AppBar Basics
A typical AppBar with a title, actions, and an overflow dropdown menu.
![Android screenshot](https://storage.googleapis.com/flutter-catalog/cb4a54db8fb3726bf4293b9cc5cb12ce16883803/basic_app_bar_small.png)
An app that displays one of a half dozen choices with an icon and a title. The two most common choices are available as action buttons and the remaining choices are included in the overflow dropdow menu.
Try this app out by creating a new project with flutter create
and replacing the contents of lib/main.dart
with the code that follows.
// Copyright 2017 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
import 'package:flutter/material.dart';
// This app is a stateful, it tracks the user's current choice.
class BasicAppBarSample extends StatefulWidget {
@override
_BasicAppBarSampleState createState() => new _BasicAppBarSampleState();
}
class _BasicAppBarSampleState extends State<BasicAppBarSample> {
Choice _selectedChoice = choices[0]; // The app's "state".
void _select(Choice choice) {
setState(() { // Causes the app to rebuild with the new _selectedChoice.
_selectedChoice = choice;
});
}
@override
Widget build(BuildContext context) {
return new MaterialApp(
home: new Scaffold(
appBar: new AppBar(
title: const Text('Basic AppBar'),
actions: <Widget>[
new IconButton( // action button
icon: new Icon(choices[0].icon),
onPressed: () { _select(choices[0]); },
),
new IconButton( // action button
icon: new Icon(choices[1].icon),
onPressed: () { _select(choices[1]); },
),
new PopupMenuButton<Choice>( // overflow menu
onSelected: _select,
itemBuilder: (BuildContext context) {
return choices.skip(2).map((Choice choice) {
return new PopupMenuItem<Choice>(
value: choice,
child: new Text(choice.title),
);
}).toList();
},
),
],
),
body: new Padding(
padding: const EdgeInsets.all(16.0),
child: new ChoiceCard(choice: _selectedChoice),
),
),
);
}
}
class Choice {
const Choice({ this.title, this.icon });
final String title;
final IconData icon;
}
const List<Choice> choices = const <Choice>[
const Choice(title: 'Car', icon: Icons.directions_car),
const Choice(title: 'Bicycle', icon: Icons.directions_bike),
const Choice(title: 'Boat', icon: Icons.directions_boat),
const Choice(title: 'Bus', icon: Icons.directions_bus),
const Choice(title: 'Train', icon: Icons.directions_railway),
const Choice(title: 'Walk', icon: Icons.directions_walk),
];
class ChoiceCard extends StatelessWidget {
const ChoiceCard({ Key key, this.choice }) : super(key: key);
final Choice choice;
@override
Widget build(BuildContext context) {
final TextStyle textStyle = Theme.of(context).textTheme.display1;
return new Card(
color: Colors.white,
child: new Center(
child: new Column(
mainAxisSize: MainAxisSize.min,
crossAxisAlignment: CrossAxisAlignment.center,
children: <Widget>[
new Icon(choice.icon, size: 128.0, color: textStyle.color),
new Text(choice.title, style: textStyle),
],
),
),
);
}
}
void main() {
runApp(new BasicAppBarSample());
}
See also:
- The “Layout-Structure” section of the Material Design specification: https://material.io/guidelines/layout/structure.html#structure-app-bar
- The source code in examples/catalog/lib/basic_app_bar.dart.