activity.java

package com.example.hanlufeng.retrofitdemo;


import android.app.Activity;
import android.os.Bundle;
import android.util.Log;

import com.google.gson.Gson;
import com.google.gson.GsonBuilder;

import java.io.IOException;
import java.lang.annotation.Annotation;
import java.lang.reflect.Type;
import java.util.concurrent.TimeUnit;

import okhttp3.MediaType;
import okhttp3.OkHttpClient;
import okhttp3.RequestBody;
import okhttp3.ResponseBody;
import okhttp3.logging.HttpLoggingInterceptor;
import retrofit2.Converter;
import retrofit2.Retrofit;
import retrofit2.adapter.rxjava.RxJavaCallAdapterFactory;
import retrofit2.converter.gson.GsonConverterFactory;
import rx.Observable;
import rx.android.schedulers.AndroidSchedulers;
import rx.functions.Action1;
import rx.functions.Func0;
import rx.functions.Func1;
import rx.schedulers.Schedulers;

public class MainActivity extends Activity {

    OkHttpClient client;
    Retrofit retrofit;
    ApiEndpoints apiService;
    final String url = "http://javascript.info/tutorial/hello-world";

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        HttpLoggingInterceptor logging = new HttpLoggingInterceptor();
        logging.setLevel(HttpLoggingInterceptor.Level.BODY);

        this.client = new OkHttpClient.Builder()
                .addInterceptor(logging)
                .connectTimeout(25, TimeUnit.SECONDS)
                .readTimeout(25, TimeUnit.SECONDS)
                .build();

        // retrofit with custom client
        this.retrofit = new Retrofit.Builder()
                .baseUrl("https://api.github.com/")
                .addConverterFactory(new ToStringConverterFactory())
                .addCallAdapterFactory(RxJavaCallAdapterFactory.create())
                .client(client)
                .build();
        this.apiService = retrofit.create(ApiEndpoints.class);

        Observable<String> responseBodyObservable = apiService.rxGetImageCall(url).subscribeOn(Schedulers.io());

        responseBodyObservable.observeOn(AndroidSchedulers.mainThread())
                .subscribe(new Action1<String>() {
                    @Override
                    public void call(String s) {
                        Log.i("TEST", "--------------------------------");
                        Log.i("RESULT", s);
                    }
                }, new Action1<Throwable>() {
                    @Override
                    public void call(Throwable throwable) {
                        Log.i("TEST", "--------------------------------");
                        Log.i("ERROR", throwable.toString());
                    }
                });
    }


}

interface.java

package com.example.hanlufeng.retrofitdemo;

import retrofit2.http.GET;
import retrofit2.http.Url;
import rx.Observable;

interface ApiEndpoints {
    @GET
    Observable<String> rxGetImageCall(@Url String imageUrl);
}

ToStringConverterFactory.java

//## from https://github.com/kamilwlf/Kamil-thoughts/blob/master/ToStringConverterFactory.java

package com.example.hanlufeng.retrofitdemo;

import java.io.IOException;
import java.lang.annotation.Annotation;
import java.lang.reflect.Type;

import okhttp3.ResponseBody;
import retrofit2.Converter;
import retrofit2.Retrofit;

class ToStringConverterFactory extends Converter.Factory {
    @Override
    public Converter<ResponseBody, ?> responseBodyConverter(Type type, Annotation[] annotations, Retrofit retrofit) {
        if (String.class.equals(type)) {
            return new Converter<ResponseBody, String>() {
                @Override
                public String convert(ResponseBody value) throws IOException {
                    return value.string();
                }
            };
        }
        return null;
    }
}