I tried using this kind of approach to have all of my UI (here only a Text) in the application below the status bar, but without AppBar:
import 'package:flutter/material.dart';
void main() => runApp(MaterialApp(
title: "example",
home: Scaffold(
body: Text("text widget"),
),
));
This question was already asked once similar to my text, but the answer to it (which is also accepted) only takes margin into account. This, to me, does not seem like a satisfying solution, especially because you need to access MediaQuery.of(context).padding, where I could not even figure out how to use context in my simple example.
My code gives me the following result:
But I want to see this:
Now to make the differenciation between my question and the other question clear: I am not searching for a margin, I am searching for a legitimate idiomatic way of doing this. What I mean with this might look like this:
ScaffoldWithoutAppBar(body: ...
Obviously this does not exist, but I do not want a margin fix.
Wrap your page content (Text or Scaffold) inside a SafeArea widget
A widget that insets its child by sufficient padding to avoid intrusions by the operating system.
return new SafeArea(child: new Text('text widget'));
first solution: My favorite solution
appBar: PreferredSize(
preferredSize: Size.fromHeight(MediaQuery.of(context).padding.top),
child: SizedBox(
height: MediaQuery.of(context).padding.top,
),
),
solution (2):
body: SafeArea(
top: true,
left: false,
right: false,
bottom: false,
child:Container(),
)
solution (3):
body: ListView(
children:[],
)
You can wrap the Scaffold into SafeArea, as below:
import 'package:flutter/material.dart';
void main() => runApp(MyApp(
textInput: Text("Text Widget"),
));
class MyApp extends StatefulWidget {
final Widget textInput;
MyApp({this.textInput});
#override
State<StatefulWidget> createState() => MyAppState();
}
class MyAppState extends State<MyApp> {
bool checkBoxValue = false;
#override
Widget build(BuildContext ctxt) {
return new MaterialApp(
home: SafeArea(
child: Scaffold(
body: new Center(
child: new Column(
children: <Widget>[
widget.textInput,
Checkbox(
value: checkBoxValue,
onChanged: (bool newValue){
setState(() {
checkBoxValue = newValue;
});
}
)
],
))),
),
);
}
}
About the opposite, in case you do not need to keep repeating the AppBar in your multiple screens, you can create separate widget:
import 'package:flutter/material.dart';
import 'state.dart';
AppBar commonAppBar(String title, void action()) {
return new AppBar(
title: new Text(title),
actions: [
new IconButton(icon: new Icon(Icons.flip), onPressed: action),
new IconButton(icon: new Icon(Icons.exit_to_app), onPressed: () {
new StateSubject().switchToLogin();
}),
],
);
}
Related
I am new to the flutter application development and got stuck in a problem.My application contains near about 5-6 screens and all the screens contains the scaffold widget like this.
#override
Widget build(BuildContext context) {
return Scaffold(
backgroundColor: const Color(0xFF332F43)
);
}
Now on all the screens i have the same concept and design like this and all the screens will share same backGround color.Now i have a button in all screens i.e. Change Theme button and on the button click of that Change Theme button i want to change all the screens Scaffold widget to be changed.Now how can i achieve this ? Please help me in my problem.
Flutter has predefined way to change background color of scaffold across app.
Just change it in MaterialApp Widget inside of your main.dart (main file).
MaterialApp(
title: 'Flutter',
theme: ThemeData(
scaffoldBackgroundColor: const Color(0xFF332F43),
),
);
Color color = Colors.blue; // make it at root level
void main() {
runApp(MaterialApp(home: Page1()));
}
In your page1 class, import above file.
class Page1 extends StatefulWidget {
#override
_Page1State createState() => _Page1State();
}
class _Page1State extends State<Page1> {
#override
Widget build(BuildContext context) {
return Scaffold(
backgroundColor: color,
appBar: AppBar(title: Text("Page 1")),
body: Center(
child: Column(
children: <Widget>[
RaisedButton(
onPressed: () => Navigator.push(context, MaterialPageRoute(builder: (c) => Page2())),
child: Text("Go to Page 2"),
),
RaisedButton(
child: Text("Change color"),
onPressed: () => setState(() => color = Colors.red),
),
],
),
),
);
}
}
In your page2 class, import first file.
class Page2 extends StatefulWidget {
#override
_Page2State createState() => _Page2State();
}
class _Page2State extends State<Page2> {
#override
Widget build(BuildContext context) {
return Scaffold(
backgroundColor: color,
appBar: AppBar(title: Text("Page 2")),
body: Center(
child: Column(
children: <Widget>[
RaisedButton(
onPressed: () => Navigator.pop(context),
child: Text("Back"),
),
RaisedButton(
child: Text("Change color"),
onPressed: () => setState(() => color = Colors.green),
),
],
),
),
);
}
}
I'm trying to display a SnackBar after performing an action from the AppBar.
The AppBar cannot be built from a builder so it can't access is Scaffold ancestor.
I know we can use a GlobalKey object to access the context whenever we want, but I would like to know if there is a solution without using the GlobalKey.
I found some github issues and pull-request, but I can't find a solution from them
=> https://github.com/flutter/flutter/issues/4581 and https://github.com/flutter/flutter/pull/9380
Some more context:
I have an Appbar with a PopupMenuButton, which have one item. When the user click on this item I display a dialog which the showDialog method and if the user clicks on "ok" I want to display a SnackBar
You can use the Builder widget
Example:
Scaffold(
appBar: AppBar(
actions: <Widget>[
Builder(
builder: (BuildContext context) {
return IconButton(
icon: const Icon(Icons.message),
onPressed: () {
final snackBar = SnackBar(content: Text('Yay! A SnackBar!'));
Scaffold.of(context).showSnackBar(snackBar);
},
);
},
),
],
)
);
The Scaffold.appBar parameter requires a PreferredSizeWidget, so you can have a Builder there like this:
appBar: PreferredSize(
preferredSize: Size.fromHeight(56),
child: Builder(
builder: (context) => AppBar(...),
),
),
An option is to use two contexts in the dialog and use the context passed to the dialog to search for the Scaffold.
When you show a dialog, you are displaying a completely different page/route which is outside the scope of the calling page. So no scaffold is available.
Below you have a working example where you use the scope of the first page.
The problem, though, is that the SnackBar is not removed.
If instead you use a GlobalKey to get the Scaffold the problem is the same.
I would consider not using a Snackbar in this case, because it is associated to the page below. It is even greyed out by the dialog shadow.
import 'package:flutter/material.dart';
void main() => runApp(new MyApp());
class MyApp extends StatelessWidget {
#override
Widget build(BuildContext context) {
return new MaterialApp(
home: new MyHomePage(),
);
}
}
class MyHomePage extends StatelessWidget {
_showDialog(BuildContext context1) {
return showDialog(
context: context1,
builder: (BuildContext context) {
return AlertDialog(
content: Text("Dialog"),
actions: <Widget>[
new FlatButton(
child: new Text("OK"),
onPressed: () => Scaffold.of(context1).showSnackBar(SnackBar(
content: Text("Pressed"),
)),
),
],
);
});
}
#override
Widget build(BuildContext context) {
return new Scaffold(
appBar: new AppBar(
title: new Text("Test"),
actions: <Widget>[
PopupMenuButton(
itemBuilder: (BuildContext context) {
return <PopupMenuEntry>[
PopupMenuItem(
child: ListTile(
title: Text('Show dialog'),
onTap: () => _showDialog(context),
),
),
];
},
)
],
),
);
}
}
I have two easy basics example one is Works and second need some of explaining.
So, When I Clik Button in Example one it Works and setStaet rendering the page.
Second Example I using a body function that has setState of Button. When I click button nothing happen even with using setState notes if
the variable inside the parenthesis it does not render.
When I make Variable instance in class it works fine but I need to rendering Only One Button how?
Full code Example One
import 'package:flutter/material.dart';
main() => runApp(MaterialApp(
home: Home(),
));
class Home extends StatefulWidget {
#override
_HomeState createState() => _HomeState();
}
class _HomeState extends State<Home> {
bool istrue = false;
#override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(title: Text('Works fine'),),
body: Center(child: body()),
);
}
Widget body() {
return Column(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
RaisedButton(
onPressed: () {
setState(() {
istrue = !istrue;
});
},
child: Text('Click me'),
),
Padding(
padding: const EdgeInsets.all(8.0),
child: Text(istrue ? 'Boo!' : ''),
),
],
);
}
}
Full code Example two
import 'package:flutter/material.dart';
main() => runApp(MaterialApp(
home: Home(),
));
class Home extends StatefulWidget {
#override
_HomeState createState() => _HomeState();
}
class _HomeState extends State<Home> {
bool istrue = false;
#override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(title: Text('Works fine'),),
body: Center(child: Column(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
body(),body(),
],
)),
);
}
Widget body() {
return Column(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
RaisedButton(
onPressed: () {
setState(() {
istrue = !istrue;
});
},
child: Text('Click me'),
),
Padding(
padding: const EdgeInsets.all(8.0),
child: Text(istrue ? 'Boo!' : ''),
),
],
);
}
}
Thanks as sky.
I am having a bit of trouble understanding your question, but I also understand that English is not your first language. You seem to be asking, "How can I render only one button for example #2?". Please let me know if this is not your question so that I, and others, can help you.
This will only render one button,
import 'package:flutter/material.dart';
main() => runApp(MaterialApp(
home: Home(),
));
class Home extends StatefulWidget {
#override
_HomeState createState() => _HomeState();
}
class _HomeState extends State<Home> {
bool istrue = false;
#override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(title: Text('Works fine'),),
body: Center(child: Column(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
RaisedButton(
onPressed: () {
setState(() {
istrue = !istrue;
});
},
child: Text('Click me'),
),
Padding(
padding: const EdgeInsets.all(8.0),
child: Text(istrue ? 'Boo!' : ''),
),
Padding(
padding: const EdgeInsets.all(8.0),
child: Text(istrue ? 'Boo!' : ''),
),
],
)),
);
}
}
You are calling a Column widget within another Column widget in the Scaffold widget in your second example. Why would you do that? There are many ways to structure that layout in the flutter API.
You can't have a new Column(new Column(...)); Its redundant.
Edit:
I pulled this from the flutter website at Column class:
The Column widget does not scroll (and in general it is considered an error to have more children in a Column than will fit in the available room). If you have a line of widgets and want them to be able to scroll if there is insufficient room, consider using a ListView.
I have this:
final GlobalKey<ScaffoldState> _scaffoldkey = new GlobalKey<ScaffoldState>();
#override
Widget build(BuildContext context) {
return DefaultTabController(
length: 2,
child: Scaffold(
key: _scaffoldkey,
drawer: Menu(),
appBar: AppBar(
title: Container(
child: Text('Dashboard'),
),
bottom: TabBar(
tabs: <Widget>[
...
],
),
),
body: TabBarView(
children: <Widget>[
...
],
),
),
);
}
}
Now, the drawer: Menu() is imported from another menu.dart file, which looks like this:
class Menu extends StatelessWidget {
final GlobalKey<ScaffoldState> drawerKey = new GlobalKey<ScaffoldState>();
#override
Widget build(BuildContext context) {
return new Drawer(
key: drawerKey,
child: new ListView(
children: <Widget>[
new ListTile(
dense: true,
title: new Text('My Text'),
onTap: () {
// On tap this, I want to show a snackbar.
scaffoldKey.currentState.showSnackBar(showSnack('Error. Could not log out'));
},
),
],
),
);
}
}
With the above approach, I get
NoSuchMethodError: The method 'showSnackBar' was called on null.
An easy solution is to tuck the entire menu.dart contents in the drawer: ... directly.
Another way I'm looking at is being able to reference the parent scaffold in order to display the snackbar.
How can one achieve that?
Why can't one even just call the snackbar from anywhere in Flutter and compulsorily it has to be done via the Scaffold? Just why?
You should try to avoid using GlobalKey as much as possible; you're almost always better off using Scaffold.of to get the ScaffoldState. Since your menu is below the scaffold in the widget tree, Scaffold.of(context) will do what you want.
The reason what you're attempting to do doesn't work is that you are creating two seperate GlobalKeys - each of which is its own object. Think of them as global pointers - since you're creating two different ones, they point to different things. And the state should really be failing analysis since you're passing the wrong type into your Drawer's key field...
If you absolutely have to use GlobalKeys for some reason, you would be better off passing the instance created in your outer widget into your Menu class as a member i.e. this.scaffoldKey, but this isn't recommended.
Using Scaffold.of, this is what your code would look like in the onTap function:
onTap: () {
// On tap this, I want to show a snackbar.
Scaffold.of(context).showSnackBar(showSnack('Error. Could not log out'));
},
You can achieve this functionality by using builder widget you don't need to make separate GlobalKey or pass key as a parameter. Just wrap a widget to Builder widget
class CustomDrawer extends StatelessWidget {#override Widget build(BuildContext context) {
return new Drawer(
child: new ListView(
children: <Widget>[
new Builder(builder: (BuildContext innerContext) {
return ListTile(
dense: true,
title: new Text('My Text'),
onTap: () {
Navigator.of(context).pop();
Scaffold.of(innerContext).showSnackBar(SnackBar(
content: Text('Added added into cart'),
duration: Duration(seconds: 2),
action: SnackBarAction(label: 'UNDO', onPressed: () {}),
));
}
);
})
],
),
);}}
From your first question
In other to reference the parent scaffold in the menu widget you can pass the _scaffoldkey to the menu widget as parameter and use ScaffoldMessenger.of() to show snackbar as shown below
import 'package:flutter/material.dart';
void main() => runApp(MyApp());
class MyApp extends StatelessWidget {
// Root Widget
#override
Widget build(BuildContext context) {
return MaterialApp(
// App name
title: 'Flutter SnackBar',
// Theme
theme: ThemeData(
primarySwatch: Colors.blue,
),
home: Test(title: 'SnackBar'),
);
}
}
class Test extends StatefulWidget {
final String? title;
final GlobalKey<ScaffoldState> _scaffoldkey = new GlobalKey<ScaffoldState>();
Test({#required this.title});
#override
_TestState createState() => _TestState();
}
class _TestState extends State<Test> {
#override
Widget build(BuildContext context) {
return DefaultTabController(
length: 2,
child: Scaffold(
key: widget._scaffoldkey,
drawer: Menu(parentScaffoldkey:widget._scaffoldkey),
appBar: AppBar(
title: Container(
child: Text('Dashboard'),
),
bottom: TabBar(
tabs: <Widget>[
Tab(text:"Home"),
Tab(text:"About")
],
),
),
body: TabBarView(
children: <Widget>[
Text("Home"),
Text("About")
],
),
),
);
}
}
Menu part as shown
class Menu extends StatelessWidget {
final parentScaffoldkey;
Menu({this.parentScaffoldkey});
#override
Widget build(BuildContext context) {
return new Drawer(
child: new ListView(
children: <Widget>[
new ListTile(
dense: true,
title: new Text('My Text'),
onTap: () {
// On tap show a snackbar.
// ScaffoldMessenger will call the nearest Scaffold to show snackbar
ScaffoldMessenger.of(this.parentScaffoldkey.currentContext).showSnackBar(SnackBar(content:Text('Error. Could not log out')));
},
),
],
),
);
}
}
Also,you have to call snackbar via Scaffold because it provides the SnackBar API and manages it
Our app is built on top of Scaffold and to this point we have been able to accommodate most of our routing and navigation requirements using the provided calls within NavigatorState (pushNamed(), pushReplacementNamed(), etc.). What we don't want though, is to have any kind of 'push' animation when a user selects an item from our drawer (nav) menu. We want the destination screen from a nav menu click to effectively become the new initial route of the stack. For the moment we are using pushReplacementNamed() for this to ensure no back arrow in the app bar. But, the slide-in-from-the-right animation implies a stack is building.
What is our best option for changing that initial route without animation, and, can we do that while also concurrently animating the drawer closed? Or are we looking at a situation here where we need to move away from Navigator over to just using a single Scaffold and updating the 'body' directly when the user wants to change screens?
We note there is a replace() call on NavigatorState which we assume might be the right place to start looking, but it's unclear how to access our various routes originally set up in new MaterialApp(). Something like replaceNamed() might be in order ;-)
What you're doing sounds somewhat like a BottomNavigationBar, so you might want to consider one of those instead of a Drawer.
However, having a single Scaffold and updating the body when the user taps a drawer item is a totally reasonable approach. You might consider a FadeTransition to change from one body to another.
Or, if you like using Navigator but don't want the default slide animation, you can customize (or disable) the animation by extending MaterialPageRoute. Here's an example of that:
import 'package:flutter/material.dart';
void main() {
runApp(new MyApp());
}
class MyCustomRoute<T> extends MaterialPageRoute<T> {
MyCustomRoute({ WidgetBuilder builder, RouteSettings settings })
: super(builder: builder, settings: settings);
#override
Widget buildTransitions(BuildContext context,
Animation<double> animation,
Animation<double> secondaryAnimation,
Widget child) {
if (settings.isInitialRoute)
return child;
// Fades between routes. (If you don't want any animation,
// just return child.)
return new FadeTransition(opacity: animation, child: child);
}
}
class MyApp extends StatelessWidget {
#override
Widget build(BuildContext context) {
return new MaterialApp(
title: 'Navigation example',
onGenerateRoute: (RouteSettings settings) {
switch (settings.name) {
case '/': return new MyCustomRoute(
builder: (_) => new MyHomePage(),
settings: settings,
);
case '/somewhere': return new MyCustomRoute(
builder: (_) => new Somewhere(),
settings: settings,
);
}
assert(false);
}
);
}
}
class MyHomePage extends StatelessWidget {
#override
Widget build(BuildContext context) {
return new Scaffold(
appBar: new AppBar(
title: new Text('Navigation example'),
),
drawer: new Drawer(
child: new ListView(
children: <Widget> [
new DrawerHeader(
child: new Container(
child: const Text('This is a header'),
),
),
new ListTile(
leading: const Icon(Icons.navigate_next),
title: const Text('Navigate somewhere'),
onTap: () {
Navigator.pushNamed(context, '/somewhere');
},
),
],
),
),
body: new Center(
child: new Text(
'This is a home page.',
),
),
);
}
}
class Somewhere extends StatelessWidget {
Widget build(BuildContext context) {
return new Scaffold(
body: new Center(
child: new Text(
'Congrats, you did it.',
),
),
appBar: new AppBar(
title: new Text('Somewhere'),
),
drawer: new Drawer(
child: new ListView(
children: <Widget>[
new DrawerHeader(
child: new Container(
child: const Text('This is a header'),
),
),
],
),
),
);
}
}
Use PageRouteBuilder like:
Navigator.push(
context,
PageRouteBuilder(
pageBuilder: (_, __, ___) => Screen2(),
transitionDuration: Duration.zero,
),
);
And if you want transition, simply add following property to above PageRouteBuilder, and change seconds to say 1.
transitionsBuilder: (_, a, __, c) => FadeTransition(opacity: a, child: c),