Question

我正在尝试从API http://api.themoviedb.org/3/movie/中通过翻新和gson检索json。我的主要活动正常，但是当我在DetailsActivity中调用其他信息时，我发现数组中的模型是空的。这很奇怪，因为我从api中甚至接收到数组中正确数量的对象。但是，当我从模型中记录一个值（例如Log.d（TAG，movieTrailers.get（0）.getName（））时，应用程序崩溃。如果执行if语句，我会发现该值为空。

例如，这是API http://api.themoviedb.org/3/movie/297802/videos?api_key=。（很遗憾，我不允许发布api键）它包含在有关电影的视频的jsonarray中。

这是我的代码：

模型：

public class MovieTrailer {

    @SerializedName("key")
    private String key;
    @SerializedName("name")
    private String name;
    @SerializedName("type")
    private String type;

    public MovieTrailer(String key, String name, String type){
        this.key = key;
        this.name = name;
        this.type = type;
    }

    public String getKey() {
        return key;
    }

    public void setKey(String key) {
        this.key = key;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getType() {
        return type;
    }

    public void setType(String type) {
        this.type = type;
    }

}

列表模型：

public class TrailersList {
    @SerializedName("results")
    @Expose
    private List<MovieTrailer> trailers = null;

    public List<MovieTrailer> getTrailers() {
        return trailers;
    }

    public void setTrailers(List<MovieTrailer> trailers) {
        this.trailers = trailers;
    }
}

适配器：

public class VideoAdapter extends RecyclerView.Adapter<VideoAdapter.VideoAdapterViewHolder> {

    private List<MovieTrailer> movieTrailers;

    private final  VideoOnClickHandler videoOnClickHandler;

    public interface VideoOnClickHandler{
        void onClick(MovieTrailer movieTrailer);
    }

    public VideoAdapter(VideoOnClickHandler onClickHandler) {videoOnClickHandler = onClickHandler;}

    public class VideoAdapterViewHolder extends RecyclerView.ViewHolder implements View.OnClickListener{

        public final TextView videoTypeText;
        public final TextView videoNameText;

        public VideoAdapterViewHolder(View view){
            super(view);
            videoTypeText = (TextView) view.findViewById(R.id.tv_video_type);
            videoNameText = (TextView) view.findViewById(R.id.tv_video_name);
            view.setOnClickListener(this);
        }

        @Override
        public void onClick(View view) {
            int adapterPosition = getAdapterPosition();
            MovieTrailer movieTrailer = movieTrailers.get(adapterPosition);
            videoOnClickHandler.onClick(movieTrailer);
        }
    }

    @NonNull
    @Override
    public VideoAdapterViewHolder onCreateViewHolder(@NonNull ViewGroup viewGroup, int i) {
        Context context = viewGroup.getContext();
        int gridItem = R.layout.movie_trailer;
        LayoutInflater inflater = LayoutInflater.from(context);
        boolean shouldAttachToParentImmediately = false;

        View view = inflater.inflate(gridItem, viewGroup,shouldAttachToParentImmediately);

        return new VideoAdapter.VideoAdapterViewHolder(view);
    }

    @Override
    public void onBindViewHolder(@NonNull VideoAdapterViewHolder videoAdapterViewHolder, int i) {
        MovieTrailer movieTrailer = movieTrailers.get(i);
        videoAdapterViewHolder.videoTypeText.setText(movieTrailer.getType());
        videoAdapterViewHolder.videoNameText.setText(movieTrailer.getName());
    }

    @Override
    public int getItemCount() {
        if (null == movieTrailers) return 0;
        return movieTrailers.size();
    }

    //Function to set movieTrailers
    public void setMovieTrailerArray(List<MovieTrailer> trailerArrayToSet){
        movieTrailers = trailerArrayToSet;
        notifyDataSetChanged();
    }


}

界面：

public interface GetDataService {

    @GET("{path}?api_key=" + BuildConfig.API_KEY)
    Call<MoviesList> getAllMovies(@Path("path") String path);

    @GET("{movieId}/reviews?api_key=" + BuildConfig.API_KEY)
    Call<TrailersList> getAllTrailers(@Path("movieId") String movieId);

    @GET("{movieId}/videos?api_key=" + BuildConfig.API_KEY)
    Call<ReviewsList> getAllReviews(@Path("movieId") String movieId);
}

改造实例：

public class RetrofitClientInstance {

    //Base URL for API request
    private static final String MOVIE_DATABASE_URL_POPULAR =
            "http://api.themoviedb.org/3/movie/";

    /**
     * Get Retrofit Instance
     */
    private static Retrofit getRetrofitInstance() {
        return new Retrofit.Builder()
                .baseUrl(MOVIE_DATABASE_URL_POPULAR)
                .addConverterFactory(GsonConverterFactory.create())
                .build();
    }

    /**
     * Get API Service
     *
     * @return API Service
     */
    public static GetDataService getApiService() {
        return getRetrofitInstance().create(GetDataService.class);
    }
}

以及DetailsActivity中的方法：

private void loadMovieTrailers(String movieId){
        GetDataService api = RetrofitClientInstance.getApiService();
        Call<TrailersList> call = api.getAllTrailers(movieId);

        call.enqueue(new Callback<TrailersList>() {
            @Override
            public void onResponse(Call<TrailersList> call, Response<TrailersList> response) {
                if(response.isSuccessful()){
                    movieTrailers = response.body().getTrailers();
                    if(movieTrailers.get(0).getName() == null){
                        Log.d("MODEL", "Null");
                    }else {
                        Log.d("MODEL", "Not Null");
                    }

                    videoAdapter.setMovieTrailerArray(movieTrailers);
                }
            }

            @Override
            public void onFailure(Call<TrailersList> call, Throwable t) {
            }
        });
    }

有人知道错误在哪里？

Answer 1

我认为问题出在这些方法的接口类中，

@GET("{movieId}/reviews?api_key=" + BuildConfig.API_KEY)
Call<TrailersList> getAllTrailers(@Path("movieId") String movieId);

@GET("{movieId}/videos?api_key=" + BuildConfig.API_KEY)
Call<ReviewsList> getAllReviews(@Path("movieId") String movieId);

从{movieId}/reviews中，您将获得以下JSON响应，

{
  "id": 297761,
  "page": 1,
  "results": [
    {
      "id": "57a814dc9251415cfb00309a",
      "author": "Frank Ochieng",
      "content": "Summertime 2016 has not been very kind to DC Comics-based personalities looking to shine consistently like their big screen Marvel Comics counterparts.",
      "url": "https://www.themoviedb.org/review/57a814dc9251415cfb00309a"
    }
  ],
  "total_pages": 1,
  "total_results": 1
}

和{movieId}/videos返回，

{
  "id": 550,
  "results": [
    {
      "id": "533ec654c3a36854480003eb",
      "iso_639_1": "en",
      "iso_3166_1": "US",
      "key": "SUXWAEX2jlg",
      "name": "Trailer 1",
      "site": "YouTube",
      "size": 720,
      "type": "Trailer"
    }
  ]
}

因此，它们都返回几乎相同的结果，并带有包含在JSONObject中的JSONArray（results）。 JSON响应是正确的，根本没有问题。

在解析JSON响应时，Gson转换器工厂无法找到该响应的等效POJO类。您甚至都不会得到任何错误，因为两者都返回相同的类型响应。

一个简单的解决方法是更改（相互更改）以下方法的URL。

@GET("{movieId}/videos?api_key=" + BuildConfig.API_KEY)   // change from reviews to videos
Call<TrailersList> getAllTrailers(@Path("movieId") String movieId);  

@GET("{movieId}/reviews?api_key=" + BuildConfig.API_KEY)   // change from videos to reviews
Call<ReviewsList> getAllReviews(@Path("movieId") String movieId);

就是这样！

Answer 2

在MovieTrailer类中，这些字段缺少@Expose批注。因此，Gson创建了对象，但没有找到任何字段来放入实际数据。

顺便说一句。仅当JSON中的字段名称与模型中的字段名称不同时，才需要@SerializedFieldName。

Answer 3

在我的情况下，我的调试apk正常工作，但是在创建发布apk时，模型的所有数据都显示为空，除非数据用Expose和SerializedName注释。尽管我的键名和变量名相同，但是我仍然必须添加SerializedName，但不确定为什么。

因此，如果您尚未添加它们，请添加这两个注释。

简而言之，将private int id;转换为此@Expose @SerializedName("id") private int id;

Retrofit / Gson将空模型放入List <>

3 个答案: