Retrofit 2.0使用

1.添加依赖

app/build.gradle文件中dependencies标签下，添加：

compile 'com.squareup.retrofit2:retrofit:2.3.0'

2.接口API

网络接口用的是和风天气的免费接口

定义接口

public interface ApiService {

    //url实例：https://free-api.heweather.com/v5/weather?city=yourcity&key=yourkey
    //正常的网络请求api,@Query参数会直接显示在url里
    @GET("weather")
    Call<ResponseBody> getWeather(@Query("city") String city, @Query("key") String key);

}

3.异步调用接口

//自己注册后的key
private static final String KEY = "124***fasdf****dcf*****3";

//创建Retrofit对象，设置baseUrl，Retrofit2.0的baseurl需要`/`结尾
Retrofit retrofit = new Retrofit.Builder()
        .baseUrl("https://free-api.heweather.com/v5/")
        .build();

//接口调用api，传入查询的参数
ApiService apiService = retrofit.create(ApiService.class);
Call<ResponseBody> call = apiService.getWeather("上海", KEY);
//同步用call.execute();
call.enqueue(new Callback<ResponseBody>() {
            @Override
            public void onResponse(Call<ResponseBody> call, Response<ResponseBody> response) {
                try {
                    Log.i("test", "result = \n" + response.body().string());
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            @Override
            public void onFailure(Call<ResponseBody> call, Throwable t) {
                Log.i("test", "onFailure");
            }
        });

//请求移除用call.cancel();

4.@Path和@Query

2中使用的是@Query，直接显示在url的查询条件，还可以通过变量控制url路径的@Path

使用@Path

//url中的变量用{}包括，并且与@Paht中声明的值相同
@GET("{user_name}/article/details/{blog_id}")
Call<ResponseBody> getBLog(@Path("user_name") String userName, @Path("blog_id") String blogId);

5.POST方式提交，用@Body 包装表单数据类

首先要添加转化Gson的支持，可直接将@Body 表示的类封装成json数据。添加依赖：

compile 'com.squareup.retrofit2:converter-gson:2.0.2'

接着为retrofit添加转换工厂

Retrofit retrofit = new Retrofit.Builder()
        .baseUrl("https://xxxx.xxxx.com/user/")
        //添加Gson转换
        .addConverterFactory(GsonConverterFactory.create())
        .build();

接口api

比如某个登录接口

//注意是POST格式才能用@Body
@POST("login")
Call<ResponseBody> loginByBean(@Body LoginUser user);

定义的LoginUser

public class LoginUser {

    //用@SerializedName() 可以指明json转换时候的字段名字
    @SerializedName("name")
    private String user_name;
    @SerializedName("password")
    private String user_password;
    @SerializedName("check")
    private String checkCode;


    public LoginUser(String user_name, String user_password, String checkCode) {
        this.user_name = user_name;
        this.user_password = user_password;
        this.checkCode = checkCode;
    }

    //setter and getter
    ...
}

异步调用发起请求

//直接传入LoginUser对象
apiService.loginByBean(new LoginUser("jack", "123123", "asdf"))
        .enqueue(new Callback<ResponseBody>() {
            @Override
            public void onResponse(Call<ResponseBody> call, Response<ResponseBody> response) {
                try {
                    Log.i("test", "by body ,result = \n" + response.body().string());
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            @Override
            public void onFailure(Call<ResponseBody> call, Throwable t) {
                Log.i("test", "onFailure");
            }
        });

添加gons转换后，还可以直接将返回的结果类型变为需要的类型。

api接口

//泛型直接指定为Weather
@GET("weather")
Call<Weather> getWeatherToWeatherBean(@Query("city") String city, @Query("key") String key);

创建Weather类，可使用AndroidStudio插件GsonFormat快速将json数据准换成java类。

最后调用

Call<Weather> call = apiService.getWeatherToWeatherBean("上海", KEY);
call.enqueue(new Callback<Weather>() {
    @Override
    public void onResponse(Call<Weather> call, Response<Weather> response) {
    //可以直接.getHeWeather5()然后调用类成员
        Log.i("test", "to weather bean : " + response.body()
                .getHeWeather5().get(0).getAqi().toString());
    }
    @Override
    public void onFailure(Call<Weather> call, Throwable t) {
    }
});

6.添加CallAdapter工厂，使用RxJava

添加依赖：

compile 'io.reactivex.rxjava2:rxjava:2.1.1'
compile 'io.reactivex.rxjava2:rxandroid:2.0.1'

然后给retrofit添加Rxjava工厂

Retrofit retrofit = new Retrofit.Builder()
        .baseUrl("https://free-api.heweather.com/v5/")
        //gons转换工厂
        .addConverterFactory(GsonConverterFactory.create())
        //rxjava-calladapter工厂
        .addCallAdapterFactory(RxJava2CallAdapterFactory.create())
        .build();

API接口更改：

//注意 Call换成了OBservable被观察者
@GET("weather")
Observable<Weather> getWeatherByRxjava(@Query("city") String city, @Query("key") String key);

最后调用

Observable<Weather> call = apiService.getWeatherByRxjava("上海", KEY);
//异步网络访问，在io线程（子线程）
call.subscribeOn(Schedulers.io())
        //回到主线程更新UI
        .observeOn(AndroidSchedulers.mainThread())
        .subscribe(new Observer<Weather>() {
            @Override
            public void onSubscribe(@NonNull Disposable d) {
                Log.i("test", "onSubscribe");
            }
            @Override
            public void onNext(@NonNull Weather weather) {
                Log.i("test", "rxjava result = " + weather.getHeWeather5()
                .get(0).getAqi().toString());
            }
            @Override
            public void onError(@NonNull Throwable e) {
                Log.i("test", "onError");
            }
            @Override
            public void onComplete() {
                Log.i("test", "onComplete");
            }
        });

7.打印请求地址和返回内容

使用Retrofit网络请求，需要使用到HttpLoggingInterceptor类，首先要添加依赖：

compile 'com.squareup.okhttp3:logging-interceptor:3.8.1'

然后初始化HttpLoggingInterceptor类：

HttpLoggingInterceptor loggingInterceptor = new HttpLoggingInterceptor(new HttpLoggingInterceptor.Logger() {
    @Override
    public void log(String message) {
        //打印retrofit日志
        Log.i("test", "back = " + message);
    }
});
//设置打印的等级
loggingInterceptor.setLevel(HttpLoggingInterceptor.Level.BODY);

打印的等级有：NONE、BASIC、HEADERS、BODY

接着配置okhttp的client：

OkHttpClient client = new OkHttpClient.Builder()
        //加入打印类loggingInterceptor
        .addInterceptor(loggingInterceptor)
        .connectTimeout(2000, TimeUnit.SECONDS)
        .readTimeout(2000, TimeUnit.SECONDS)
        .writeTimeout(2000, TimeUnit.SECONDS)
        .build();

最后创建Retrofit的时候配置进去：

Retrofit retrofit = new Retrofit.Builder()
        .baseUrl("https://free-api.heweather.com/v5/")
        .addConverterFactory(GsonConverterFactory.create())
        .addCallAdapterFactory(RxJava2CallAdapterFactory.create())
        //将定义的okhttp配置进入retrofit中
        .client(client)
        .build();