布局控件使用recyclerview+cardview
本篇不涉及封裝，只是簡單的實現
先看下目錄結構

Rxjava2目錄結構.jpg

Rxjava2實現網絡請求需要的包.jpg

    <uses-permission android:name="android.permission.INTERNET" />
    <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />

先上基本代碼，寫了一個單例
RetrofitManager.class

import com.jakewharton.retrofit2.adapter.rxjava2.RxJava2CallAdapterFactory;
import retrofit2.Retrofit;
import retrofit2.converter.gson.GsonConverterFactory;

public class RetrofitManager {
    static final String BASE_URL = "http://news-at.zhihu.com/api/4/news/";
    private Retrofit retrofit;
    private static RetrofitManager ourInstance = new RetrofitManager();

    public static RetrofitManager getInstance() {
        return ourInstance;
    }

    private RetrofitManager() {
    }
    /**
     * 獲取retrofit單例
     * @return Retrofit single
     */
    public Retrofit getRetrofit() {
        if (retrofit == null) {
            retrofit = new Retrofit.Builder()
                    .baseUrl(BASE_URL)
                    .addCallAdapterFactory(RxJava2CallAdapterFactory.create())
                    .addConverterFactory(GsonConverterFactory.create())
                    .build();
        }
        return retrofit;
    }
}

實體類entity.class,這里只展示主要代碼

public class entity {
 private List<StoriesBean> stories;
    public List<StoriesBean> getStories() {
        return stories;
    }
    public void setStories(List<StoriesBean> stories) {
        this.stories = stories;
    }
 public static class StoriesBean {
        private String title;
        private List<String> images;
        public String getTitle() {
            return title;
        }
        public void setTitle(String title) {
            this.title = title;
        }
        public List<String> getImages() {
            return images;
        }
        public void setImages(List<String> images) {
            this.images = images;
        }
    }
 }

GetNews接口

import com.haoyan.myrxjava.entity.Results;
import io.reactivex.Observable;
import okhttp3.ResponseBody;
import retrofit2.http.GET;
import retrofit2.http.Url;

public interface GetNews {
    @GET("latest")
    Observable<Results> getNews();

    @GET
    Observable<ResponseBody> getPicFromNet(@Url String url);
}

主類：MainActivity.class
主要看點是map將url轉為bitmap

import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.DefaultItemAnimator;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.view.View;
import android.widget.Toast;

import com.haoyan.myrxjava.adapter.SimpleAdapters;
import com.haoyan.myrxjava.entity.entity;
import com.haoyan.myrxjava.http.GetNews;
import com.haoyan.myrxjava.http.RetrofitManager;
import com.haoyan.myrxjava.utils.MyViewHolder;

import java.util.ArrayList;
import java.util.List;

import io.reactivex.Observer;
import io.reactivex.android.schedulers.AndroidSchedulers;
import io.reactivex.annotations.NonNull;
import io.reactivex.disposables.Disposable;
import io.reactivex.functions.Consumer;
import io.reactivex.functions.Function;
import io.reactivex.schedulers.Schedulers;
import okhttp3.ResponseBody;

public class MainActivity extends AppCompatActivity {
    private RecyclerView mRecyclerView;
    private SimpleAdapters mAdapter;
    private List<entity.StoriesBean> storiesList;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        storiesList = new ArrayList<>();
        initViews();
        getDataByRetrofit();
    }

    private void initViews() {
        mRecyclerView = (RecyclerView) findViewById(R.id.main_recycler);
        mAdapter = new SimpleAdapters(this, storiesList, R.layout.item_rock) {

            @Override
            public void convert(final MyViewHolder holder, final entity.StoriesBean storiesList) {
                String url = storiesList.getImages().get(0);
                GetNews getBitmap = RetrofitManager.getInstance().getRetrofit().create(GetNews.class);
                getBitmap.getPicFromNet(url)
                        .map(new Function<ResponseBody, Bitmap>() {
                            @Override
                            public Bitmap apply(@NonNull ResponseBody responseBody) throws Exception {
                                return BitmapFactory.decodeStream(responseBody.byteStream());
                            }
                        })
                        .subscribeOn(Schedulers.io())
                        .observeOn(AndroidSchedulers.mainThread())
                        .subscribe(new Consumer<Bitmap>() {
                            @Override
                            public void accept(@NonNull Bitmap bitmap) throws Exception {
                                holder.setText(R.id.tv_title,storiesList.getTitle())
                                        .setImageBitamp(R.id.iv_img,bitmap);
                            }

                        });
            }
        };
        mRecyclerView.setAdapter(mAdapter);
        //設置recyclerview布局管理器
        LinearLayoutManager linearLayoutManager = new LinearLayoutManager(this, LinearLayoutManager.VERTICAL, false);
        mRecyclerView.setLayoutManager(linearLayoutManager);

        mRecyclerView.setItemAnimator(new DefaultItemAnimator());

        mAdapter.setOnItemClickListener(new SimpleAdapters.OnItemClickListener() {
            @Override
            public void onItemClick(View view, int position) {
                Toast.makeText(MainActivity.this, "click:" + position, Toast.LENGTH_SHORT).show();
            }

            @Override
            public void onItemLongClick(View view, int position) {
                Toast.makeText(MainActivity.this, "longclick:" + position, Toast.LENGTH_SHORT).show();
            }
        });
    }
    //get data by Retrofit & RxJava
    private void getDataByRetrofit() {
        //主要邏輯
        GetNews getNews = RetrofitManager.getInstance().getRetrofit().create(GetNews.class);
        getNews.getNews()
                .subscribeOn(Schedulers.io())
                .observeOn(AndroidSchedulers.mainThread())
                .subscribe(new Observer<entity>() {

                    @Override
                    public void onSubscribe(@NonNull Disposable d) {

                    }

                    @Override
                    public void onNext(@NonNull entity entity) {
                        storiesList.addAll(entity.getStories());
                        mAdapter.notifyDataSetChanged();
                    }

                    @Override
                    public void onError(@NonNull Throwable e) {
                        Toast.makeText(MainActivity.this, e.getMessage(), Toast.LENGTH_SHORT).show();
                    }

                    @Override
                    public void onComplete() {

                    }
                });
    }

}

Rxjava2給出學者的學習鏈接
Retrofit2 完全解析 探索與okhttp之間的關系
有些問題是1與2的問題
Rxjava1與Rxjava2比較