如何在对象 Gson/Retrofit2 中获取字符串

Question

我正在对这个 Google Books API URL做出回应

我有一个改造请求：'

public interface BookApiService {

    @GET("/books/v1/volumes")
    Call<Books> getBooks(@Query("q") String query);
}

并且有一个实体类

Books.java

public class Books {

    @SerializedName("items")
    @Expose
    private List<Book> items;

    public List<Book> getItems() {
        return items;
    }
}

和Book.java

public class Book {

    @SerializedName("title")
    @Expose
    private String mTitle;
    public String getTitle() {
        return mTitle;
    }
}

请求工作正常，我的意思是连接没有错误，并且改造返回 onResponse，而不是 onFailure。 但我的字符串“标题”为空。我怎么能得到这个。请通过上面的链接检查 JSON 响应。

更新：

改装电话：

public class BookService{

    private static final String BASE_URL = "https://www.googleapis.com/";
    private BookApiService mApiService;
    private BookCallback mListener;

    public BookService(BookCallback listener){
        Retrofit retrofit = new Retrofit.Builder()
                .addConverterFactory(GsonConverterFactory.create())
                .baseUrl(BASE_URL)
                .build();

        mApiService = retrofit.create(BookApiService.class);

        mListener = listener;
    }



    public void getBooks(String query){
        Call<Books> call = mApiService.getBooks(query);
        call.enqueue(new Callback<Books>() {
            @Override
            public void onResponse(Call<Books> call, Response<Books> response) {
                mListener.notifyDataReceived(response.body());
            }

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

                mListener.notifyErrorReceived(t);
            }
        });
    }

    public interface BookCallback{
        void notifyDataReceived(Books books);
        void notifyErrorReceived(Throwable error);
    }

BookCallback 监听器是我的 MainActivity： 当我检查日志时，有

"SUCCESS" "TITLE 1 null"

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    mRecyclerView = findViewById(R.id.recycler_view);
    mRecyclerView.addItemDecoration(new DividerItemDecoration(mRecyclerView.getContext(), DividerItemDecoration.VERTICAL));
    mRecyclerView.setLayoutManager(new LinearLayoutManager(this));
    new BookService(this).getBooks("android");

}

@Override
public void notifyDataReceived(Books books) {
    if(books.getItems() != null) {
        List<Book> items = books.getItems();
        Log.d(TAG, "Success");
        Log.d(TAG, "TITLE 1" + items.get(0).getTitle());
        setupAdapter(items);
    }
}

Answer 1

您可以直接在浏览器here 中请求 JSON。仔细查看此数据，您会发现items[0] 没有属性title。相反，有一个属性volumeInfo 包含title。您的 Retrofit 实体类需要正确导航到该属性才能获取您需要的数据。