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I'm creating a listview widget and i want it to have varying container sizes that change from user inputs inside it, the problem is when i wrap my columns or rows in expanded widgets, the code breaks.
is there a way to set a min and max height for a list view widget?
ListView(
children: [
Column(
children: [
Row(
children: [
Expanded(
child: Container(
color: Colors.yellow,
),
),
Container(
width: 2,
color: kKillTeamOrange,
),
Expanded(
child: Container(
color: Colors.green,
),
),
],
),
],
),
],
),
I tried wrapping the listview in a constrained container but no luck, the other option would be to have the buttons set the height state but there are a lot of buttons to code that. and using expanded widgets is great for varying screen sizes.
any help would be greatly appreciated.
cheers
Two ways came to mind:
CustomScrollView
ListView (But using cards)
Both ways are responsive to screen sizes
LISTVIEW WITH CARD:
CUSTOM SCROLLVIEW:
RESULT:
hope this helps...
In iOS's native AutoLayout constraints, It very easy to make a equal width constraints between ViewA and ViewB . And these two views will get a same width always.
But in flutter ,it seems can't be achived this kindof constraints so easily?
Do I have to make a SizedBox with specific width for both WidgetA and WidgetB explicitly?
You can always put your widgets in a Row(), and wrap every widget in Expanded(). This way they will always have 50% width of the parent Row(). And if you need to constrain the width, just wrap the Row() in a SizedBox().
SizedBox(
width: 500.0,
child: Row(
children: [
Expanded(
child: Container(),
),
Expanded(
child: Container(),
),
],
),
),
As far as I see, Column and ListView both have a very distinct usage when used for a base root layouting.
Column is used when the screen has few components (such as login screen). We can add some Expanded components to adjust white spaces in between, so when the keyboard is visible, the screen shrink to keep everything visible.
ListView is used when the screen has many components that potentially need scrolling. We can't use Expanded component in ListView. When using ListView, appearing keyboard does not change the white spaces, only change the size of outer ListView, while the inner content is wrapped in scroll view.
Now the problem is, how if I want to have screen like this:
When all the contents' combined vertical size is not longer than available height quota given from parent (in this case, screen's height), then the components behave like inside Column: expanding or shrinking to fill available white spaces according to rules set by Expanded.
When all the content's combined vertical size is longer than available height quota, then the components behave like inside ListView: all the possible expanding components will shrink into their minimum size (ignoring Expanded), and the screen is scrollable so user can see the rest of the screen below.
Is this possible to be done in Flutter? How?
EDIT: based on Reign's comment, I have isolated some code from SingleChildScrollView manual, but it looks like it still can't handle if its children contains Expanded.
Widget columnRoot({
MainAxisAlignment mainAxisAlignment = MainAxisAlignment.spaceBetween,
AssetImage backgroundImage,
List<Widget> children
}) =>
LayoutBuilder(builder: (BuildContext context, BoxConstraints viewportConstraints) =>
SingleChildScrollView(
child: ConstrainedBox(
constraints: BoxConstraints(
minHeight: viewportConstraints.maxHeight,
),
child: Container(
decoration: BoxDecoration(
image: DecorationImage(
image: backgroundImage,
fit: BoxFit.cover),
color: Colors.white
),
child: Column(
mainAxisSize: MainAxisSize.min,
mainAxisAlignment: mainAxisAlignment,
children: children
),
)
)
)
);
Widget content(BuildContext context) => columnRoot(children: [
Container(color: Colors.red, height: 100.0),
Expanded(Container(color: Colors.green)), // without this line, there's no layout error
Container(color: Colors.blue, height: 100.0),
]);
Error:
RenderFlex children have non-zero flex but incoming height constraints are unbounded.
I added some code you can test with also with some explanation.
Copy paste and run the code
class MyWidget extends StatelessWidget {
#override
Widget build(BuildContext context) {
return Scaffold(
body: Container(
child: SingleChildScrollView( //Since setting it to scrollable, your widget Column with expanded children wont work as it supposed to be because it wont know its parent height
//Since its already scrollable `Expanded` will expand or shrink now based on it child widget (Expanded(child: SomeHeight widget)) refer: #10 example
child: IntrinsicHeight( //This will fix the expanded widget error
child: Container(
//Test remove this height
// height: 400, //But when you set its height before its parent scroll widget, `Expanded` will expand based on its available space
child: Column(
crossAxisAlignment: CrossAxisAlignment.stretch,
mainAxisSize: MainAxisSize.max,
children: [
Container(color: Colors.red, height: 100.0),
//#10
//Experiment with this
Expanded(
child: Container(
color: Colors.purple,
// height: 100.0, //initialized height, remove parent container height: 400
// child: Text("This is also considered as min height"),
),
),
Container(color: Colors.blue, height: 100.0),
],
),
),
),
),
),
);
}
}
TL;DR Need the container to fill the vertical space so that it can act as a ontap listener. Have tried most solutions but nothing seems to work.
So what I am trying to do is to make my container fill up the vertical space while still having a fixed width. Two first is what I have and third is what I want. The idea is to have the container transparent with a gesture ontap listener. If anyone have a better idea as for a different solution, feel free to suggest.
Widget build(BuildContext context) {
return new GestureDetector(
onHorizontalDragUpdate: _move,
onHorizontalDragEnd: _handleDragEnd,
child: new Stack(
children: <Widget>[
new Positioned.fill(
child: new Row(
mainAxisAlignment: MainAxisAlignment.end,
children: <Widget>[
new Container(
child: new IconButton(
padding: new EdgeInsets.only(top: 16.0, bottom: 16.0, left: 24.0, right: 24.0),
icon: new Icon(Icons.warning),
color: Colors.black12,
onPressed: () {},
)
),
],
),
),
new SlideTransition(
position: new Tween<Offset>(
begin: Offset(0.0, 0.0),
end: const Offset(-0.6, 0.0),
).animate(_animation),
child: new Card(
child: new Row(
children: <Widget>[
new Container(
width: 20.0,
height: 20.0,
color: Colors.amber,
),
new Expanded(
child: new Column(
mainAxisSize: MainAxisSize.min,
children: <Widget>[
_getListTile(),
_ifStoplineIsToBeShown()
],
),
)
],
)
),
),
],
)
);
}
I am quite sure that i have been missing something considering the fact that I have tried a lot of different things and nothing seems to work.
I have also uploaded an image with the debug painting here.
PS. I know I have set the height to a fixed value, but this is the only way to show the container.
The trick is to combine an IntrinsicHeight widget and a Row with crossAxisAlignment: CrossAxisAlignment.stretch
This force the children of Row to expand vertically, but Row will take the least amount of vertical space possible.
Card(
child: IntrinsicHeight(
child: Row(
crossAxisAlignment: CrossAxisAlignment.stretch,
children: <Widget>[
Container(
width: 20.0,
color: Colors.amber,
),
// Expanded(...)
],
),
)
)
To stretch the container to full height of the parent use property constraints:BoxConstraints.expand() in container widget. Container occupy the complete space independent of the of child widget
Container(
color: Colors.green,
child: Text("Flutter"),
constraints: BoxConstraints.expand(),
)
Please refer the link Container Cheat sheet for more about container
Simply pass in: double.infinity.
If you want a Container to fill all available space, you can just pass in:
width: double.infinity,
height: double.infinity
Explanation:
In Flutter, a child widget cannot exceed the "layout constraints" imposed by its parent widget. During the layout phase, Flutter engine uses a constraint solver to automatically correct "out-of-bound" values into what's allowed by its parent constraints.
For example, if you have a Container that's 50x50, and for its child, you pass in another Container that's 300x300, the inner container will be automatically corrected to "not exceed its parent", thus 50x50. Therefore, using sufficiently large values would always make sure you "fill parent".
In fact, even BoxConstraints.expand() exploits the same idea internally. If you open up the source code of expand(), you will see:
/// Creates box constraints that expand to fill another box constraints.
///
/// If width or height is given, the constraints will require exactly the
/// given value in the given dimension.
const BoxConstraints.expand({
double width,
double height,
}) : minWidth = width ?? double.infinity,
maxWidth = width ?? double.infinity,
minHeight = height ?? double.infinity,
maxHeight = height ?? double.infinity;
So if you are absolutely certain you want to fill all spaces, you can intuitively pass in a number bigger than the parent (or larger than the whole screen), like double.infinity.
As of Jan 2020 the simplest is to use an Expanded Widget
Expanded(flex: 1,
child: Container(..),
),
https://api.flutter.dev/flutter/widgets/Expanded-class.html
There are many answers which suggest using two things
constraints: BoxConstraints.expand(),
height: double.infinity,
But both these answer will give you an error like
BoxConstraints forces an infinite height.
We can avoid these by calculating the height of the screen like
App Bar
Top Bar Space(Exist on the above App Bar)
Remaining screen
1. Get the MediaQuery
final mediaQuery = MediaQuery.of(context);
2. Declare the AppBar Widget and same App Bar instance should be used in Scaffold App Bar
final PreferredSizeWidget appBar = AppBar(
title: Text('Home'),
);
3. Use calculated height
Container(
width: mediaQuery.size.width,
height: (mediaQuery.size.height -
appBar.preferredSize.height -
mediaQuery.padding.top),
color: Colors.red,
),
Output:
Set the height or width of a container to double.maxFinite
Container(
height: double.maxFinite,
width: 100,)
You can make your widget take the full size of a Container widget, and then set the container's height and/or width to double.maxFinite. This will make the Container take the height and/or width or its parent widget
I propose using Expanded widget (which allows us to avoid IntrinsicHeight widget), combine it with the Container's alignment property and therefore make it work properly even if the Container is not the only one at the screen.
Expanded(
child: Container(
alignment: Alignment.center,
child: Text('Your text', textAlign: TextAlign.center))),
That way one also avoids potential app's crash which occurs often when you accidentally expand to infinity some parts of the widget tree both horizontally and vertically (that is why you are not able to use BoxConstraints widget in many cases).
One can read more about the problems of passing constraints in Flutter here - a must read: https://medium.com/flutter-community/flutter-the-advanced-layout-rule-even-beginners-must-know-edc9516d1a2
This work works for me
height: MediaQuery.of(context).size.height,
In Android match_parent and wrap_content are used to resize the widgets automatically relative to their parent to the content the widget contains.
In Flutter it seems by default all widgets are set to wrap_content, how would I change it such that I can fill its width and height to that of its parent?
You can do with little Trick:
Suppose you have requirement of :
( Width,Height )
Wrap_content ,Wrap_content :
//use this as child
Wrap(
children: <Widget>[*your_child*])
Match_parent,Match_parent:
//use this as child
Container(
height: double.infinity,
width: double.infinity,child:*your_child*)
Match_parent,Wrap_content :
//use this as child
Row(
mainAxisSize: MainAxisSize.max,
children: <Widget>[*your_child*],
);
Wrap_content ,Match_parent:
//use this as child
Column(
mainAxisSize: MainAxisSize.max,
children: <Widget>[your_child],
);
In order to get behavior for match_parent and wrap_content we need to
use mainAxisSize property in Row/Column widget, the mainAxisSize
property takes MainAxisSize enum having two values which is
MainAxisSize.min which behaves as wrap_content and MainAxisSize.max
which behaves as match_parent.
Link of the original Article
The short answer is that the parent doesn't have a size until the child has a size.
The way layout works in Flutter is that each widget provides constraints to each of its children, like "you can be up to this wide, you must be this tall, you have to be at least this wide", or whatever (specifically, they get a minimum width, a maximum width, a minimum height, and a maximum height). Each child takes those constraints, does something, and picks a size (width and height) that matches those constraints. Then, once each child has done its thing, the widget can can pick its own size.
Some widgets try to be as big as the parent allows. Some widgets try to be as small as the parent allows. Some widgets try to match a certain "natural" size (e.g. text, images).
Some widgets tell their children they can be any size they want. Some give their children the same constraints that they got from their parent.
There are actually some options available:
You can use SizedBox.expand to make your widget match parents dimensions, or SizedBox(width: double.infinity) to match only the width or SizedBox(heigth: double.infinity) to match only the heigth.
If you want a wrap_content behavior it depends on the parent widget you are using, for example if you put a button on a column it will behave like wrap_content and to use it like match_parent you can wrap the button with a Expanded widget or a sizedbox.
With a ListView the button gets a match_parent behavior and to get a wrap_content behavior you can wrap it with a Flex widget like Row.
Using an Expanded widget makes a child of a Row, Column, or Flex
expand to fill the available space in the main axis (e.g., horizontally for
a Row or vertically for a Column).
https://docs.flutter.io/flutter/widgets/Expanded-class.html
Using a Flexible widget gives a child of a Row, Column, or Flex the flexibility to expand to fill the available space in the main axis (e.g., horizontally for a Row or vertically for a Column), but, unlike Expanded, Flexible does not require the child to fill the available space.
https://docs.flutter.io/flutter/widgets/Flexible-class.html
Use the widget Wrap.
For Column like behavior try:
return Wrap(
direction: Axis.vertical,
spacing: 10,
children: <Widget>[...],);
For Row like behavior try:
return Wrap(
direction: Axis.horizontal,
spacing: 10,
children: <Widget>[...],);
For more information: Wrap (Flutter Widget)
I used this solution, you have to define the height and width of your screen using MediaQuery:
Container(
height: MediaQuery.of(context).size.height,
width: MediaQuery.of(context).size.width
)
To make a child fill its parent, simply wrap it into a FittedBox
FittedBox(
child: Image.asset('foo.png'),
fit: BoxFit.fill,
)
A simple workaround:
If a container has only one top level child, then you can specify alignment property for the child and give it any available value. it'll fill all the space in the container.
Container(color:Colors.white,height:200.0,width:200.0,
child:Container(
color: Colors.yellow,
alignment:Alignment.[any_available_option] // make the yellow child match the parent size
)
)
Another way:
Container(color:Colors.white,height:200.0,width:200.0,
child:Container(
color: Colors.yellow,
constraints: BoxConstraints.expand(height: 100.0), // height will be 100 dip and width will be match parent
)
)
Stack(
children: [
Container(color:Colors.red, height:200.0, width:200.0),
Positioned.fill(
child: Container(color: Colors. yellow),
)
]
),
Use FractionallySizedBox widget.
FractionallySizedBox(
widthFactor: 1.0, // width w.r.t to parent
heightFactor: 1.0, // height w.r.t to parent
child: *Your Child Here*
}
This widget is also very useful when you want to size your child at a fraction of its parent's size.
Example:
If you want the child to occupy 50% width of its parent, provide widthFactor as 0.5
Match Parent
To match or fill the parent (height & width) we can use additional constraints on Container:
Container(
constraints: BoxConstraints.expand(), // ← this guy
child: Text('Center > Container > Text')
)
In Flutter, constraints are the space you can fill (or must fill, if "tight" constraints).
Constraints are given... no actually, imposed by parents.
By default, Container will wrap its content (child:) & size itself to its child, unless overriden (or not allowed by tight constraints).
Using the constraints: argument, we can give Container additional constraints to override default Container constraint behavior (such as wrapping content).
Using Container(constraints: BoxConstraints.something) doesn't overwrite incoming/parent constraints; It just allows us to override default behavior, where allowed, such as wrapping content.
Code Sample - BoxConstraints
Here's a copy/paste code example showing effects of various constraints we can apply to a Container that has "loose" incoming/parental constraints (provided by Center).
import 'package:flutter/material.dart';
class MatchParentPage extends StatefulWidget {
#override
_MatchParentPageState createState() => _MatchParentPageState();
}
class _MatchParentPageState extends State<MatchParentPage> {
BoxConstraints constraints;
#override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text('Match Parent'),
),
body: Column(
mainAxisAlignment: MainAxisAlignment.spaceEvenly,
children: [
Expanded( // shares space constraint evenly with other Expanded
child: Center( // ← fills tight parent constraint & loosens ↓ child constraint ↓
child: Container( // got loose constraint from Center...
constraints: constraints, // can apply many additional constraints
color: Colors.lightBlueAccent.withOpacity(.3),
child: Text('Center > Container > Text')),
),
),
Expanded(
child: Container(
color: Colors.orangeAccent,
child: Wrap(
children: [
_button('default', null),
_button('*expand()', BoxConstraints.expand()),
_button('*tight(Size.infinite)', BoxConstraints.tight(Size.infinite)),
_button('tight(Size.zero)', BoxConstraints.tight(Size.zero)),
_button('tight(Size.fromHeight(100))', BoxConstraints.tight(Size.fromHeight(100))),
_button('tight(Size.fromWidth(100))', BoxConstraints.tight(Size.fromWidth(100))),
_button('tightForFinite(width: 100, height: 100)', BoxConstraints.tightForFinite(width: 100, height: 100)),
_button('loose(Size.infinite)', BoxConstraints.loose(Size.infinite)),
_button('tightFor(width: double.infinity)', BoxConstraints.tightFor(width: double.infinity)),
_button('tightFor(height: double.infinity)', BoxConstraints.tightFor(height: double.infinity)),
])
),
)
],
),
);
}
Widget _button(String label, BoxConstraints _constraints) {
bool _active = _constraints == constraints;
return Padding(
padding: const EdgeInsets.only(top:8, left: 8),
child: RaisedButton(
color: _active ? Colors.cyanAccent : null,
child: Text(label),
onPressed: () {
setState(() => constraints = _constraints);
},
),
);
}
}
Use this line of codes inside the Column.
For wrap_content : mainAxisSize: MainAxisSize.min
For match_parent : mainAxisSize: MainAxisSize.max
MATCH_PARENT
FractionallySizedBox(
widthFactor: 1.0, // width w.r.t to parent
heightFactor: 1.0, // height w.r.t to parent
child: ElevatedButton(
onPressed: () {},
child: Text("+"),
),
)
OR
Container(
height: double.infinity,
width: double.infinity,
child: ElevatedButton(
onPressed: () {},
child: Text("+"),
),
)
OR
Container(
height: MediaQuery.of(context).size.height,
width: MediaQuery.of(context).size.width,
child: ElevatedButton(
onPressed: () {},
child: Text("+"),
),
)
OR
Container(
constraints: BoxConstraints.expand(),
child: ElevatedButton(
onPressed: () {},
child: Text("+"),
),
)
WRAP_CONTENT
Wrap(children: [
Container(
child: ElevatedButton(
onPressed: () {},
child: Text("+"),
),
),
])
OR
Container(
constraints: BoxConstraints.tightFor(),
child: ElevatedButton(
onPressed: () {},
child: Text("+"),
),
)
Match_parent,Wrap_content :
Row(
children: [
Expanded(
child: Container(
child: ElevatedButton(
onPressed: () {},
child: Text("+"),
),
),
),
])
Wrap_content,Match_parent :
Column(
children: [
Expanded(
child: Container(
child: ElevatedButton(
onPressed: () {},
child: Text("+"),
),
),
),
])
For match parent option you can wrap your widget by a container and give it a width like this
width: double.infinity
this approach will make the widget fill max space available for it on the screen.