Android 开源项目学习之Retrofit2.0使用篇

引入Retrofit 相关的库

compile 'io.reactivex:rxjava:1.1.0'      //RxJava 相关
compile 'io.reactivex:rxandroid:1.1.0'   //RxJava 相关
compile 'com.squareup.retrofit2:adapter-rxjava:2.0.0-beta4'  //Retrofit Rxjava Adapter
compile 'com.squareup.retrofit2:retrofit:2.0.0-beta4'        //Retrofit 
compile 'com.squareup.retrofit2:converter-gson:2.0.0-beta4'  //Gson Adapter
compile 'com.google.code.gson:gson:2.6.2'                    //Gson

定义 Api 接口
一个Service是一个接口如下所示，它一般指定了http方式是一个get还是post方式，以及一个相对的路径。

public interface OpenWeatherApi {
    @GET("weather")
    Call<WeatherResult> getCityWeather(@Query("id") String id,@Query("appid") String ApiId);
}

使用注释来创建url
这个方面请大家看下这篇博客，个人认为总结得十分全面，所以就直接转过来了：
http://blog.csdn.net/stven_king/article/details/52372172
最常使用的请求方式：
@GET @POST
请求url相关的注释：
@Query，@QueryMap，@Field，@FieldMap，@FormUrlEncoded，@Path，@Url

( 1 ) GET 请求方式：

public interface GitHubService {//无参数@GET("users/stven0king/repos")
    Call<List<Repo>> listRepos();
    //少数参数@GET("users/stven0king/repos")
    Call<List<Repo>> listRepos(@Query("time") long time);
    //参数较多@GET("users/stven0king/repos")
    Call<List<Repo>> listRepos(@QueryMap Map<String, String> params);
}

( 2 ) POST 请求方式：

public interface GitHubService {//无参数@POST("users/stven0king/repos")
    Call<List<Repo>> listRepos();
    //少数参数@FormUrlEncoded@POST("users/stven0king/repos")
    Call<List<Repo>> listRepos(@Field("time") long time);
    //参数较多@FormUrlEncoded@POST("users/stven0king/repos")
    Call<List<Repo>> listRepos(@FieldMap Map<String, String> params);
}

@POST @GET多了一个@FromUrlEncoded的注解。如果去掉@FromUrlEncoded在post请求中使用@Field和@FieldMap，那么程序会抛出Java.lang.IllegalArgumentException: @Field parameters can only be used with form encoding. (parameter #1)的错误异常。

( 3 ) 半静态的url 地址请求：

public interface GitHubService {@GET("users/{user}/repos")
  Call<List<Repo>> listRepos(@Path("user") String user);
}

( 4 ) 动态的url地址请求：

public interface GitHubService {@GET
  Call<List<Repo>> listRepos(@Url String user);
}

创建retrofit对象

Retrofit retrofit = new Retrofit.Builder()
        .baseUrl("http://api.openweathermap.org/data/2.5/")
        .addConverterFactory(GsonConverterFactory.create())
        .build();

在Retrofit 2.0中，需要我们自己引入Converter 不然的话Retrofit 只能接收字符串结果，下面是retrofit 支持的json converter

Gson: com.squareup.retrofit:converter-gson
Jackson: com.squareup.retrofit:converter-jackson
Moshi: com.squareup.retrofit:converter-moshi
Protobuf: com.squareup.retrofit:converter-protobuf
Wire: com.squareup.retrofit:converter-wire
Simple XML: com.squareup.retrofit:converter-simplexml

使用retrofit对象来创建对应的API接口：

OpenWeatherApi mWeatherService = retrofit.create(OpenWeatherApi.class);

5.使用上面创建的API接口来访问对应的服务：
（这里为了安全所以我这边用了一个伪appid，大家可以自己申请然后替换）

Call<WeatherResult> resultCall = mWeatherService.getCityWeather("1790437","f8ddddd63c40c0bcb89");
resultCall.enqueue(new Callback<WeatherResult>() {
    @Override
    public void onResponse(Call<WeatherResult> call, Response<WeatherResult> response) {
        if(response.body() == null) {
            Log.i("xiaohai.lin","Request Failed Response Code = "+ response.code());
            return;
        }
        Log.i("xiaohai.lin","Templete = "+response.body().getMain().getTemp());
        Log.i("xiaohai.lin","getDescription = "+response.body().getWeather().get(0).getDescription());
    }
    @Override
    public void onFailure(Call<WeatherResult> call, Throwable t) {}
});

异步请求

resultCall.enqueue(new Callback<WeatherResult>() {
    @Override
    public void onResponse(Call<WeatherResult> call, Response<WeatherResult> response) {
        if(response.body() == null) {
            Log.i("xiaohai.lin","Request Failed Response Code = "+ response.code());
            return;
        }
        Log.i("xiaohai.lin","Templete = "+response.body().getMain().getTemp());
        Log.i("xiaohai.lin","getDescription = "+response.body().getWeather().get(0).getDescription());
    }
    @Override
    public void onFailure(Call<WeatherResult> call, Throwable t) {}
});

以上代码发起了一个在后台线程的请求并从response 的response.body()方法中获取一个结果对象。这里onResponse和onFailure方法是在主线程中调用的。

同步请求
同步请求需要调用execute方法，但是由于同步方式会阻塞线程所以不能在主线程中调用。否则会遇到NetworkOnMainThreadException异常。

new AsyncTask<String, Integer, Response<WeatherResult>>(){
    @Override
    protected Response<WeatherResult> doInBackground(String... params) {
        if(params == null|| params[0] == null||params[1]== null) {
            return null;
        }
        Retrofit retrofit = new Retrofit.Builder()
                .baseUrl("http://api.openweathermap.org/data/2.5/")
                .addConverterFactory(GsonConverterFactory.create())
                .build();
        OpenWeatherApi mWeatherService = retrofit.create(OpenWeatherApi.class);
        final Call<WeatherResult> resultCall = mWeatherService.getCityWeather(params[0],params[1]);
        Response<WeatherResult> result = null;
        try {
            result = resultCall.execute();
        } catch (IOException e) {
            e.printStackTrace();
        }
        return result;
    }
    @Override
    protected void onPostExecute(Response<WeatherResult> response) {
        if(response == null || response.body() == null) {
            return;
        }
        Log.i("xiaohai.lin","Templete = "+response.body().getMain().getTemp());
        Log.i("xiaohai.lin","getDescription = "+response.body().getWeather().get(0).getDescription());
    }
}.execute("1790437","f8ddddcb89");

8 取消正在进行中访问

call.cancel();

9 获取结果的处理

在Retrofit 1.9中，如果获取的 response 不能被解析成定义好的对象，则会调用failure。但是在Retrofit 2.0中，不管 response 是否能被解析。onResponse总是会被调用。但是在结果不能被解析的情况下，response.body()会返回null。

如果response存在什么问题，onResponse也会被调用。我们可以从response.errorBody().string()中获取错误信息的主体。

10 Retrofix 结合 Rxjava

public interface OpenWeatherApis {
    @GET("weather")
    Observable<WeatherResult> getCityWeather(@Query("id") String id, @Query("appid") String ApiId);
}

Retrofit retrofit = new Retrofit.Builder()
        .baseUrl("http://api.openweathermap.org/data/2.5/")
        .addConverterFactory(GsonConverterFactory.create())
        .addCallAdapterFactory(RxJavaCallAdapterFactory.create())
        .build();

OpenWeatherApis openWeatherApis = retrofit.create(OpenWeatherApis.class);
Observable<WeatherResult> result = openWeatherApis.getCityWeather("1790437","f8d8edded5c40c0bcbdd89");
result.observeOn(AndroidSchedulers.mainThread())
        .subscribeOn(Schedulers.io())
        .subscribe(new Action1<WeatherResult>() {
            @Override
            public void call(WeatherResult weatherResult) {
                Log.i("xiaohai.lin","Templete = "+weatherResult.getMain().getTemp());
                Log.i("xiaohai.lin","getDescription = "+weatherResult.getWeather().get(0).getDescription());
            }
        });

11 添加log支持

HttpLoggingInterceptor httpLoggingInterceptor = new HttpLoggingInterceptor();
httpLoggingInterceptor.setLevel(HttpLoggingInterceptor.Level.BODY);
OkHttpClient okHttpClient = new OkHttpClient.Builder()
        .addInterceptor(httpLoggingInterceptor)
        .build();

Retrofit retrofit = new Retrofit.Builder()
        .baseUrl("http://api.openweathermap.org/data/2.5/")
        .addConverterFactory(GsonConverterFactory.create())
        .client(okHttpClient)
        .build();
OpenWeatherApi mWeatherService = retrofit.create(OpenWeatherApi.class);
final Call<WeatherResult> resultCall = mWeatherService.getCityWeather("1790437","f8d8ead8299f963abcded5c40c0bcb89");
resultCall.enqueue(new Callback<WeatherResult>() {
    @Override
    public void onResponse(Call<WeatherResult> call, Response<WeatherResult> response) {

        if(response.body() == null) {
            Log.i("xiaohai.lin","Request Failed Response Code = "+ response.code());
            return;
        }
        Log.i("xiaohai.lin","Templete = "+response.body().getMain().getTemp());
        Log.i("xiaohai.lin","getDescription = "+response.body().getWeather().get(0).getDescription());
    }

    @Override
    public void onFailure(Call<WeatherResult> call, Throwable t) {

    }
});

11 Retrofix 结合 Realm:

Realm 是我个人的喜好，是用得最爽的一个nosql类型的数据库，没有之一。
Realm 可以与 Retrofit 1.x 和 2.x 无缝配合工作。但注意 Retrofit 不会自动将对象存入 Realm。
需要通过调用 Realm.copyToRealm() 或 Realm.copyToRealmOrUpdate() 来将它们存入 Realm。

realm.beginTransaction();
WeatherResult realmWhether = realm.copyToRealmOrUpdate(result);
realm.commitTransaction();