Retrofit 快速学习

内容导图

1、依赖库导入

implementation 'com.squareup.retrofit2:retrofit:2.4.0'
implementation 'com.squareup.retrofit2:converter-gson:2.3.0'

2、基本使用

2.1、定义请求接口

import hq.demo.net.model.WeatherBeans;
import retrofit2.Call;
import retrofit2.http.Field;
import retrofit2.http.FormUrlEncoded;
import retrofit2.http.GET;
import retrofit2.http.POST;

public interface NetService {

    @GET("?app=weather.future&weaid=1&&appkey=10003&sign=b59bc3ef6191eb9f747dd4e83c99f2a4&format=json")
    Call<WeatherBeans> requestWeatherBeans();

    @POST("/")
    @FormUrlEncoded
    Call<WeatherBeans> requestWeatherBeans(
            @Field("app") String app,
            @Field("weaid") String weaid,
            @Field("appkey") String appkey,
            @Field("sign") String sign,
            @Field("format") String format);


}

这里要注意的是@FormUrlEncoded，如果post请求不加上它就会报错如下：java.lang.IllegalArgumentException: @Field parameters can only be used with form encoding. (parameter #1)for method NetService.requestWeatherBeans

为什么要加上这个注释，后面分析。

 

2.2、get请求网络数据

private void doGet() {

        Retrofit retrofit = new Retrofit.Builder()
                .baseUrl("http://api.k780.com/")
                .addConverterFactory(GsonConverterFactory.create())
                .build();
        NetService netService = retrofit.create(NetService.class);
        Call<WeatherBeans> call = netService.requestWeatherBeans();
        call.enqueue(new Callback<WeatherBeans>() {
            @Override
            public void onResponse(Call<WeatherBeans> call, Response<WeatherBeans> response) {


                if (response.isSuccessful()) {
                    WeatherBeans beans = response.body();
                    Log.d("######beans", beans.toString());
                    for (WeatherBeans.ResultBean bean : beans.getResult()) {
                        Log.d("cityName", bean.getCitynm());
                        Log.d("days", bean.getDays());
                    }
                }
            }

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

            }
        });
    }


结果：
09-07 22:05:32.537 8546-8546/hq.demo.net D/cityName: 北京
09-07 22:05:32.537 8546-8546/hq.demo.net D/days: 2018-09-05
09-07 22:05:32.537 8546-8546/hq.demo.net D/cityName: 北京
09-07 22:05:32.537 8546-8546/hq.demo.net D/days: 2018-09-06
09-07 22:05:32.537 8546-8546/hq.demo.net D/cityName: 北京
09-07 22:05:32.537 8546-8546/hq.demo.net D/days: 2018-09-07
09-07 22:05:32.538 8546-8546/hq.demo.net D/cityName: 北京
09-07 22:05:32.538 8546-8546/hq.demo.net D/days: 2018-09-08
09-07 22:05:32.538 8546-8546/hq.demo.net D/cityName: 北京
09-07 22:05:32.538 8546-8546/hq.demo.net D/days: 2018-09-09
09-07 22:05:32.538 8546-8546/hq.demo.net D/cityName: 北京
09-07 22:05:32.538 8546-8546/hq.demo.net D/days: 2018-09-10
09-07 22:05:32.538 8546-8546/hq.demo.net D/cityName: 北京
09-07 22:05:32.538 8546-8546/hq.demo.net D/days: 2018-09-11

2.3、post请求

private void doPost() {
        Retrofit retrofit = new Retrofit.Builder()
                .baseUrl("http://api.k780.com")
                .addConverterFactory(GsonConverterFactory.create())
                .build();
        NetService netService = retrofit.create(NetService.class);
        Call<WeatherBeans> call = netService.requestWeatherBeans("weather.future","1","10003","b59bc3ef6191eb9f747dd4e83c99f2a4","json");
        call.enqueue(new Callback<WeatherBeans>() {
            @Override
            public void onResponse(Call<WeatherBeans> call, Response<WeatherBeans> response) {


                if (response.isSuccessful()) {
                    WeatherBeans beans = response.body();
                    for (WeatherBeans.ResultBean bean : beans.getResult()) {
                        Log.d("cityName", bean.getCitynm());
                        Log.d("days", bean.getDays());
                    }
                }
            }

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

            }
        });
    }


结果：
09-07 22:11:37.351 8546-8546/hq.demo.net D/cityName: 北京
09-07 22:11:37.352 8546-8546/hq.demo.net D/days: 2018-09-05
09-07 22:11:37.352 8546-8546/hq.demo.net D/cityName: 北京
09-07 22:11:37.352 8546-8546/hq.demo.net D/days: 2018-09-06
09-07 22:11:37.352 8546-8546/hq.demo.net D/cityName: 北京
09-07 22:11:37.352 8546-8546/hq.demo.net D/days: 2018-09-07
09-07 22:11:37.352 8546-8546/hq.demo.net D/cityName: 北京
09-07 22:11:37.352 8546-8546/hq.demo.net D/days: 2018-09-08
09-07 22:11:37.352 8546-8546/hq.demo.net D/cityName: 北京
09-07 22:11:37.352 8546-8546/hq.demo.net D/days: 2018-09-09
09-07 22:11:37.352 8546-8546/hq.demo.net D/cityName: 北京
09-07 22:11:37.352 8546-8546/hq.demo.net D/days: 2018-09-10
09-07 22:11:37.352 8546-8546/hq.demo.net D/cityName: 北京
09-07 22:11:37.352 8546-8546/hq.demo.net D/days: 2018-09-11

因为：http://api.k780.com/?app=weather.future&weaid=1&&appkey=10003&sign=b59bc3ef6191eb9f747dd4e83c99f2a4&format=json是可以同时接受get/post请求的

2.4、步骤解析

使用retrofit从网络请求回来的数据采用gson数据解析，在通过建造者模式创建出Retrofit的时候回通过addConverterFactory添加一个GsonConverterFactory，GsonConverterFactory通过create()创建其实例，默认情况下会使用Gson，create()的重载方法create(Gson gson)，也是可以传入一个Gson实例的，

Retrofit retrofit = new Retrofit.Builder()
                .baseUrl("http://api.k780.com/")
                .addConverterFactory(GsonConverterFactory.create())
                .build();

NetService netService = retrofit.create(NetService.class);

然后Retrofit通过动态加载的将自定义的接口接管

public <T> T create(final Class<T> service) {
    Utils.validateServiceInterface(service);
    if (validateEagerly) {
      eagerlyValidateMethods(service);
    }
    return (T) Proxy.newProxyInstance(service.getClassLoader(), new Class<?>[] { service },
        new InvocationHandler() {
          private final Platform platform = Platform.get();

          @Override public Object invoke(Object proxy, Method method, @Nullable Object[] args)
              throws Throwable {
            // If the method is a method from Object then defer to normal invocation.
            if (method.getDeclaringClass() == Object.class) {
              return method.invoke(this, args);
            }
            if (platform.isDefaultMethod(method)) {
              return platform.invokeDefaultMethod(method, service, proxy, args);
            }
            ServiceMethod<Object, Object> serviceMethod =
                (ServiceMethod<Object, Object>) loadServiceMethod(method);
            OkHttpCall<Object> okHttpCall = new OkHttpCall<>(serviceMethod, args);
            return serviceMethod.callAdapter.adapt(okHttpCall);
          }
        });
  }

 

2.5、通过Call的实现类OKHttpCall与OKHttp进行网络请求

其实retrofit就是通过okhttp来进行网络请求的

Call<WeatherBeans> call = netService.requestWeatherBeans();

call.enqueue(new Callback<WeatherBeans>() {
            @Override
            public void onResponse(Call<WeatherBeans> call, Response<WeatherBeans> response) {
                if (response.isSuccessful()) {
                    WeatherBeans beans = response.body();
                    for (WeatherBeans.ResultBean bean : beans.getResult()) {
                        Log.d("cityName", bean.getCitynm());
                        Log.d("days", bean.getDays());
                    }
                }
            }

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

            }
        });

       

3、注解说明

见注解详解