Flutter 2.创建app

1.创建项目 运行

import 'package:flutter/material.dart';

void main() => runApp(new MyApp());

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return new MaterialApp(
      title: 'Welcome to Flutter',
      home: new Scaffold(
        appBar: new AppBar(
          title: new Text('Welcome to Flutter'),
        ),
        body: new Center(
          child: new Text('Hello World'),
        ),
      ),
    );
  }
}

main函数使用了(=>)符号, 这是Dart中单行函数或方法的简写。

void main() => runApp(new MyApp());

等价于

void main() {
  runApp(new MyApp());
}

创建app 继承 StatelessWidget

class MyApp extends StatelessWidget {

Scaffold 是 Material library 中提供的一个widget, 它提供了默认的导航栏、标题和包含主屏幕widget树的body属性。widget树可以很复杂。

widget的主要工作是提供一个build()方法来描述如何根据其他较低级别的widget来显示自己。

本示例中的body的widget树中包含了一个Center widget, Center widget又包含一个 Text 子widget。 Center widget可以将其子widget树对其到屏幕中心。

2 更改 AppBar

 

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return new MaterialApp(
      title: 'Welcome to Flutter',
      home: new Scaffold(
        appBar: new AppBar(
          title: new Text("Flutter"),
          actions: <Widget>[
            new IconButton(icon: new Icon(Icons.add_alert), onPressed: (){ _pressed("add_alert"); }),

            new IconButton(icon: new Icon(Icons.print), onPressed: (){ _pressed("print"); }),
            new IconButton(icon: new Icon(Icons.people), onPressed: (){ _pressed("people"); }),
            
          ],
        ),
        body: new Center(
          child: new Text('Hello World'),
        ),
      ),
    );
  }

3 pubspec.yaml

name: flutterdemo
description: A new Flutter project.

dependencies:
  flutter:
    sdk: flutter


  # 国际化
  flutter_localizations:
    sdk: flutter
  intl:
  intl_translation:

  # The following adds the Cupertino Icons font to your application.
  # Use with the CupertinoIcons class for iOS style icons.
  cupertino_icons: ^0.1.0

  # Use an external package
  english_words: ^3.1.0

dev_dependencies:
  flutter_test:
    sdk: flutter


# For information on the generic Dart part of this file, see the
# following page: https://www.dartlang.org/tools/pub/pubspec

# The following section is specific to Flutter.
flutter:

  # The following line ensures that the Material Icons font is
  # included with your application, so that you can use the icons in
  # the material Icons class.
  uses-material-design: true

  # To add assets to your application, add an assets section, like this:
  # assets:
  #  - images/a_dot_burr.jpeg
  #  - images/a_dot_ham.jpeg

  # An image asset can refer to one or more resolution-specific "variants", see
  # https://flutter.io/assets-and-images/#resolution-aware.

  # For details regarding adding assets from package dependencies, see
  # https://flutter.io/assets-and-images/#from-packages

  # To add custom fonts to your application, add a fonts section here,
  # in this "flutter" section. Each entry in this list should have a
  # "family" key with the font family name, and a "fonts" key with a
  # list giving the asset and other descriptors for the font. For
  # example:
  # fonts:
  #   - family: Schyler
  #     fonts:
  #       - asset: fonts/Schyler-Regular.ttf
  #       - asset: fonts/Schyler-Italic.ttf
  #         style: italic
  #   - family: Trajan Pro
  #     fonts:
  #       - asset: fonts/TrajanPro.ttf
  #       - asset: fonts/TrajanPro_Bold.ttf
  #         weight: 700
  #
  # For details regarding fonts from package dependencies, 
  # see https://flutter.io/custom-fonts/#from-packages

源码 地址

https://github.com/kylinhuang/flutterDemo/blob/master/flutterdemo/lib/flutter1/flutterapp.dart