Related
I'm trying to create a listview widget with a floating action button on my Flutter app, but it's not working because Android Studio keeps on telling me that:
"the named parameter children isn't defined"
I basically can't put children in a body: Center widget, but I don't know why
I'm basically a beginner to Flutter and I'm still a bit confused about the basic syntax, and which widgets can hold which widgets, so any help is greatly appreciated! Thank you!
Here's my overall code that won't run due to the first error (in quotation marks above):
import 'package:flutter/material.dart';
void main() => runApp(MaterialApp(
home: Home(),
));
class Home extends StatelessWidget {
#override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
backgroundColor: Colors.green[300],
title: Text(
'Welcome',
style: TextStyle(
fontSize: 25.0,
fontFamily: 'Raleway',
letterSpacing: 1.0,
),
),
centerTitle: true,
),
body: Center(
children: <Widget> [
ListView(
children: <Widget>[
Container(
height: 50,
color: Colors.green[100],
child: Text(
'Body Text',
style: TextStyle(
fontFamily: 'Raleway',
fontSize: 45.0,
letterSpacing: 1.0,
color: Colors.green[300],
),
),
),
Container(
height: 50,
color: Colors.green[100],
child: Text(
'Text'
),
),
],
),
FloatingActionButton(
onPressed: () {},
child: Text(
'+',
style: TextStyle(
fontFamily: 'Raleway',
fontSize: 35.0,
),
),
backgroundColor: Colors.green[300],
),
]
),
);
}
}
child parameter of Center Widget has a data type of Widget and so it can't take <Widget>[] as an input. It is similar to that an int won't accept String value. They are two different data types.
It seems that you want to have a list of data that is in center of the screen: For that you can use following code.
1.
Center(
child: Column(
mainAxisAlignment: MainAxisAlignment.center, // (optional) will center horizontally.
children: <Widget>[
.....
]
)
2.
Center(
child: ListView(
shrinkWrap:true;
children: <Widget>[
.....
]
)
)
It's simple. Because Center is a widget that does not take more than on widget as input.
It can only align one widget provided as a child.
For mulitple children you have to use some widget that takes a list of widgets as input.
Like:
Column
Row
ListView
Wrap
etc.
Center accepts only one widget check laytout page at https://flutter.dev/docs/development/ui/layout
Column(mainAxisAlignment: MainAxisAlignment.center,
mainAxisSize: MainAxisSize.max,
children: <Widget> [
ListView(
children: <Widget>[
Container(
height: 50,
color: Colors.green[100],
child: Text(
'Body Text',
style: TextStyle(
fontFamily: 'Raleway',
fontSize: 45.0,
letterSpacing: 1.0,
color: Colors.green[300],
),
),
),
Container(
height: 50,
color: Colors.green[100],
child: Text(
'Text'
),
),
],
),
FloatingActionButton(
onPressed: () {},
child: Text(
'+',
style: TextStyle(
fontFamily: 'Raleway',
fontSize: 35.0,
),
),
backgroundColor: Colors.green[300],
),
]
),
);
Center is a widget that centres its child within itself.
So you can have only 1 child inside Center Widget.
You can take structure like,
Center(
child: Column(
children: <Widget>[
All Children you have
]
)
There are two types of widgets, one of which accepts a widget as a child and the other one accepts [Widget] as children.
Accepts a Widget as Child: Container widget, Center widget, Padding widget, , etc.
Accepts [Widget] as Children: Row widget, Column widget, Stack widget, Wrap widget, ListView widget, etc.
Center class :
A widget that centers its child within itself.
All layout widgets have either of the following:
A child property if they take a single child—
for example, Center or Container
A children property if they take a list of widgets—
for example, Row, Column, ListView, or Stack.
Add the Text widget to the Center widget:
const Center(
child: Text('Hello World'),
),
I am trying to expand widget inside of Column widget but not able to make it expended.
When giving constant height to parent widget, the layout will be rendered as expected. But as I remove the constant height layout is not as expected as I want to make Listview with it and I should not give a constant height to the widget which will be used as listview item.
Below is my layout code.
import 'package:flutter/material.dart';
void main() {
runApp(MaterialApp(
title: 'layout test',
home: Layout_test_class(),
));
}
class Layout_test_class extends StatelessWidget {
Widget cell() {
return Container(
color: Colors.yellow,
// height: 200, after un commenting this will work. but i want to make it without this
child: Row(
crossAxisAlignment: CrossAxisAlignment.end,
mainAxisSize: MainAxisSize.max,
children: <Widget>[
Expanded(
child: Column(
mainAxisSize: MainAxisSize.max,
crossAxisAlignment: CrossAxisAlignment.stretch,
children: <Widget>[
Expanded(
child: Container(
color: Colors.green,
child: Text('apple z'),
),
),
Container(
color: Colors.red,
child:Text('apple 2'),
)
],
),
),
Column(
children: <Widget>[
Container(
color: Colors.black,
width: 200,
height: 200,
),
],
),
],
),
);
}
#override
Widget build(BuildContext context) {
// TODO: implement build
return Scaffold(
appBar: AppBar(
title: Text('title'),
),
body: Center(
child: ListView(
children: <Widget>[
cell(),
],
)
),
);
}
}
Below is my expected output screenshot.
Try to wrap your Container with IntrinsicHeight
return IntrinsicHeight(
Container(
color: Colors.yellow
child: ...
)
)
Your ListView needs to be inside Flexible. Flexible inside Column will set maximum height available to ListView. ListView needs a finite height from parent, Flexible will provide that based on max. space available.
Column(
children: <Widget>[
Flexible(
child: ListView.builder(...)
),
Container(
color: Colors.red,
child:Text('apple 2'),
),
],
)
A nice way of doing this, it's to play with the MediaQuery, heigth and width.
Let me explain, if you want the widget to have the maximum heigth of a decide screen, you can set it like this:
Container(
height: MediaQuery.of(context).size.height // Full screen size
)
You can manipulate it by dividing by 2, 3, 400, the value you want.
The same things works for the width
Container(
width: MediaQuery.of(context).size.width // Can divide by any value you want here
)
Actually quite the opposite, if you're planning to use this as an item in a listViewyou can't let infinite size on the same axis your listView is scrolling.
Let me explain:
Currently you're not defining any height on your cell() widget, which is fine if you're using it alone. like this :
import 'package:flutter/material.dart';
void main() {
runApp(MaterialApp(
title: 'layout test',
home: Layout_test_class(),
));
}
class Layout_test_class extends StatelessWidget {
Widget cell() {
return Container(
color: Colors.yellow,
//height: 250, after un commenting this will work. but i want to make it without this
child: Row(
crossAxisAlignment: CrossAxisAlignment.end,
mainAxisSize: MainAxisSize.max,
children: <Widget>[
Expanded(
child: Column(
mainAxisSize: MainAxisSize.max,
crossAxisAlignment: CrossAxisAlignment.stretch,
children: <Widget>[
Expanded(
child: Container(
color: Colors.green,
child: Text('apple z'),
),
),
Container(
color: Colors.red,
child: Text('apple 2'),
)
],
),
),
Column(
children: <Widget>[
Container(
color: Colors.black,
width: 200,
height: 200,
),
],
),
],
),
);
}
#override
Widget build(BuildContext context) {
// TODO: implement build
return Scaffold(
appBar: AppBar(
title: Text('title'),
),
body: cell(),
);
}
}
But using it with a listView you have to define a height. A listView scrolls as long as it have some content to scroll. Right now it just like you're giving it infinite content so it would scroll indefinitely. Instead Flutter is not constructing it.
It's actually quite ok to define a global size for your container (as an item). You can even define a specific size for each using a parameter like this :
import 'package:flutter/material.dart';
void main() {
runApp(MaterialApp(
title: 'layout test',
home: Layout_test_class(),
));
}
class Layout_test_class extends StatelessWidget {
Widget cell(double height) {
return Container(
color: Colors.yellow,
height: height, //after un commenting this will work. but i want to make it without this
child: Row(
crossAxisAlignment: CrossAxisAlignment.end,
mainAxisSize: MainAxisSize.max,
children: <Widget>[
Expanded(
child: Column(
mainAxisSize: MainAxisSize.max,
crossAxisAlignment: CrossAxisAlignment.stretch,
children: <Widget>[
Expanded(
child: Container(
color: Colors.green,
child: Text('apple z'),
),
),
Container(
color: Colors.red,
child: Text('apple 2'),
)
],
),
),
Column(
children: <Widget>[
Container(
color: Colors.black,
width: 200,
height: 200,
),
],
),
],
),
);
}
#override
Widget build(BuildContext context) {
// TODO: implement build
return Scaffold(
appBar: AppBar(
title: Text('title'),
),
body: ListView(
children: <Widget>[
cell(250.0),
cell(230.0),
cell(300.0),
],
)
);
}
}
I want to center a Text vertically in the bottom: Sektion of my AppBar.
Some things I allready tried are:
1. wrap the Text in a Center(...) Widget
2. wrap the Text in a Column(...) and use crossAxisAlignment: CrossAxisAlignment.center
The bottom: Sektion is a PreferredSizeWidget and does not provide anything to format a Widget.
appBar: new AppBar(
actions: <Widget>[
IconButton(
icon: Icon(Icons.settings),
onPressed: () {
print("Settings Icon");
},
),
],
bottom: PreferredSize(
preferredSize: Size(130.0, 130.0),
child: Column(
crossAxisAlignment: CrossAxisAlignment.center,
children: <Widget>[
new Text(
'N/A',
),
],
),
),
),
I have have found this issue here: https://github.com/flutter/flutter/issues/16262 where the Text was centered but the reproduce code did not worked out for me.
The Text should me somewhere like the red line is (see Image)
Thank you!
PreferredSizeWidget does not impose a size constraint on its child, so you must wrap the Column in a widget with defined height in order to add alignment.
Also, mainAxisAlignment should be used, since this is the vertical alignment in a Column.
bottom: PreferredSize(
preferredSize: Size(130.0, 130.0),
child: Container(
height: 130,
child: Column(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
new Text(
'N/A',
),
],
),
),
)
I am trying to make a simple chat app, so I created a scaffold and my body, will be the messages and my bottomNavigationBar would be my typing field and sending icon.
I added a text field but when typing the navigation bar is hidden by the keyboard.
this is the code of my BottomNavigationBar :
bottomNavigationBar: new Container(
height: ScreenSize.height/12,
/*color: Colors.red,*/
child: new Row(
mainAxisAlignment: MainAxisAlignment.spaceEvenly,
children: <Widget>[
new Column(
mainAxisAlignment: MainAxisAlignment.spaceAround,
children: <Widget>[
new Container(
child: new Icon(Icons.send),
width:ScreenSize.width/6,
),
],
),
new Column(
mainAxisAlignment: MainAxisAlignment.spaceAround,
children: <Widget>[
Material(
child: new Container(
child: new TextField(
autofocus: false,
decoration: InputDecoration(
contentPadding: EdgeInsets.all(9.0),
border: InputBorder.none,
hintText: 'Please enter a search term',
),
),
width:ScreenSize.width*4/6,
),
elevation: 4.0,
/*borderRadius: new BorderRadius.all(new Radius.circular(45.0)),*/
clipBehavior: Clip.antiAlias,
type: MaterialType.card,
)
],
),
new Column(
mainAxisAlignment: MainAxisAlignment.spaceAround,
children: <Widget>[
new Container(
child: Text('HELLO C1'),
color: Colors.green,
width:ScreenSize.width/6,
),
],
)
],
),
),
here is how it looks when focused :
if you use a Stack on your Scaffold's body, instead of bottomNavigationBar, your nav will push up above the keyboard. even if you fix to the bottom with a Positioned:
Positioned(
bottom: 0.0,
left: 0.0,
right: 0.0,
child: MyNav(),
),
simply wrap your bottom navigation bar with Padding and set it to MediaQuery.of(context).viewInsets,
bottomNavigationBar: Padding(
padding: MediaQuery.of(context).viewInsets,
child: ChatInputField(),
),
Literally just worked through the same issue. Given the code i was refactoring, this worked like a charm. Peep the github link, review his change and apply. Couldn't be much more straight forward: https://github.com/GitJournal/GitJournal/commit/f946fe487a18b2cb8cb1d488026af5c64a8f2f78..
Content of the link above in case the link goes down:
(-)BottomAppBar buildEditorBottonBar(
(+)Widget buildEditorBottonBar(
BuildContext context,
Editor editor,
EditorState editorState,
BottomAppBar buildEditorBottonBar(
folderName = "Root Folder";
}
*REPLACE* return BottomAppBar(
elevation: 0.0,
color: Theme.of(context).scaffoldBackgroundColor,
child: Row(
children: <Widget>[
FlatButton.icon(
icon: Icon(Icons.folder),
label: Text(folderName),
onPressed: () {
var note = editorState.getNote();
editor.moveNoteToFolderSelected(note);
},
)
],
mainAxisAlignment: MainAxisAlignment.center,
*WITH THE WRAPPER* return StickyBottomAppBar(
child: BottomAppBar(
elevation: 0.0,
color: Theme.of(context).scaffoldBackgroundColor,
child: Row(
children: <Widget>[
FlatButton.icon(
icon: Icon(Icons.folder),
label: Text(folderName),
onPressed: () {
var note = editorState.getNote();
editor.moveNoteToFolderSelected(note);
},
)
],
mainAxisAlignment: MainAxisAlignment.center,
),
),
);
}
class StickyBottomAppBar extends StatelessWidget {
final BottomAppBar child;
StickyBottomAppBar({#required this.child});
#override
Widget build(BuildContext context) {
return Transform.translate(
offset: Offset(0.0, -1 * MediaQuery.of(context).viewInsets.bottom),
child: child,
);
}
}
I achieved this by a mix of two things I found separated in the web:
1 - Inside the Scaffold, I put other with only a bottomNavigationBar with a empty Container. For some reason, this trick push all my real bottomNavigationBar up to the top of the keyboard.
Scaffold(
bottomNavigationBar: Container(
height: 0,
),
body: Scaffold(
body: MyWidget(
But, I did not want all the content up, so I got that Package:
2 - I added flutter_keyboard_visibility: ^5.1.0 from
https://pub.dev/packages/flutter_keyboard_visibility
With this Package, you can do anything you want in response to keyboard visibility - is up to you. In my case, I made all content of my real bottomNavigationBar disappear except the textfield, which stay on the top of the keyboard:
[TextFormField] // dont go away,
//The others:
KeyboardVisibilityBuilder(builder: (context, visible) {
return Column(
children: [
visible
? SizedBox(
height: 0,
)
: OtherWidgets(
If you need some kind of button; you can do:
Scaffold(
bottomNavigationBar: bottomNavigationBar,
floatingActionButton: ExampleButton(
text: 'Hello',
),
body: body,
),
You can apply further customizations on the Floating Action Button using parameters in the Scaffold.
There is a simple way to do this if you want to really need to use the bottom navigation bar of the scaffold to put your widgets in rather than put it on a stack. Just wrap your scaffold with another scaffold and it should solve the problem.
return Scaffold(
body: Scaffold(
bottomNavigationBar: yourBottomNavigationBarWidget(),
body: yourBody(),
This works best especially when the height of your widget changes dynamically (because the text user types may introduce multiple lines) and you want the body to resize accordingly. A body in the stack, as suggested by many, will require a bottom padding to be visible over the text field and need to change dynamically as user types which is difficult to handle when you have multiple widgets sitting in and around the text field.
I'm trying to have a Widget align to the bottom of my NavDrawer while still keeping a DrawerHeader and a list at the top of the Drawer. Here's what I'm trying:
drawer: new Drawer(
child: new Column(
mainAxisSize: MainAxisSize.max,
children: <Widget>[
new Text('Top'),
new Align(
alignment: FractionalOffset.bottomCenter,
child: new Text('Bottom'),
),
],
),
),
The bottom text should be aligned to the bottom of the drawer, but It isn't!
You need to wrap your Align widget in Expanded.
drawer: Drawer(
child: Column(
mainAxisSize: MainAxisSize.max,
children: <Widget>[
Text('Top'),
Expanded(
child: Align(
alignment: Alignment.bottomCenter,
child: Text('Bottom'),
),
),
],
),
),
Edit:
Years on and there's a much easier solution:
return Drawer(
child: Column(
children: [
ListView(), // <-- Whatever actual content you want goes here
Spacer(), // <-- This will fill up any free-space
// Everything from here down is bottom aligned in the drawer
Divider(),
ListTile(
title: Text('Settings'),
leading: Icon(Icons.settings),
),
ListTile(
title: Text('Help and Feedback'),
leading: Icon(Icons.help),
),
]
);
A little late to the party, but here's my solution to this problem:
#override
Widget build(BuildContext context) {
return Drawer(
// column holds all the widgets in the drawer
child: Column(
children: <Widget>[
Expanded(
// ListView contains a group of widgets that scroll inside the drawer
child: ListView(
children: <Widget>[
UserAccountsDrawerHeader(),
Text('In list view'),
Text('In list view too'),
],
),
),
// This container holds the align
Container(
// This align moves the children to the bottom
child: Align(
alignment: FractionalOffset.bottomCenter,
// This container holds all the children that will be aligned
// on the bottom and should not scroll with the above ListView
child: Container(
child: Column(
children: <Widget>[
Divider(),
ListTile(
leading: Icon(Icons.settings),
title: Text('Settings')),
ListTile(
leading: Icon(Icons.help),
title: Text('Help and Feedback'))
],
)
)
)
)
],
),
);
}
This produces the below output where the UserAccountDrawerHeader and the text items can be scrolled around inside the drawer but the Divider and the two ListTiles stay static on the bottom of the drawer.
look whats the problem with your code you have added a Column as a Child to the Drawer so whatever you add in it are vertically placed and The height of Column is by default shrunk to its children's height and it gets larger as the child gets, so there's no point in adding an Align inside a Column
The Simpler Solution Would be to use an Expanded Widget that takes the remaining Space Look I have used a Column and added A widget above and below the Expanded Widget.
Drawer(
elevation: 1.5,
child: Column(children: <Widget>[
DrawerHeader(
decoration: BoxDecoration(
color: Colors.redAccent,
)),
Expanded(
child: ListView(
padding: EdgeInsets.zero,
children: <Widget>[
ListTile(
title: Text('My Cart'),
leading: Icon(Icons.shopping_cart),
onTap: () {},
),
ListTile(
title: Text('My Orders'),
leading: Icon(Icons.add_shopping_cart),
onTap: () {},
),
ListTile(
title: Text('Logout'),
leading: Icon(Icons.exit_to_app),
onTap: () {})
],
)),
Container(
color: Colors.black,
width: double.infinity,
height: 0.1,
),
Container(
padding: EdgeInsets.all(10),
height: 100,
child: Text("V1.0.0",style: TextStyle(fontWeight: FontWeight.bold),)),
])),
A simple approach would be to use Spacer() like:
Scaffold(
drawer: Drawer(
child: Column(
children: <Widget>[
Text('Top'),
Spacer(), // use this
Text('Bottom'),
],
),
)
)
here is my solution of a vertical Row with icons in the end of the drawer.
#override
Widget build(BuildContext context) {
return Drawer(
child: Column(
children: <Widget>[
Expanded(
child: ListView(
children: <Widget>[
DrawerHeader(
padding: const EdgeInsets.all(7),
decoration: BoxDecoration(
color: AppColors.menuHeaderColor,
),
child: buildHeader(),
),
AccountDrawerRow(),
ListTile(
leading: Icon(Icons.directions_car),
title: Text(translations.button.vehicles),
),
ListTile(
leading: Icon(Icons.calendar_today),
title: Text(translations.button.appointments,),
),
],
),
),
Container(
child: Align(
alignment: FractionalOffset.bottomCenter,
child: Container(
padding: EdgeInsets.all(15.0),
child: Row(
mainAxisAlignment: MainAxisAlignment.spaceAround,
children: <Widget>[
InkWell(
onTap: () => Navigator.of(context).push(MaterialPageRoute(
builder: (context) => SettingsPage())),
child: Icon(Icons.settings)),
Icon(Icons.help),
Icon(Icons.info),
],
),
),
),
),
],
),
);
}
I'd put it in a row and align all the stuff to bottom using crossAxisAlignment: CrossAxisAlignment.baseline
Row(
mainAxisSize: MainAxisSize.max,
crossAxisAlignment: CrossAxisAlignment.baseline,
children: <Widget>[
Text(
'12.00',
style: Theme.of(context).textTheme.headline2,
textAlign: TextAlign.start,
),
Text(
'USD',
style: Theme.of(context).textTheme.bodyText2,
textAlign: TextAlign.start,
),
]),
Using Expanded widget to align widget to bottom of column parent widget
Column(
children: [
..other children
Expanded(
child: Align(
alignment: Alignment.bottomCenter,
child: Text(
'Button',
style: TextStyle(
decoration: TextDecoration.underline,
fontSize: 18,
color: Colors.black),
),
),
),
],
),