),
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+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: true
assets:
- 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{
@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
),
)
],
),
)
],
)
],
),
);
}
}
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: ^0.1.2
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