Flutter开发体验-新建项目到运行项目

准备工作

开发环境：

设备：mac电脑
开发工具：Visual Studio Code 版本1.57.0
其他工具：Android Studio、Xcode、Chrome
插件：Visual Studio Code安装Flutter插件，Flutter使用的是Dart语言，安装了Flutter插件，自带就下载了Dart插件

接下来，开始体验Flutter的开发之旅吧！

新建项目

快捷键：shift+comman+P，新建flutter项目

新建项目

目录结构看下图：

目录结构

作为初学者，目前我们主要看这两个文件，main.dart和pubspec.yaml，main.dart是项目的初始化入口，根组件设置主要在这个文件里，体验flutter开发的代码主要在这里写；pubspec.yaml主要是flutter开发的配置文件，里面包含项目的信息、SDK版本、第三方package依赖，以后的开发过程中，我们肯定会用到很多第三方的组件，这里添加第三方组件也很简单，如下图：

配置文件

在dependencies下添加第三方组件，cupertino_icons就是新建flutter项目时自带的一个第三方组件，后面是它的版本号，这里版本号有不同的设置方法，后面另说。

现在来说说main.dart文件的代码结构：

import 'package:flutter/material.dart';

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

class MyApp extends StatelessWidget {
  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        // This is the theme of your application.
        //
        // Try running your application with "flutter run". You'll see the
        // application has a blue toolbar. Then, without quitting the app, try
        // changing the primarySwatch below to Colors.green and then invoke
        // "hot reload" (press "r" in the console where you ran "flutter run",
        // or simply save your changes to "hot reload" in a Flutter IDE).
        // Notice that the counter didn't reset back to zero; the application
        // is not restarted.
        primarySwatch: Colors.blue,
      ),
      home: MyHomePage(title: 'Flutter Demo Home Page'),
    );
  }
}

class MyHomePage extends StatefulWidget {
  MyHomePage({Key? key, required this.title}) : super(key: key);

  // This widget is the home page of your application. It is stateful, meaning
  // that it has a State object (defined below) that contains fields that affect
  // how it looks.

  // This class is the configuration for the state. It holds the values (in this
  // case the title) provided by the parent (in this case the App widget) and
  // used by the build method of the State. Fields in a Widget subclass are
  // always marked "final".

  final String title;

  @override
  _MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State {
  int _counter = 0;

  void _incrementCounter() {
    setState(() {
      // This call to setState tells the Flutter framework that something has
      // changed in this State, which causes it to rerun the build method below
      // so that the display can reflect the updated values. If we changed
      // _counter without calling setState(), then the build method would not be
      // called again, and so nothing would appear to happen.
      _counter++;
    });
  }

  @override
  Widget build(BuildContext context) {
    // This method is rerun every time setState is called, for instance as done
    // by the _incrementCounter method above.
    //
    // The Flutter framework has been optimized to make rerunning build methods
    // fast, so that you can just rebuild anything that needs updating rather
    // than having to individually change instances of widgets.
    return Scaffold(
      appBar: AppBar(
        // Here we take the value from the MyHomePage object that was created by
        // the App.build method, and use it to set our appbar title.
        title: Text(widget.title),
      ),
      body: Center(
        // Center is a layout widget. It takes a single child and positions it
        // in the middle of the parent.
        child: Column(
          // Column is also a layout widget. It takes a list of children and
          // arranges them vertically. By default, it sizes itself to fit its
          // children horizontally, and tries to be as tall as its parent.
          //
          // Invoke "debug painting" (press "p" in the console, choose the
          // "Toggle Debug Paint" action from the Flutter Inspector in Android
          // Studio, or the "Toggle Debug Paint" command in Visual Studio Code)
          // to see the wireframe for each widget.
          //
          // Column has various properties to control how it sizes itself and
          // how it positions its children. Here we use mainAxisAlignment to
          // center the children vertically; the main axis here is the vertical
          // axis because Columns are vertical (the cross axis would be
          // horizontal).
          mainAxisAlignment: MainAxisAlignment.center,
          children: [
            Text(
              'You have pushed the button this many times:123',
            ),
            Text(
              '$_counter',
              style: Theme.of(context).textTheme.headline4,
            ),
          ],
        ),
      ),
      floatingActionButton: FloatingActionButton(
        onPressed: _incrementCounter,
        tooltip: 'Increment',
        child: Icon(Icons.add),
      ), // This trailing comma makes auto-formatting nicer for build methods.
    );
  }
}

void main() {}是项目初始化的主入口
class MyApp extends StatelessWidget {}是自定义的一个无状态组件，默认会有一个build方法；
class MyHomePage extends StatefulWidget {}是自定义的一个有状态的组件，默认会有class _MyHomePageState extends State {}State类。

运行

了解完上面的基本结构，现在我们看看如何运行代码，如下图：

运行方法

选择设备

运行结果：

运行结果

现在，我们可以体验一下flutter的另一个高效开发的技能：热重载，随意修改代码中文本上的内容，保存就可以看到页面上已动态刷新的内容。

结语

好了，以上就是从新建项目到运行第一个项目的过程，如有问题，欢迎指正哦！

题外话：虽然网上教程很多，写的比我全面以及好的多，但个人觉得有古话说的好：好记性不如烂笔头，以自己的理解记录下学习的过程是一个很好的学习方法，若有问题，欢迎指正，必认真修改！愿与大家共勉~

参考：
https://flutterchina.club/get-started/codelab/