How to use Expanded in SingleChildScrollView?
FlutterFlutter Problem Overview
How to use Expanded in SingleChildScrollView? I have a screen with Image.network, ListView.builder and Row (TextFormField and IconButton). I wrapped ListView with Expanded. How to wrap this column with SingleChildScrollView? I need to move screen when the keyboard is open to see what I am writing. When I wrap my column I have this error.
body: SingleChildScrollView(
child: Column(
children: <Widget>[
Container(
child: GestureDetector(
child:
Image.network(
postOne.imageUrl,
fit: BoxFit.fitWidth,
height: MediaQuery
.of(context)
.size
.width,
width: MediaQuery
.of(context)
.size
.width,
),
onLongPress: () {},
onDoubleTap: () {},
),
),
Expanded(
//height: MediaQuery.of(context).size.width*0.33,
child: ListView.builder(
itemCount: commentList.length,
itemBuilder: (context, position) {
return GestureDetector(
onLongPress: () {},
child: Card(
child: Padding(
padding: EdgeInsets.all(5.0),
child: new CheckboxListTile(
title: new Text(commentList
.elementAt(position)
.coment,
style: TextStyle(fontSize: 18.0),),
value: values[commentList
.elementAt(position)
.coment],
onChanged: (bool value) {}),
),
)
);
}
),
),
Container(
child: Row(
crossAxisAlignment: CrossAxisAlignment.start,
children: [
new Flexible(
child: Theme(
data: new ThemeData(
brightness: Brightness.light,
primarySwatch: Colors.grey,
inputDecorationTheme: new InputDecorationTheme(
labelStyle: new TextStyle(
color: Colors.black45, fontSize: 18.0
),
)
),
child: new Form(
key: _formKey,
child: new TextFormField(
validator: (value) {
if (value.isEmpty) {
return 'Please enter the comment';
}
},
controller: commentController,
decoration: new InputDecoration(
labelText: "Add comment",
//hintText: 'Add comment'
),
keyboardType: TextInputType.text,
),
),
),
),
new Container(
margin: EdgeInsets.only(left: 10.0, top: 12.0),
child: new IconButton(
icon: new Icon(Icons.send, color: Colors.black,),
onPressed: () {}
)
),
]),
),
],
),
),
I/flutter ( 6816): ══╡ EXCEPTION CAUGHT BY RENDERING LIBRARY ╞═════════════════════════════════════════════════════════
I/flutter ( 6816): The following assertion was thrown during performLayout():
I/flutter ( 6816): RenderFlex children have non-zero flex but incoming height constraints are unbounded.
I/flutter ( 6816): When a column is in a parent that does not provide a finite height constraint, for example if it is
I/flutter ( 6816): in a vertical scrollable, it will try to shrink-wrap its children along the vertical axis. Setting a
I/flutter ( 6816): flex on a child (e.g. using Expanded) indicates that the child is to expand to fill the remaining
I/flutter ( 6816): space in the vertical direction.
I/flutter ( 6816): These two directives are mutually exclusive. If a parent is to shrink-wrap its child, the child
I/flutter ( 6816): cannot simultaneously expand to fit its parent.
I/flutter ( 6816): Consider setting mainAxisSize to MainAxisSize.min and using FlexFit.loose fits for the flexible
I/flutter ( 6816): children (using Flexible rather than Expanded). This will allow the flexible children to size
I/flutter ( 6816): themselves to less than the infinite remaining space they would otherwise be forced to take, and
I/flutter ( 6816): then will cause the RenderFlex to shrink-wrap the children rather than expanding to fit the maximum
I/flutter ( 6816): constraints provided by the parent.
I/flutter ( 6816): The affected RenderFlex is:
I/flutter ( 6816): RenderFlex#9f534 relayoutBoundary=up11 NEEDS-LAYOUT NEEDS-PAINT
I/flutter ( 6816): The creator information is set to:
I/flutter ( 6816): Column ← _SingleChildViewport ← IgnorePointer-[GlobalKey#3670d] ← Semantics ← Listener ←
I/flutter ( 6816): _GestureSemantics ← RawGestureDetector-[LabeledGlobalKey<RawGestureDetectorState>#4878e] ←
I/flutter ( 6816): Listener ← _ScrollableScope ← _ScrollSemantics-[GlobalKey#c5885] ← RepaintBoundary ← CustomPaint ←
I/flutter ( 6816): ⋯
I/flutter ( 6816): The nearest ancestor providing an unbounded width constraint is:
I/flutter ( 6816): _RenderSingleChildViewport#155d8 relayoutBoundary=up10 NEEDS-LAYOUT NEEDS-PAINT
I/flutter ( 6816): creator: _SingleChildViewport ← IgnorePointer-[GlobalKey#3670d] ← Semantics ← Listener ←
I/flutter ( 6816): _GestureSemantics ← RawGestureDetector-[LabeledGlobalKey<RawGestureDetectorState>#4878e] ←
I/flutter ( 6816): Listener ← _ScrollableScope ← _ScrollSemantics-[GlobalKey#c5885] ← RepaintBoundary ← CustomPaint ←
I/flutter ( 6816): RepaintBoundary ← ⋯
I/flutter ( 6816): parentData: <none> (can use size)
I/flutter ( 6816): constraints: BoxConstraints(0.0<=w<=440.8, 0.0<=h<=649.3)
I/flutter ( 6816): size: MISSING
I/flutter ( 6816): See also: https://flutter.dev/layout/
I/flutter ( 6816): If this message did not help you determine the problem, consider using debugDumpRenderTree():
I/flutter ( 6816): https://flutter.dev/debugging/#rendering-layer
I/flutter ( 6816): http://docs.flutter.io/flutter/rendering/debugDumpRenderTree.html
I/flutter ( 6816): If none of the above helps enough to fix this problem, please don't hesitate to file a bug:
I/flutter ( 6816): https://github.com/flutter/flutter/issues/new?template=BUG.md
I/flutter ( 6816):
Flutter Solutions
Solution 1 - Flutter
Instead of using SingleChildScrollView, It's easier to use CustomScrollView with a SliverFillRemaining.
Try this:
CustomScrollView(
slivers: [
SliverFillRemaining(
hasScrollBody: false,
child: Column(
children: <Widget>[
const Text('Header'),
Expanded(child: Container(color: Colors.red)),
const Text('Footer'),
],
),
),
],
)
Solution 2 - Flutter
Try this,
LayoutBuilder(
builder: (context, constraint) {
return SingleChildScrollView(
child: ConstrainedBox(
constraints: BoxConstraints(minHeight: constraint.maxHeight),
child: IntrinsicHeight(
child: Column(
children: <Widget>[
Text("Header"),
Expanded(
child: Container(
color: Colors.red,
),
),
Text("Footer"),
],
),
),
),
);
},
)
I got this solution from git issues when I get into the same situation. I don't have the git link. I think it may help you.
Reusable widget:
Note: use it, only if one of the children is Expanded
import 'package:flutter/material.dart';
class ScrollColumnExpandable extends StatelessWidget {
final List<Widget> children;
final CrossAxisAlignment crossAxisAlignment;
final MainAxisAlignment mainAxisAlignment;
final VerticalDirection verticalDirection;
final TextDirection textDirection;
final TextBaseline textBaseline;
final EdgeInsetsGeometry padding;
const ScrollColumnExpandable({
Key key,
this.children,
CrossAxisAlignment crossAxisAlignment,
MainAxisAlignment mainAxisAlignment,
VerticalDirection verticalDirection,
EdgeInsetsGeometry padding,
this.textDirection,
this.textBaseline,
}) : crossAxisAlignment = crossAxisAlignment ?? CrossAxisAlignment.center,
mainAxisAlignment = mainAxisAlignment ?? MainAxisAlignment.start,
verticalDirection = verticalDirection ?? VerticalDirection.down,
padding = padding ?? EdgeInsets.zero,
super(key: key);
@override
Widget build(BuildContext context) {
final children = <Widget>[const SizedBox(width: double.infinity)];
if (this.children != null) children.addAll(this.children);
return LayoutBuilder(
builder: (context, constraint) {
return SingleChildScrollView(
child: Padding(
padding: padding,
child: ConstrainedBox(
constraints: BoxConstraints(
minHeight: constraint.maxHeight - padding.vertical,
),
child: IntrinsicHeight(
child: Column(
crossAxisAlignment: crossAxisAlignment,
mainAxisAlignment: mainAxisAlignment,
mainAxisSize: MainAxisSize.max,
verticalDirection: verticalDirection,
children: children,
textBaseline: textBaseline,
textDirection: textDirection,
),
),
),
),
);
},
);
}
}
Solution 3 - Flutter
The answer is in the error itself. When the column is inside a view that is scrollable, the column is trying to shrink-wrap its content but since you used Expanded as a child of the column it is working opposite to the column trying to shrink-wrap its children. This is causing this error because these two directives are completely opposite to each other.
As mentioned in the error logs try the following:
Consider setting mainAxisSize to MainAxisSize.min (for column) and using FlexFit.loose fits for the flexible(use Flexible rather than Expanded).
Solution 4 - Flutter
I tried Vijaya Ragavan solution but did some adjustments to it & it still works.
To use Expanded with SingleChildScrollView, I used ConstrainedBox and set its height to the height of the screen (using MediaQuery). You'll just need to make sure the screen content you put inside ConstrainedBox is not bigger than the height of the screen.
Otherwise set the height of ConstrainedBox to height of the content you want to display on the screen.
SingleChildScrollView(
child: ConstrainedBox(
constraints: BoxConstraints(maxHeight: MediaQuery.of(context).size.height),
child: Column(
mainAxisAlignment: MainAxisAlignment.center,
crossAxisAlignment: CrossAxisAlignment.stretch,
children: <Widget>[
Expanded(
child: Text('Hello World!'),
),
],
),
)
)
Edit:
To subtract the height of the AppBar and/or the Status Bar, see below:
double screenHeightMinusAppBarMinusStatusBar = MediaQuery.of(context).size.height
- appBar.preferredSize.height
- MediaQuery.of(context).padding.top;
Solution 5 - Flutter
Simply wrap your SingleChildScrollView in a Center or an Align element.
Example :
Align(
alignment: Alignment.topCenter,
child: SingleChildScrollView(
child: Column(
children: <Widget>[
...
]
}
}
}
or
Center(
child: SingleChildScrollView(
child: Column(
children: <Widget>[
...
]
}
}
}
Solution 6 - Flutter
As already pointed out, because you are using a scrollable, you can't expand to the infinity (theoretically speaking), that's what's happening when you try to expand your ListView that is nested in a SingleChildScrollView.
You can try using a NestedScrollView, or, if it fits your demands and because you have commented out this line:
//height: MediaQuery.of(context).size.width*0.33,
You can just wrap your ListView in a ConstrainedBox (or even just a regular Container) with that height, for example, instead of the Expanded, like so:
Container(
height: MediaQuery.of(context).size.width*0.33,
child: ListView.builder(
itemCount: commentList.length,
...
)
)
Since you are already in a scrollable, you shouldn't have issues with smaller screens, because the whole tree is scrollable.
Solution 7 - Flutter
The trick is to only apply the ScrollView when you need to, and otherwise to let the content expand.
Something like this works well:
class ConstrainedFlexView extends StatelessWidget {
final Widget child;
final double minSize;
final Axis axis;
const ConstrainedFlexView(this.minSize, {Key key, this.child, this.axis}) : super(key: key);
bool get isHz => axis == Axis.horizontal;
@override
Widget build(BuildContext context) {
return LayoutBuilder(
builder: (_, constraints) {
double viewSize = isHz ? constraints.maxWidth : constraints.maxHeight;
if (viewSize > minSize) return child;
return SingleChildScrollView(
scrollDirection: axis ?? Axis.vertical,
child: ConstrainedBox(
constraints: BoxConstraints(
maxHeight: isHz ? double.infinity : minSize,
maxWidth: isHz ? minSize : double.infinity),
child: child,
),
);
},
);
}
}
Usage:
ConstrainedFlexView(600, child: FlexContent())
This will flex to fill all vertical space, but once the widget is <600px it will switch to a constrained box + scroll view, allowing the content not to be squished too much.
Solution 8 - Flutter
If what you want is:
- Being able to use expanded inside the SingleChildScrollView to fill the remaining screen.
- Not being bothered by the keyboard either hidding the TextFormField you are writing into either resizing the content of the SingleChildScrollView.
I had the same problem. Here is a maybe hazardous but in my case working solution I used:
import 'package:flutter/material.dart';
class FiniteSizeSingleChildScrollViewNotBotheredByKeyboard
extends StatefulWidget {
final Widget child;
const FiniteSizeSingleChildScrollViewNotBotheredByKeyboard(
{Key? key, required this.child})
: super(key: key);
@override
State<FiniteSizeSingleChildScrollViewNotBotheredByKeyboard> createState() =>
_FiniteSizeSingleChildScrollViewNotBotheredByKeyboardState();
}
class _FiniteSizeSingleChildScrollViewNotBotheredByKeyboardState
extends State<FiniteSizeSingleChildScrollViewNotBotheredByKeyboard> {
double width = 0, height = 0;
@override
Widget build(BuildContext context) {
return LayoutBuilder(builder: (context, constraints) {
if (width != constraints.maxWidth) {
width = constraints.maxWidth;
height = constraints.maxHeight;
}
return SingleChildScrollView(
child: SizedBox(
width: width,
height: height,
child: widget.child,
),
);
});
}
}
The idea is to get the available size just before the SingleChildScrollView, and then to inject this size into a SizedBox which is inside the SingleChildScrollView. Also, to avoid the keyboard changing this size, there is a if condition which prevents changing the height if the width has not changed.
The only issue I uncontered yet with this custom widget, is that if a TextFormField controller inside this widget (lets call it widget A) call setState on a widget B containing this widget A which itself is a child of the keyed Form associated with the TextFormField, The contoller will trigger a rebuild at the same time as the keyboard will trigger a rebuild of the widget A, which generate an exception. To avoid this put the keyed Form inside the widget A (and not above).
Solution 9 - Flutter
Most of the answers are not taken into account wich you have a textfield widget, so when the keyboard open you will get a problem with the size of your content (it will be heigher than the screen), so you should to wrap one of the widgets inside the (expanded) at least with (flexible).
Scaffold(
resizeToAvoidBottomInset: true,
body:CustomScrollView(
slivers: [
SliverFillRemaining(
hasScrollBody: false,
child: Column(
children: <Widget>[
const TextField(),
Expanded(
child: Column(
children: [
Flexible(child: someWidget()),
]
)
),
],
),
),
],
)
)
Solution 10 - Flutter
You can simply wrap the column in a sized box and give it a width and height as shown:
SingleChildScrollView(
child: SizedBox(
width: MediaQuery.of(context).size.width,
height: MediaQuery.of(context).size.height * 0.9,
child: Column(
mainAxisSize: MainAxisSize.min,
children: [
Container() //widget here
const Expanded(
child: SizedBox(),
),
Container() //widget here
],
),