If I created a widget, how can I set the width or height as screen ratio?
class HomeContent extends StatelessWidget{
#override
Widget build(BuildContext context) {
// TODO: implement build
return Center(
child: Container(
child: Image.network("http://a1.att.hudong.com/60/38/01200000194369136323385641912.jpg"),
width: 500,
height: 500,
decoration: BoxDecoration(
color: Colors.yellow,
),
),
);
}
}
You see my upper code, I want the width:Center_height as 1:2, how can I implement?
I mean the Center be carpeted with the screen page, the Container's height : Center's height = 1:2.
instead of directly passing value,
try using MediaQuery class.
Example
height: MediaQuery.of(context).size.height,
width: MediaQuery.of(context).size.width,
MediaQuery class will return the height / width of the current device, and you can directly use it accordingly, you can also use it like this,
width: MediaQuery.of(context).size.width / 2,
here, widget will occupy the half width available in current screen.
Use Mediaquery forheight and Width
height: MediaQuery.of(context).size.height,
width: MediaQuery.of(context).size.width,
And implement like this
class HomeContent extends StatelessWidget{
#override
Widget build(BuildContext context) {
// TODO: implement build
return Center(
child: Container(
child: Image.network("http://a1.att.hudong.com/60/38/01200000194369136323385641912.jpg"),
width: width,
height: height,
decoration: BoxDecoration(
color: Colors.yellow,
),
),
);
}
}
Related
When I nest two SizedBoxes, the width and height of the inner box are ignored. Why is this, how can I work around it?
import 'package:flutter/material.dart';
void main() {
runApp(MyApp());
}
class MyApp extends StatelessWidget {
#override
Widget build(BuildContext context) {
return Center(
child: SizedBox(
width: 300,
height: 500,
child: SizedBox(
width: 200, height: 200, child: Container(color: Colors.green)),
));
}
}
In this example, I have a 300x500 sized box and an inner 200x200 SizedBox. In the picture you can see that the green box is the size of the outer SizedBox but should actually be a 200x200 square.
According to flutter documentation: If given a child, this widget forces it to have a specific width and/or height. These values will be ignored if this widget's parent does not permit them. For example, this happens if the parent is the screen (forces the child to be the same size as the parent), or another SizedBox (forces its child to have a specific width and/or height). This can be remedied by wrapping the child SizedBox in a widget that does permit it to be any size up to the size of the parent, such as Center or Align.
So wrapping the child with center would solve the problem:
Center(
child: SizedBox(
width: 300,
height: 500,
child: Center(
child: SizedBox(
width: 200, height: 200, child: Container(color: Colors.green)),
),
)),
The problem is, SizedBox can set widget size only within the constrains set by the parent. Many widgets, like Padding, want their child to occupy 100% of the space available to them. This makes sense, because if the child is smaller they wouldn't know where to put it.
If you want the child to be smaller than the parent you could use Center or Align, e.g. replace
I had the same issue and I solved my problem using the FractionallySizedBox class.
You can specify the suitable size using fractions of the above SizedBox as widthFactor and heightFactor:
Widget build(BuildContext context) {
return SizedBox.expand(
child: FractionallySizedBox(
widthFactor: 0.5,
heightFactor: 0.5,
alignment: FractionalOffset.center,
child: DecoratedBox(
decoration: BoxDecoration(
border: Border.all(
color: Colors.blue,
width: 4),
),
),
),
);
}
The following Flutter widget build will show an image on the screen:
#override
Widget build(BuildContext context) {
return Image.asset('assets/images/image.jpg');
}
How do I wrap or configure the Image in order to show a zoomed/scaled version that is allowed to overflow the screen boundaries. Nothing I have tried so far has worked. I would like to set the image to a width of 1.25 times the screen width and then present it as illustrated below.
Wrapping the image in a FittedBox and specifying fit: BoxFit.cover along with setting both width and height for the image will make it work.
#override
Widget build(BuildContext context) {
return FittedBox(
child: Image.asset(
'assets/images/image.jpg',
width: MediaQuery.of(context).size.width * 1.25,
height: 400,
fit: BoxFit.cover,
),
);
}
I think that something like this could be what you are looking for.
Basically giving the width of the image based on your screen size, it is important to notice that it will scale with the screen size, so a tablet might be a problem with respect to a mobile phone
#override
Widget build(BuildContext context) {
Size size = MediaQuery.of(context).size;
return ClipRect(
clipBehavior: Clip.hardEdge,
child: Image.asset(
'assets/images/image.jpg',
width: size.width * 1.25,
fit: BoxFit.cover
),
);
}
EDIT: I've tried to run the code myself and it looks like the best solution for this is a Stack, below the code
#override
Widget build(BuildContext context) {
Size size = MediaQuery.of(context).size;
return Stack(children: [
Positioned(
left: -size.width*0.125,
right: -size.width*0.125,
child: Image.asset(
'assets/images/image.jpg',
),
),
]
);
}
import 'package:flutter/material.dart';
void main() => runApp(MyApp());
class MyApp extends StatelessWidget {
#override
Widget build(BuildContext context) {
return MaterialApp(
title: 'Flutter Demo',
home: TestCode(),
);
}
}
class TestCode extends StatelessWidget {
#override
Widget build(BuildContext context) {
return Container(
width: 200,
height: 100,
color: Colors.red,
child: Container(
width: 100,
height: 100,
color: Colors.green,
),
);
}
}
In fact, this code is very simple. I just want to display a 200 * 100 red cube and a 100 * 100 green cube.
But the running effect is full screen green? Why is that?
Next, I added a Scaffold toTestCode, as follows
#override
Widget build(BuildContext context) {
return MaterialApp(
title: 'Flutter Demo',
home: Scaffold(body: TestCode()),
);
}
The effect again seems to be closer, showing a 200 * 100 green cuboid? Why is that?
Next, I added an alignment to the first Container, as follows
#override
Widget build(BuildContext context) {
return Container(
alignment: Alignment.topLeft,
width: 200,
height: 100,
color: Colors.red,
child: Container(
width: 100,
height: 100,
color: Colors.green,
),
);
}
Finally achieved the desired effect, why is this, who can explain, I must figure this out.
This is caused by what we call "tight vs loose constraints" in Flutter.
TD;DR, width/height are tight constraints (in the sense that there's only a single possibility).
But you never specified to the framework how to switch between the tight constraint of 200x200 specified by the parent, to the tight constraint of 100x100 of the child.
This cause a constraint conflict. Both widgets have a single possibility, and there's nothing that allows both to live together (like an alignment).
In that situation, the constraints of the parent always win, and we therefore end up with a 200x200 square where the child fills its parent.
If that is not what you want; then you should transform your "tight" constraint into a "loose" constraint.
A loose constraint is a constraint that offer the child multiple possibilities, which usually remove the conflict.
The most common way to introduce a loose constraint is to use Alignment (or Center or the alignment property of Container).
As such, if you write:
Container(
width: 200,
height: 100,
color: Colors.red,
child: Center(
child: Container(
width: 100,
height: 100,
color: Colors.green,
),
),
);
then in that situation, Center will act as a middle ground between the parent and child Container.
It will understand that both wants a different size. And it will solve the conflict by aligning the child in the parent.
Now, why is this desired you may ask? Why can't Flutter implicitly add an alignment here?
That is because in many situations, this behavior is desired.
Basically, this ensures that there's always a way to customize the size of something (without having to expose tons of properties on all widgets).
Take RaisedButton as an example. It doesn't expose anything to change its size, but we may want it to fill the screen.
In that situation we'd write:
SizedBox.expand(
child: RaisedButton(...),
)
Because of the behavior we explained previously with the parent overriding the child size when there's a conflict, this code will produce a RaisedButton that properly fills the screen.
height and width properties getting overrided. You can have more info about box constraints on this article:
Dealing with box constraints
Flutter has bunch of layout widgets that can get the job done. In your case you gave Container to the home property of MaterialApp. This set the minimum size of the Container to the screen size. MaterialApp wants his child to fill all the screen in order to prevent any black pixels. This is an expected behaviour. However you can use a layout widget that can break this constraint, it may be Center , FittedBox or else.
An example with FittedBox:
class TestCode extends StatelessWidget {
#override
Widget build(BuildContext context) {
return FittedBox(
fit: BoxFit.scaleDown,
child: Container(
width: 200,
height: 100,
color: Colors.red,
child: FittedBox(
fit: BoxFit.scaleDown,
child: Container(
width: 100,
height: 100,
color: Colors.green,
),
),
),
);
}
}
Output:
Always remember that the container by default takes the dimensions of the parent, and it's a good practice to wrap all your elements/widgets in a root top level Container and then wrap each container in the widget tree with widgets that position the desired Container (Center can be such a widget)
An easy work-around solution for your problem would be:
// The root container
Container(
//Center for positioning the child Container properly
child: Center(
child: Container(
height: 100,
width: 200,
color: Colors.red,
//Center for positioning the child Container properly
child: Center(
child: Container(
height: 100,
width: 100,
color: Colors.green,
),
),
),
),
),
Just change your code into this. You have to specify alignment.
import 'package:flutter/material.dart';
void main() => runApp(MyApp());
class MyApp extends StatelessWidget {
#override
Widget build(BuildContext context) {
return MaterialApp(
title: 'Flutter Demo',
home: TestCode(),
);
}
}
class TestCode extends StatelessWidget {
#override
Widget build(BuildContext context) {
return Container(
width: 200.0,
height: 100.0,
color: Colors.red,
alignment: Alignment.center, // where to position the child
child: Container(
width: 100.0,
height: 100.0,
color: Colors.green,
),
);
}
}
Please see this image -https://ibb.co/YpjJsLZ
In above image how can I place burger image to center of white view.
I tried using Align & Center widget but its no fitting properly.
How can relative layout works in flutter?
Flutter does not have layout types like android,
But you can place burger image using stack widget.
You can follow this tutorial for reference.
you can not use Relative Layout in Flutter but it Replace using "Stack".
The stack is a widget in Flutter that contains a list of widgets and positions them on top of the other.
stack allows developers to overlap multiple widgets into a single screen and renders them from bottom to top.
Hence, the first widget is the bottommost item, and the last widget is the topmost item.
import 'package:flutter/material.dart';
class StackWidget extends StatefulWidget {
#override
_StackWidgetState createState() => _StackWidgetState();
}
class _StackWidgetState extends State<StackWidget> {
#override
Widget build(BuildContext context) {
return Container(
width: double.infinity,
color: Colors.yellow,
height: 300,
child: Stack(
alignment: Alignment.topLeft,
children: [
Container(
color: Colors.cyan,
width: 200,
height: 200,
),
Container(
color: Colors.red,
width: 150,
height: 150,
),
Container(
color: Colors.blue,
width: 100,
height: 100,
),
],
),
);
}
}
Output:
Done☻♥.
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.
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.
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.
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 ...
}
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:
1- The first one is the use of the 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 :
2- The use of FractionallySizedBox
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 :
3- The use of other widgets such as 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,
...
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
https://pub.dev/packages/scaler
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,
),
),
],
),
),
);
}
}
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.