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• 配套视频

• 开始在build.gradle添加依赖

     compile 'io.reactivex:rxjava:1.0.9'   compile 'io.reactivex:rxandroid:0.24.0'   compile 'com.squareup.retrofit:retrofit:1.9.0'

• 需要的权限

      <uses-permission android:name="android.permission.INTERNET" />

• 使用RxjavaUtil请求数据时需要和Retrofit连用，第一步就是使用Retrofit定义所有功能接口的API服务类，以天气接口为例。，

接口地址：http://api.openweathermap.org/data/2.5/weather?q=shenzhen&mode=json&APPID=6c113432fd84a6e28268af291821db16

• 参数声明，Url都通过Annotation指定，接口定义如下：

    private interface AppApi {      @GET("/weather")      WeatherData getWeather(@Query("q") String city, @Query("mode") String mode, @Query("APPID") String APPID);  }

• 返回数据如下，可以使用GsonFormat自动生成javabean（即WeatherData)：

    {"coord":{"lon":114.07,"lat":22.55},"weather":[{"id":800,"main":"Clear","description":"clear sky","icon":"01n"}],"base":"stations","main":{"temp":293.15,"pressure":1018,"humidity":72,"temp_min":293.15,"temp_max":293.15},"visibility":10000,"wind":{"speed":3.69,"deg":116.004},"clouds":{"all":0},"dt":1483538400,"sys":{"type":1,"id":7420,"message":0.0134,"country":"CN","sunrise":1483484686,"sunset":1483523588},"id":1795565,"name":"Shenzhen","cod":200}

• 第二步是通过RestAdapter生成API接口服务的实现类(动态代理)

    private static final RestAdapter restAdapter = new RestAdapter.Builder().setEndpoint(ENDPOINT).setLogLevel(RestAdapter.LogLevel.FULL).build();  private static final AppApi appService = restAdapter.create(AppApi.class);

• 第三步是关键的一步，将返回的数据类型包装到一个数据源（Observable）中。onNext是RxJava发送事件，即开始请求数据，onCompleted为结束任务的事件，subscribeOn为指定获取数据的线程为耗时线程。

    public static Observable<WeatherData> getWeatherData(final String city) {  return Observable.create(new Observable.OnSubscribe<WeatherData>() {      @Override      public void call(Subscriber<? super WeatherData> subscriber) {          subscriber.onNext(appService.getWeather(city,"json", "6c113432fd84a6e28268af291821db16"));          subscriber.onCompleted();      }  }).subscribeOn(Schedulers.io());

  }

• 最后调用封装好的方法就可以了，拿到数据后，在主线程中回调（subscribeOn(Schedulers.io()），获取单个天气示例如下：

    RxJavaUtil.getWeatherData(cityName).subscribeOn(Schedulers.io())          .observeOn(AndroidSchedulers.mainThread())          .subscribe(new Action1<WeatherData>() {              @Override              public void call(WeatherData weatherData) {                  Log.d(LOG_TAG, weatherData.toString());                  switch (cityName){                      case "beijing":                          mTv1.setText(weatherData.toString());                          break;                      case "shenzhen":                          mTv2.setText(weatherData.toString());                          break;                      case "shanghai":                          mTv3.setText(weatherData.toString());                          break;                  }              }          }, new Action1<Throwable>() {              @Override              public void call(Throwable throwable) {                  Log.e(LOG_TAG, throwable.getMessage(), throwable);              }          });

• 当获取多个天气时候，要使用到Rxjava的变换，简单点理解，就是一个数据源变成多个数据源，一对多的映射关系。

    Observable.from(cities).flatMap(new Func1<String, Observable<WeatherData>>() {      @Override      public Observable<WeatherData> call(String city) {          return RxJavaUtil.getWeatherData(city);      }  }).subscribeOn(Schedulers.io())          .observeOn(AndroidSchedulers.mainThread())          .subscribe(/*onNext*/new Action1<WeatherData>() {              @Override              public void call(WeatherData weatherData) {                  String  cityName = weatherData.name.toLowerCase();                  switch (cityName){                      case "beijing":                          mTv1.setText(weatherData.toString());                          break;                      case "shenzhen":                          mTv2.setText(weatherData.toString());                          break;                      case "shanghai":                          mTv3.setText(weatherData.toString());                          break;                  }              }          }, /*onError*/new Action1<Throwable>() {              @Override              public void call(Throwable throwable) {              }          });}