Flutter 实战 1 --- 写一个天气查询的 APP
https://free-api.heweather.com/s6/weather/now?location=广州 &key=******
4.界面编写
在创建的工程里,有个main.dart
里面有一段显示界面的代码如下:
class MyApp extends StatelessWidget {// This widget is the root of your application.@overrideWidget 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 press Run > Flutter 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'),);}}
其中home
就是要显示的界面,这里我们要把MyHomePage
换成我们自己的。
4.1 创建 WeatherWidget
通过 new
-> Dart File
在 lib 目录下创建 WeatherWidget
class WeatherWidget extends StatefulWidget{@overrideState<StatefulWidget> createState() {// TODO: implement createStatereturn new WeatherState();}}
class WeatherState extends State<WeatherWidget>{@overrideWidget build(BuildContext context) {// TODO: implement buildreturn Scaffold();}
}
创建完后,在main.dart
中将home
改为WeatherWidget
,如下:
class MyApp extends StatelessWidget {// This widget is the root of your application.@overrideWidget build(BuildContext context) {return MaterialApp(title: 'Flutter Demo',theme: ThemeData(primarySwatch: Colors.blue,),home: WeatherWidget(),);}
4.2 HotReload
在写 UI 的工程中,我们可以用到 Flutter 的 hot reload 的特性,写布局的时候,按ctrl+s
或cmd+s
就可以在手机上实时看到界面的变化。
这个功能很好用。
4.3 添加图片资源
Flutter 可以添加不同的资源,例如图片、文本、配置文件、静态数据等。
添加资源时,需要在pubspec.yaml
文件中的flutter
属性下添加assets
,并标明要添加资源的路径,例如,我们要加入指定的图片时,可以这么写:
flutter:assets:
assets/my_icon.png
assets/background.png
如果要添加的资源太多,也可以添加文件夹,例如:
flutter:assets:
assets/
在本 demo 中,要添加一个背景图,我们在工程的根目录下创建images
目录,将背景图放在images
目录下,然后在pubspec.yaml
中添加:
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: trueassets:
images/
4.4 写 WeatherWidget 的 UI 布局
在Scaffold
中添加body
的属性,来写 UI 的布局,如下:
class WeatherState extends State<WeatherWidget>{@overrideWidget build(BuildContext context) {// TODO: implement buildreturn Scaffold(body: new Stack(fit: StackFit.expand,children: <Widget>[new Image.asset("images/weather_bg.jpg",fit: BoxFit.fitHeight,),new Column(mainAxisAlignment: MainAxisAlignment.start,crossAxisAlignment: CrossAxisAlignment.center,children: <Widget>[new Container(width: double.infinity,margin: EdgeInsets.only(top: 40.0),child: new Text("广州市",textAlign: TextAlign.center,style: new TextStyle(color: Colors.white,fontSize: 30.0,),),),new Container(width: double.infinity,margin: EdgeInsets.only(top: 100.0),child: new Column(children: <Widget>[new Text("20 °",style: new TextStyle(color: Colors.white,fontSize: 80.0)),new Text("晴",style: new TextStyle(color: Colors.white,fontSize: 45.0)),new Text("湿度 80%",style: new TextStyle(color: Colors.white,fontSize: 30.0),)],),)],)],),);}
}
按ctrl+s
,在手机上就可以看到写好的 UI,但这时候的数据是写死的,下来看如何通过 http 获取数据。
5.通过 http 获取数据
要通过 http 数据,我们首先要添加 http 的依赖库,在pubspec.yaml
中的dependencies
添加如下:
dependencies:flutter:sdk: flutter
The following adds the Cupertino Icons font to your application.
Use with the CupertinoIcons class for iOS style icons.
cupertino_icons: ^0.1.2http: ^0.12.0
然后在当前工程目录下运行以下命令行:
$ flutter packages get
或者在 Android Stuido 打开pubspec.yaml
文件,点击上面的packages get
这里操作的意义是,拉取 http 的库。
5.1 创建 WeatherData 类
通过 new
-> Dart File
在 lib 目录下创建 WeatherData
class WeatherData{String cond; //天气 String tmp; //温度 String hum; //湿度
Weather
Data({this.cond, this.tmp, this.hum});
factory WeatherData.fromJson(Map<String, dynamic> json) {return WeatherData(cond: json['HeWeather6'][0]['now']['cond_txt'],tmp: json['HeWeather6'][0]['now']['tmp']+"°",hum: "湿度 "+json['HeWeather6'][0]['now']['hum']+"%",);}
factory WeatherData.empty() {return WeatherData(cond: "",tmp: "",hum: "",);}}
5.2 数据获取
class WeatherState extends State<WeatherWidget>{
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