual parent's widget only, not the entire screen width, what if have a fixed width widget in a row, even a more complex, what if you also want an Expanded to expand the remaining Row.
MediaQuery.of(context).size.width is relative to the entire screen, not to the actual parent.
FractionallySizedBox works similarly but you can't put it in Row
Also, this method the perfect emulation of CSS % unit of measurement.
class MyApp extends StatelessWidget {
const MyApp({Key? key}) : super(key: key);
@override
Widget build(BuildContext context) {
return LayoutBuilder(
builder: (context, BoxConstraints constraints) {
return SizedBox(
width: 470,
child: Row(
children: [
SizedBox(
width: 200,
child: Icon(
Icons.link,
color: Colors.white,
),
),
SizedBox(
width: constraints.maxWidth*0.6,
child: Icon(
Icons.message,
color: Colors.white,
),
),
Expanded(
child: Icon(
Icons.phone,
color: Colors.white,
),
),
SizedBox(
width: constraints.maxWidth*0.3,
child: Icon(
Icons.account_balance,
color: Colors.white,
),
),
],
),
);
}
);
}
}
In this example, we are setting a parent widget of 470 width with Row inside. In the Row, one element has a 200 fixed width, another with a 60% of the parent with 470, another with 30% of that same parent, and another expanding any remaining space.
Kindly use a very simple trick
Column( mainAxisAlignment: MainAxisAlignment.center, crossAxisAlignment: CrossAxisAlignment.stretch, )
Run this in the terminal
$ flutter pub add scaler
import this:
import 'package:scaler/scaler.dart';
then, this is an example:
import 'package:scaler/scaler.dart';
@override
Widget build(BuildContext context) {
/**
* Container with 25% width of screen
* and 25% height of screen
*/
return Container(
height: Scaler.height(0.25, context),
width: Scaler.width(0.25, context),
child: Container()
);
}
