Flutter实战1 --- 写一个天气查询的APP,android游戏开发大全第二版代码

),
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{
@override
State createState() {
// TODO: implement createState
return new WeatherState();
}
}

class WeatherState extends State{
@override
Widget build(BuildContext context) {
// TODO: implement build
return 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.
@override
Widget 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+scmd+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: true
assets:

  • images/

4.4 写WeatherWidget的UI布局

Scaffold中添加body的属性,来写UI的布局,如下:

class WeatherState extends State{
@override
Widget build(BuildContext context) {
// TODO: implement build
return Scaffold(
body: new Stack(
fit: StackFit.expand,
children: [
new Image.asset(“images/weather_bg.jpg”,fit: BoxFit.fitHeight,),
new Column(
mainAxisAlignment: MainAxisAlignment.start,
crossAxisAlignment: CrossAxisAlignment.center,
children: [
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: [
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
),
)
],
),
)
],
)
],
),
);
}

}

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: ^0.1.2
http: ^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。

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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

WeatherData({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{

WeatherData weather = WeatherData.empty();

WeatherState(){
_getWeather();
}

void _getWeather() async{
WeatherData data = await _fetchWeather();
setState((){
weather = data;
});
}

Future _fetchWeather() async{
final response = await http.get(‘https://free-api.heweather.com/s6/weather/now?location=广州&key=ebb698e9bb6844199e6fd23cbb9a77c5’);
if(response.statusCode == 200){
return WeatherData.fromJson(json.decode(response.body));
}else{
return WeatherData.empty();
}
}

@override

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