Sizing elements to percentage of screen width/height
FlutterDartFlutter LayoutScreen SizeFlutter Problem Overview
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?
Flutter Solutions
Solution 1 - Flutter
This is a supplemental answer showing the implementation of a couple of the solutions mentioned.
FractionallySizedBox
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.
https://i.stack.imgur.com/LRSc5.png" width="300" alt="FractionallySizedBox">
Widget myWidget() {
return FractionallySizedBox(
widthFactor: 0.7,
heightFactor: 0.3,
child: Container(
color: Colors.green,
),
);
}
Expanded
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.
https://i.stack.imgur.com/cY4AS.png" width="300" alt="Expanded">
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,
),
),
],
);
}
Supplemental code
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 ...
}
Solution 2 - Flutter
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.
Solution 3 - Flutter
This might be a little more clear:
double width = MediaQuery.of(context).size.width;
double yourWidth = width * 0.65;
Hope this solved your problem.
Solution 4 - Flutter
There are several possibilities:
MediaQuery
:
1- The first one is the use of the 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 :
FractionallySizedBox
2- The use of Creates 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 .
3- The use of other widgets such as Solution 5 - Flutter
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.
Solution 6 - Flutter
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
Solution 7 - Flutter
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
Solution 8 - Flutter
MediaQuery.of(context).size.width
Solution 9 - Flutter
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
Solution 10 - Flutter
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,
...
Solution 11 - Flutter
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
Solution 12 - Flutter
Code :
MediaQuery.of(context).size.width //to get the width of screen
MediaQuery.of(context).size.height //to get height of screen
Solution 13 - Flutter
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,
),