编写简易Android天气应用的代码示例

本文所要介绍的简易天气App主要用RxAndroid、MVP、Retrofit实现，首先来看看效果：
主页内容：

右侧栏天气列表：

左侧栏城市列表

首先看看Activity主要代码（使用MVP模式）：

//调用Presenter的方法获取数据 
mMainPresenter = new MainPresenterImpl(this); 
mMainPresenter.getPlaceData(); 
mMainPresenter.getWeatherData("成都"); 

//显示主页和右侧栏天气数据 
public void setupWeatherData(WeatherResponse weatherResponse) { 
  if (weatherResponse == null) return; 
  setTitleText(DateUtils.getWeekDay(weatherResponse.date)); 
  if (weatherResponse.results != null && weatherResponse.results.size() > 0) { 
    WeatherResult result = weatherResponse.results.get(0); 
    mTvCity.setText(getString(R.string.city, result.currentCity)); 
    mTvPm25.setText(getString(R.string.pm25, result.pm25)); 
 
    mWeatherDataAdapter.setData(result.weather_data); 
    mWeatherDataAdapter.notifyDataSetChanged(); 
 
    mWeatherExtraAdapter.setData(result.index); 
    mWeatherExtraAdapter.notifyDataSetChanged(); 
  } 
} 

//显示左侧栏城市列表 
@Override 
public void setupPlaceData(List placeList) { 
  if (placeList == null) { 
    return; 
  } 
  mPlaceAdapter.setData(placeList); 
  mPlaceAdapter.notifyDataSetChanged(); 
} 

接下来看看如何在Presenter中应用RxJava、RxAndroid获取数据

//获取天气数据 
@Override 
public void getWeatherData(String place) { 
  if (TextUtils.isEmpty(place)) { 
    return; 
  } 
  mMainView.showProgress(); 
  ServiceManager.getInstance().getApiService().getWeatherInfo(place, Constants.BAIDU_AK) 
      .subscribeOn(Schedulers.io()) 
      .observeOn(AndroidSchedulers.mainThread()) 
      .subscribe(new Subscriber() { 
 @Override 
 public void onCompleted() { 
   Log.e(TAG, "onCompleted"); 
   mMainView.hideProgress(); 
 } 
 
 @Override 
 public void onError(Throwable e) { 
   Log.e(TAG, e.getMessage(), e); 
   mMainView.hideProgress(); 
 } 
 
 @Override 
 public void onNext(WeatherResponse weatherResponse) { 
   mMainView.setupWeatherData(weatherResponse); 
 } 
      }); 
} 

public interface ApiService { 
 
   
 
  @GET("service/getIpInfo.php") 
  Observable getIpInfo(@Query("ip") String ip); 
 
 
  //http://api.map.baidu.com/telematics/v3/weather?location=%E6%88%90%E9%83%BD&output=json&ak=MPDgj92wUYvRmyaUdQs1XwCf 
  @GET("/telematics/v3/weather?output=json") 
  Observable getWeatherInfo(@Query("location") String location, @Query("ak") String ak); 
} 

如上所述，我们通过百度api获取天气数据使用的是Retrofit框架，它能自动的返回Observable对象。
那么我们如何通过RxJava获取本地文件中的城市列表呢?（为了方便演示，我将城市列表作为一个json字符串放于文件中)

@Override 
public void getPlaceData() { 
  PlaceRepository repository = new PlaceRepository(); 
  repository.getPlaceList(baseApplication.getInstance()) 
      .subscribeOn(Schedulers.io()) 
      .observeOn(AndroidSchedulers.mainThread()) 
      .subscribe(new Subscriber>() { 
 @Override 
 public void onNext(List places) { 
   mMainView.setupPlaceData(places); 
 } 
 
 @Override 
 public void onCompleted() { 
 
 } 
 
 @Override 
 public void onError(Throwable e) { 
 
 } 
      }); 
} 

public class PlaceRepository { 
 
  public Observable> getPlaceList(final Context context) { 
    return Observable.create(new Observable.OnSubscribe>() { 
      @Override 
      public void call(Subscriber> subscriber) { 
 try { 
   AssetManager assertManager = context.getAssets(); 
   InputStream inputStream = assertManager.open("place"); 
   ByteArrayOutputStream outStream = new ByteArrayOutputStream(); 
   byte[] data = new byte[1024]; 
   int count = -1; 
   while((count = inputStream.read(data,0, 1024)) != -1) { 
     outStream.write(data, 0, count); 
   } 
   String json = new String(outStream.toByteArray(),"UTF-8"); 
   Gson gson = new GsonBuilder().create(); 
   List placeList = gson.fromJson(json, new TypeToken>() {}.getType()); 
   subscriber.onNext(placeList); 
 } catch (Exception e) { 
   subscriber.onError(e); 
 } 
 subscriber.onCompleted(); 
      } 
    }); 
  } 
} 

通过上述代码，我们就能完成界面所示功能了，是不是省去了Handler callback，new Thread()这些操作了，这就为什么说RxJava是用来解决Callback Hell的。

 ”在Activity中分别调用了获取天气数据和城市列表的方法，那么问题来了，如果取数据的时候显示了process Dialog, 我该在什么时候结束呢，写flag判断？“

     最直接的最暴力的方法就是直接在一个方法里同步调用两个接口，那使用RxJava怎么实现呢？

     这个问题可以使用RxJava的Merge操作符实现，故名思议就是将两个接口Observable合成一个，废话不说直接上代码：

@Override 
public void getPlaceAndWeatherData(String place) { 
  mMainView.showProgress(); 
  PlaceRepository repository = new PlaceRepository(); 
  Context context = baseApplication.getInstance(); 
  Observable placeObservable = repository.getPlaceList(context); 
  Observable weatherObservable = ServiceManager.getInstance().getApiService().getWeatherInfo(place, Constants.BAIDU_AK); 
  Observable.merge(placeObservable, weatherObservable) 
      .subscribeOn(Schedulers.io()) 
      .observeOn(AndroidSchedulers.mainThread()) 
      .subscribe(new Subscriber