Flutter第一个demo解析

之前是用终端创建的demo,下午下载安装了VS Code 这个轻量级的工具做另外的尝试!
VS code 下载链接
下载好后 安装插件 把上次下载的sdk导入VS code
步骤如下

View>Command Palette

输入 ‘install’, 然后选择 Extensions: Install Extension

在搜索框输入 flutter , 在搜索结果列表中选择 ‘Flutter’, 然后点击 Install

重新启动 VS Code

创建新应用

1 View>Command Palette…

2 输入 ‘flutter’, 然后选择 ‘Flutter: New Project’(注意项目不能有大写字母)
3 输入Project名字 我的命名为 app001
4 指定放置项目的位置，然后按蓝色的确定按钮

然后我们可以看到创建完成后的项目是这样的

2667FFBE-F9FD-49D5-9A6F-8A07B96873A7.png

在lib 文件夹下有个main.dart,这就是主页面的布局
里面的代码如下

import 'package:flutter/material.dart';

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

class MyApp extends StatelessWidget {
  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return new MaterialApp(
      title: 'Flutter Demo',
      theme: new 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 press Run > Flutter Hot Reload in IntelliJ). Notice that the
        // counter didn't reset back to zero; the application is not restarted.
        primarySwatch: Colors.blue,
      ),
      home: new MyHomePage(title: 'Flutter Demo Home Page'),
    );
  }
}

class MyHomePage extends StatefulWidget {
  MyHomePage({Key key, 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() => new _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 new Scaffold(
      appBar: new 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: new Text(widget.title),
      ),
      body: new Center(
        // Center is a layout widget. It takes a single child and positions it
        // in the middle of the parent.
        child: new Column(
          // Column is also 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 paint" (press "p" in the console where you ran
          // "flutter run", or select "Toggle Debug Paint" from the Flutter tool
          // window in IntelliJ) 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: [
            new Text(
            'You have pushed the button this many times:',
              //"我来了,我看见,我拥有",
            ),
            new Text(
              '$_counter',
              style: Theme.of(context).textTheme.display1,
            ),
          ],
        ),
      ),
      floatingActionButton: new FloatingActionButton(
        onPressed: _incrementCounter,
        tooltip: 'Increment',
        child: new Icon(Icons.add),
      ), // This trailing comma makes auto-formatting nicer for build methods.
    );
  }
}

这个文件里有布局容器 Widget 类似于iOS的UIView,具体的区别以后再说,有事件响应方法,有导航栏的设置等.
选择设备后 VS code 右下角会显示运行的设备

5EC931D7-C933-46D2-ACC4-3542B85D29E9.png

我们先去iOS的目录下配置证书,按F5或者Debug---start debug
会发现程序会在真机运行起来.效果如下

[图片上传中...(IMG_0623.PNG-8ca8dc-1538037858410-0)]

我们修改children里面的text的内容 再次运行

IMG_0623.PNG