public class JsonResult {
/**
     * success : true
     * code : 10000
     * message : 获取成功
     * data : [{"id":"1343753738156515328","title":"Android加载大图片，解决OOM问题","viewCount":206,"commentCount":59,"publishTime":"2020-12-29T03:00:31.570+0000","userName":"程序员拉大锯","cover":"/imgs/7.png"},{"id":"1343753738156515329","title":"Volley/Xutils对大图片处理算法源码分析","viewCount":50,"commentCount":71,"publishTime":"2020-12-29T03:00:31.570+0000","userName":"程序员拉大锯","cover":"/imgs/1.png"},{"id":"1343753738156515330","title":"Android开发网络安全配置","viewCount":68,"commentCount":105,"publishTime":"2020-12-29T03:00:31.570+0000","userName":"程序员拉大锯","cover":"/imgs/7.png"},{"id":"1343753738156515331","title":"Android开发网络编程，请求图片","viewCount":197,"commentCount":69,"publishTime":"2020-12-29T03:00:31.570+0000","userName":"程序员拉大锯","cover":"/imgs/14.png"},{"id":"1343753738156515332","title":"Intent页面跳转工具类分享","viewCount":308,"commentCount":49,"publishTime":"2020-12-29T03:00:31.570+0000","userName":"程序员拉大锯","cover":"/imgs/7.png"},{"id":"1343753738156515333","title":"阳光沙滩商城的API文档","viewCount":232,"commentCount":75,"publishTime":"2020-12-29T03:00:31.570+0000","userName":"程序员拉大锯","cover":"/imgs/15.png"},{"id":"1343753738156515334","title":"Android课程视频打包下载","viewCount":77,"commentCount":103,"publishTime":"2020-12-29T03:00:31.570+0000","userName":"程序员拉大锯","cover":"/imgs/0.png"},{"id":"1343753738156515335","title":"非常轻量级的gif录制软件","viewCount":144,"commentCount":81,"publishTime":"2020-12-29T03:00:31.570+0000","userName":"程序员拉大锯","cover":"/imgs/3.png"},{"id":"1343753738156515336","title":"Fiddler抓包工具，墙裂推荐，功能很强大很全的一个工具","viewCount":259,"commentCount":58,"publishTime":"2020-12-29T03:00:31.570+0000","userName":"程序员拉大锯","cover":"/imgs/9.png"},{"id":"1343753738156515337","title":"AndroidStudio奇淫技巧-代码管理","viewCount":325,"commentCount":66,"publishTime":"2020-12-29T03:00:31.570+0000","userName":"程序员拉大锯","cover":"/imgs/16.png"},{"id":"1343753738156515338","title":"OC和Swift混编","viewCount":310,"commentCount":88,"publishTime":"2020-12-29T03:00:31.570+0000","userName":"程序员拉大锯","cover":"/imgs/13.png"},{"id":"1343753738156515339","title":"最新的Android studio是不是没有Android Device Monitor","viewCount":214,"commentCount":17,"publishTime":"2020-12-29T03:00:31.570+0000","userName":"程序员拉大锯","cover":"/imgs/10.png"}]
     */

    private boolean success;
    private int code;
    private String message;
    private List<DataBean> data;

    public boolean isSuccess() {
        return success;
    }

    public void setSuccess(boolean success) {
        this.success = success;
    }

    public int getCode() {
        return code;
    }

    public void setCode(int code) {
        this.code = code;
    }

    public String getMessage() {
        return message;
    }

    public void setMessage(String message) {
        this.message = message;
    }

    public List<DataBean> getData() {
        return data;
    }

    public void setData(List<DataBean> data) {
        this.data = data;
    }

    public static class DataBean {
        /**
         * id : 1343753738156515328
         * title : Android加载大图片，解决OOM问题
         * viewCount : 206
         * commentCount : 59
         * publishTime : 2020-12-29T03:00:31.570+0000
         * userName : 程序员拉大锯
         * cover : /imgs/7.png
         */

        private String id;
        private String title;
        private int viewCount;
        private int commentCount;
        private String publishTime;
        private String userName;
        private String cover;

        public String getId() {
            return id;
        }

        public void setId(String id) {
            this.id = id;
        }

        public String getTitle() {
            return title;
        }

        public void setTitle(String title) {
            this.title = title;
        }

        public int getViewCount() {
            return viewCount;
        }

        public void setViewCount(int viewCount) {
            this.viewCount = viewCount;
        }

        public int getCommentCount() {
            return commentCount;
        }

        public void setCommentCount(int commentCount) {
            this.commentCount = commentCount;
        }

        public String getPublishTime() {
            return publishTime;
        }

        public void setPublishTime(String publishTime) {
            this.publishTime = publishTime;
        }

        public String getUserName() {
            return userName;
        }

        public void setUserName(String userName) {
            this.userName = userName;
        }

        public String getCover() {
            return cover;
        }

        public void setCover(String cover) {
            this.cover = cover;
        }
    }
}


以下是RecycleView适配器的代码：

public class JsonResultAdapter extends RecyclerView.Adapter<JsonResultAdapter.InnerHolder> {
    private static final String TAG = "JsonResultAdapter";
    private List<JsonResult.DataBean> data = new ArrayList<>();

    @NonNull
    @Override
    public InnerHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
        View itemView = LayoutInflater.from(parent.getContext()).inflate(R.layout.item_json_result, parent, false);
        return new InnerHolder(itemView);
    }

    @Override
    public void onBindViewHolder(@NonNull InnerHolder holder, int position) {
        //绑定数据
        ImageView coverView = holder.itemView.findViewById(R.id.result_cover);
        TextView titleTv = holder.itemView.findViewById(R.id.result_title);
        TextView authorTv= holder.itemView.findViewById(R.id.result_author);
        JsonResult.DataBean dataBean = data.get(position);
        titleTv.setText(dataBean.getTitle());
        authorTv.setText(dataBean.getUserName());
     //   Picasso.get().load();
        Log.d(TAG,"cover url --->" +dataBean.getCover());

    }

    @Override
    public int getItemCount() {
        return data.size();
    }

    public void setData(JsonResult jsonResult) {
      data.clear();
      data.addAll(jsonResult.getData());
      notifyDataSetChanged();
    }

    public  class InnerHolder extends RecyclerView.ViewHolder {
        public InnerHolder(@NonNull View itemView) {
            super(itemView);
        }
    }
}

MainActivity中的代码：

public class MainActivity extends AppCompatActivity {

    private static final String TAG = "MainActivity";
    private RecyclerView mResultList;
    private JsonResultAdapter mAdapter;

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

    private void initView() {
        mResultList = findViewById(R.id.result_list);
        mResultList.setLayoutManager(new LinearLayoutManager(this));
        mAdapter = new JsonResultAdapter();
        mResultList.setAdapter(mAdapter);
        mResultList.addItemDecoration(new RecyclerView.ItemDecoration() {
            @Override
            public void getItemOffsets(@NonNull Rect outRect, @NonNull View view, @NonNull RecyclerView parent, @NonNull RecyclerView.State state) {
                outRect.top=5;
                outRect.bottom=5;
            }
        });
    }

    public void  getRequest(View view){
        Retrofit retrofit = new Retrofit.Builder()
                .baseUrl("http://10.0.2.2:9102")
                .build();
        API api = retrofit.create(API.class);
        Call<ResponseBody> task = api.getJson();
        task.enqueue(new Callback<ResponseBody>() {
            @Override
            public void onResponse(Call<ResponseBody> call, Response<ResponseBody> response) {
                Log.d(TAG,"onResponse--->"+response.code());
                if (response.code()== HttpURLConnection.HTTP_OK){
                    try {
                        Log.d(TAG,"json--->"+response.body().string());
                    String result =response.body().string();
                    Gson gson =new Gson();
                    //把字符串转换成对象
                        JsonResult jsonResult = gson.fromJson(result, JsonResult.class);
                        updateList(jsonResult);



                    } catch (IOException e) {
                        e.printStackTrace();
                    }
                }
            }

            @Override
            public void onFailure(Call<ResponseBody> call, Throwable t) {
        Log.d(TAG,"onFailure..."+ t.toString());
            }
        });

    }

    private void updateList(JsonResult jsonResult) {
        mAdapter.setData(jsonResult);
    }
}

以下是Log
2020-12-29 12:08:09.060 6683-6683/com.example.retorfitdemo E/AndroidRuntime: FATAL EXCEPTION: main
    Process: com.example.retorfitdemo, PID: 6683
    java.lang.NullPointerException: Attempt to invoke virtual method 'java.util.List com.example.retorfitdemo.domain.JsonResult.getData()' on a null object reference
        at com.example.retorfitdemo.adapter.JsonResultAdapter.setData(JsonResultAdapter.java:55)
        at com.example.retorfitdemo.MainActivity.updateList(MainActivity.java:89)
        at com.example.retorfitdemo.MainActivity.access$000(MainActivity.java:26)
        at com.example.retorfitdemo.MainActivity$2.onResponse(MainActivity.java:70)
        at retrofit2.DefaultCallAdapterFactory$ExecutorCallbackCall$1.lambda$onResponse$0$DefaultCallAdapterFactory$ExecutorCallbackCall$1(DefaultCallAdapterFactory.java:81)
        at retrofit2.-$$Lambda$DefaultCallAdapterFactory$ExecutorCallbackCall$1$3wC8FyV4pyjrzrYL5U0mlYiviZw.run(Unknown Source:6)
        at android.os.Handler.handleCallback(Handler.java:938)
        at android.os.Handler.dispatchMessage(Handler.java:99)
        at android.os.Looper.loop(Looper.java:223)
        at android.app.ActivityThread.main(ActivityThread.java:7656)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:592)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:947)
2020-12-29 12:08:09.135 6683-6683/? I/Process: Sending signal. PID: 6683 SIG: 9