Android 如何解析这个json的；标题“&引用；作者&&引用；“小缩略图”；并使用GSON转换器检查json密钥是否存在

如何仅在GSON的帮助下解析“标题”、“作者”和“小缩略图”。注意：如果找不到作者和smallThunbnail，则输出应为NULL/notfound。如何在RecyclerViewIn（onBindViewHolder）方法中实现代码。我正在对网络部分进行改造。我已经把代码放在下面了。请帮助我，我是Android开发的新手。先谢谢你

{
  "kind": "books#volumes",
  "items": [
    {
      "id": "t4rgAAACAZAJ",   
      "volumeInfo": {
        "title": "Harry Review",
        "authors": [
          "International ISBN Agency"
        ],
               
        "imageLinks": {
          "smallThumbnail": "http://books.google.com/books/content?id=t5rgAAAAMAAJ&printsec=frontcover&img=1&zoom=5&source=gbs_api",
          
        }
              
      }
    },
    
    {
      "id": "t5rgAAAAMAAJ",  
      "volumeInfo": {
        "title": "ISBN Review",
        "authors": [
          
        ],
               
        "imageLinks": {
          
        }
              
      }
    }
  ]
}

如何在下面的代码中实现它

图书班

    package com.example.retrofitbook;

import java.util.List;

public class Book {
    private String title;
    private List<Author> authors;
    Imagelink imageLinks;

    public Book(String title, List<Author> authors, Imagelink imageLinks) {
        this.title = title;
        this.authors = authors;
        this.imageLinks = imageLinks;
    }

    public String getTitle() {
        return title;
    }

    public List<Author> getAuthors() {
        return authors;
    }

    public Imagelink getImageLinks() {
        return imageLinks;
    }
}

Imagelink类

  public class Imagelink  {

    private String smallThumbnail;

    public Imagelink(String smallThumbnail) {
        this.smallThumbnail = smallThumbnail;
    }

    public String getSmallThumbnail() {
        return smallThumbnail;
    }
}

循环水泵

public class RecyclerViewAdapter  extends RecyclerView.Adapter<RecyclerViewAdapter.MyViewHolder> {


    private Context mContext;
    private List<Book> mData;

    public RecyclerViewAdapter(Context mContext, List<Book> mData) {
        this.mContext = mContext;
        this.mData = mData;
    }
    @NonNull
    @Override
    public MyViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
        View view;
        LayoutInflater inflater = LayoutInflater.from(mContext);
        view = inflater.inflate(R.layout.book_raw , parent , false);
        final MyViewHolder viewHolder =  new MyViewHolder(view);

        return viewHolder;
    }

    @Override
    public void onBindViewHolder(@NonNull MyViewHolder holder, int i) {
        Book book = mData.get(i);     
        holder.tvTitle.setText(book.getTitle());

        Glide.with(mContext).load(book.getImageLinks().getSmallThumbnail()).into(holder.ivThumbnail);


    }

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

    public static class MyViewHolder extends RecyclerView.ViewHolder {

        ImageView ivThumbnail ;
        TextView tvTitle , tvAuthor;
        LinearLayout container ;

        public MyViewHolder(@NonNull View itemView) {
            super(itemView);

            ivThumbnail = itemView.findViewById(R.id.cover_image);
            tvTitle = itemView.findViewById(R.id.book_title);
            tvAuthor =  itemView.findViewById(R.id.author);
            container = itemView.findViewById(R.id.container);

        }
    }
}

公共类RecycleServiceAdapter扩展了RecyclerView.Adapter{
私有上下文；
私有列表数据；
公共RecycleServiceAdapter（上下文mContext，列表mData）{
this.mContext=mContext；
this.mData=mData；
}
@非空
@凌驾
public MyViewHolder onCreateViewHolder（@NonNull ViewGroup父级，int-viewType）{
视图；
LayoutFlater充气机=LayoutFlater.from（mContext）；
视图=充气机。充气（R.layout.book\u原始、父级、假）；
最终MyViewHolder viewHolder=新MyViewHolder（视图）；
返回视图持有者；
}
@凌驾
public void onBindViewHolder（@NonNull MyViewHolder，int i）{
Book Book=mData.get（i）；
holder.tvTitle.setText（book.getTitle（））；
Glide.with（mContext）.load（book.getImageLinks（）.getSmallThumbnail（））到（holder.ivThumbnail）中；
}
@凌驾
public int getItemCount（）{
返回mData.size（）；
}
公共静态类MyViewHolder扩展了RecyclerView.ViewHolder{
图像视图；
TextView tvTitle，tvAuthor；
线性布局集装箱；
公共MyViewHolder（@NonNull View itemView）{
超级（项目视图）；
ivThumbnail=itemView.findViewById（R.id.cover\u图像）；
tvTitle=itemView.findviewbyd（R.id.book\u title）；
tvAuthor=itemView.findViewById（R.id.author）；
container=itemView.findviewbyd（R.id.container）；
}
}
}

MyWebService

  public interface MyWebService {

    String BASE_URL = "https://www.googleapis.com/books/";

    Retrofit retrofit = new Retrofit.Builder().baseUrl(BASE_URL)
            .addConverterFactory(GsonConverterFactory.create())
            .build();

    @GET("v1/volumes")
    Call<List<Book>> getApi (@Query("q") String str);

}

公共接口MyWebService{
字符串BASE_URL=”https://www.googleapis.com/books/";
改装改装=新改装.Builder（）.baseUrl（基本URL）
.addConverterFactory（GsonConverterFactory.create（））
.build（）；
@获取（“v1/卷”）
调用getApi（@Query（“q”）String str）；
}

主要活动

 public class MainActivity extends AppCompatActivity {

    MyWebService nWebService;
    private String text;
     ArrayList<Book> mBooks= new ArrayList<>();
    private RecyclerView mRecycleView;
    private RecyclerViewAdapter mAdapter;
    TextView emptyView;
    ProgressBar loadingIndicator;


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

        //Find the reference to the progressbar
        loadingIndicator = findViewById(R.id.loading_progress);
        emptyView = findViewById(R.id.empty_view);

        mRecycleView= findViewById(R.id.recycler_list);
        mRecycleView.setHasFixedSize(true);
        LinearLayoutManager manager = new LinearLayoutManager(this);
        mRecycleView.setLayoutManager(manager);


        nWebService = MyWebService.retrofit.create(MyWebService.class);
        loadJson();


    }

    private void loadJson() {
        Call<List<Book>> call = nWebService.getApi();
        call.enqueue(new Callback<List<Book>>() {
            @Override
            public void onResponse(Call<List<Book>> call, Response<List<Book>> response) {
                mBooks= new ArrayList<>(response.body());
                mAdapter = new RecyclerViewAdapter(MainActivity.this, mBooks);
                mRecycleView.setAdapter(mAdapter);


                Toast.makeText(getApplicationContext(), "SUCCESS", Toast.LENGTH_SHORT).show();
            }

            @Override
            public void onFailure(Call<List<Book>> call, Throwable t) {
                Toast.makeText(getApplicationContext(), "Failure", Toast.LENGTH_SHORT).show();
            }
        });
    }
}

public类MainActivity扩展了AppCompatActivity{
MyWebService-nWebService；
私有字符串文本；
ArrayList mBooks=新的ArrayList（）；
私人回收视图mRecycleView；
私人回收设施；
文本视图清空视图；
进度条加载指示器；
@凌驾
创建时受保护的void（Bundle savedInstanceState）{
super.onCreate（savedInstanceState）；
setContentView（R.layout.activity_main）；
//查找对progressbar的引用
loadingIndicator=findViewById（R.id.加载进度）；
emptyView=findViewById（R.id.empty\u视图）；
mRecycleView=findviewbyd（R.id.recycler\u列表）；
mRecycleView.setHasFixedSize（true）；
LinearLayoutManager=新的LinearLayoutManager（此）；
mRecycleView.setLayoutManager（管理器）；
nWebService=MyWebService.Reformation.create（MyWebService.class）；
loadJson（）；
}
私有void loadJson（）{
Call Call=nWebService.getApi（）；
call.enqueue（新回调（）{
@凌驾
公共void onResponse（调用、响应）{
mBooks=newArrayList（response.body（））；
mAdapter=新的回收服务适配器（MainActivity.this，mBooks）；
mRecycleView.setAdapter（mAdapter）；
Toast.makeText（getApplicationContext（），“SUCCESS”，Toast.LENGTH\u SHORT.show（）；
}
@凌驾
失败时公共无效（调用调用，可丢弃的t）{
Toast.makeText（getApplicationContext（），“Failure”，Toast.LENGTH_SHORT.show（）；
}
});
}
}

 public class MainActivity extends AppCompatActivity {

    MyWebService nWebService;
    private String text;
     ArrayList<Book> mBooks= new ArrayList<>();
    private RecyclerView mRecycleView;
    private RecyclerViewAdapter mAdapter;
    TextView emptyView;
    ProgressBar loadingIndicator;


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

        //Find the reference to the progressbar
        loadingIndicator = findViewById(R.id.loading_progress);
        emptyView = findViewById(R.id.empty_view);

        mRecycleView= findViewById(R.id.recycler_list);
        mRecycleView.setHasFixedSize(true);
        LinearLayoutManager manager = new LinearLayoutManager(this);
        mRecycleView.setLayoutManager(manager);


        nWebService = MyWebService.retrofit.create(MyWebService.class);
        loadJson();


    }

    private void loadJson() {
        Call<List<Book>> call = nWebService.getApi();
        call.enqueue(new Callback<List<Book>>() {
            @Override
            public void onResponse(Call<List<Book>> call, Response<List<Book>> response) {
                mBooks= new ArrayList<>(response.body());
                mAdapter = new RecyclerViewAdapter(MainActivity.this, mBooks);
                mRecycleView.setAdapter(mAdapter);


                Toast.makeText(getApplicationContext(), "SUCCESS", Toast.LENGTH_SHORT).show();
            }

            @Override
            public void onFailure(Call<List<Book>> call, Throwable t) {
                Toast.makeText(getApplicationContext(), "Failure", Toast.LENGTH_SHORT).show();
            }
        });
    }
}