如何解析 json 对象内的 json 数组 retrofit2 mvvm

Question

我有一个 json 在那个对象里面有一个对象我有 json 数组我制作了 pojo 但是就像 mvvm 我不知道如何解析它并在 recyclerView 中显示它（片段）请检查我的代码，谢谢这是我的 json

{ 
"response":{ 
  "status":"ok",
  "userTier":"developer",
  "total":2157516,
  "startIndex":1,
  "pageSize":10,
  "currentPage":1,
  "pages":215752,
  "orderBy":"newest",
  "results":[ 
     { 
        "id":"uk-news/2019/dec/02/killer-of-three-elderly-devon-men-found-not-guilty-due-to-insanity",
        "type":"article",
        "sectionId":"uk-news",
        "sectionName":"UK news",
        "webPublicationDate":"2019-12-02T17:53:26Z",
        "webTitle":"Killer of three elderly Devon men found not guilty due to insanity",
        "webUrl":"https://www.theguardian.com/uk-news/2019/dec/02/killer-of-three-elderly-devon-men-found-not-guilty-due-to-insanity",
        "apiUrl":"https://content.guardianapis.com/uk-news/2019/dec/02/killer-of-three-elderly-devon-men-found-not-guilty-due-to-insanity",
        "isHosted":false,
        "pillarId":"pillar/news",
        "pillarName":"News"
     },
     { 
        "id":"football/2019/dec/02/fa-homophobic-chants-west-ham-chelsea-kick-it-out",
        "type":"article",
        "sectionId":"football",
        "sectionName":"Football",
        "webPublicationDate":"2019-12-02T17:53:09Z",
        "webTitle":"FA in discussions after homophobic chants by West Hams fans",
        "webUrl":"https://www.theguardian.com/football/2019/dec/02/fa-homophobic-chants-west-ham-chelsea-kick-it-out",
        "apiUrl":"https://content.guardianapis.com/football/2019/dec/02/fa-homophobic-chants-west-ham-chelsea-kick-it-out",
        "isHosted":false,
        "pillarId":"pillar/sport",
        "pillarName":"Sport"
     },
     { 
        "id":"news/shortcuts/2019/dec/02/jeremy-corbyn-suit-fabric-labour-leader-for-the-many-not-the-few-pinstripes",
        "type":"article",
        "sectionId":"politics",
        "sectionName":"Politics",
        "webPublicationDate":"2019-12-02T17:42:03Z",
        "webTitle":"Socialist pinstripe: the secret message stitched into Jeremy Corbyn’s new suit",
        "webUrl":"https://www.theguardian.com/news/shortcuts/2019/dec/02/jeremy-corbyn-suit-fabric-labour-leader-for-the-many-not-the-few-pinstripes",
        "apiUrl":"https://content.guardianapis.com/news/shortcuts/2019/dec/02/jeremy-corbyn-suit-fabric-labour-leader-for-the-many-not-the-few-pinstripes",
        "isHosted":false,
        "pillarId":"pillar/news",
        "pillarName":"News"
     },
     { 
        "id":"uk-news/2019/dec/02/police-criticised-response-attack-rabbi-in-north-london",
        "type":"article",
        "sectionId":"uk-news",
        "sectionName":"UK news",
        "webPublicationDate":"2019-12-02T17:41:13Z",
        "webTitle":"Police criticised over response to attack on rabbi in north London",
        "webUrl":"https://www.theguardian.com/uk-news/2019/dec/02/police-criticised-response-attack-rabbi-in-north-london",
        "apiUrl":"https://content.guardianapis.com/uk-news/2019/dec/02/police-criticised-response-attack-rabbi-in-north-london",
        "isHosted":false,
        "pillarId":"pillar/news",
        "pillarName":"News"
     },
     { 
        "id":"artanddesign/2019/dec/02/les-tasses-war-and-pissoirs-how-the-debauched-urinals-of-paris-helped-to-beat-the-nazis",
        "type":"article",
        "sectionId":"artanddesign",
        "sectionName":"Art and design",
        "webPublicationDate":"2019-12-02T17:36:28Z",
        "webTitle":"War and pissoirs: how the urinals of Paris helped beat the Nazis",
        "webUrl":"https://www.theguardian.com/artanddesign/2019/dec/02/les-tasses-war-and-pissoirs-how-the-debauched-urinals-of-paris-helped-to-beat-the-nazis",
        "apiUrl":"https://content.guardianapis.com/artanddesign/2019/dec/02/les-tasses-war-and-pissoirs-how-the-debauched-urinals-of-paris-helped-to-beat-the-nazis",
        "isHosted":false,
        "pillarId":"pillar/arts",
        "pillarName":"Arts"
     },
     { 
        "id":"commentisfree/2019/dec/02/trust-in-politics-has-evaporated-now-it-offers-only-fantasy",
        "type":"article",
        "sectionId":"commentisfree",
        "sectionName":"Opinion",
        "webPublicationDate":"2019-12-02T17:36:01Z",
        "webTitle":"Trust in politics has evaporated, now it offers only fantasy | Suzanne Moore",
        "webUrl":"https://www.theguardian.com/commentisfree/2019/dec/02/trust-in-politics-has-evaporated-now-it-offers-only-fantasy",
        "apiUrl":"https://content.guardianapis.com/commentisfree/2019/dec/02/trust-in-politics-has-evaporated-now-it-offers-only-fantasy",
        "isHosted":false,
        "pillarId":"pillar/opinion",
        "pillarName":"Opinion"
     },
     { 
        "id":"film/2019/dec/02/2019-braddies-peter-bradshaw-films-of-the-year",
        "type":"article",
        "sectionId":"film",
        "sectionName":"Film",
        "webPublicationDate":"2019-12-02T17:29:48Z",
        "webTitle":"And the 2019 Braddies go to … Peter Bradshaw's film picks of the year",
        "webUrl":"https://www.theguardian.com/film/2019/dec/02/2019-braddies-peter-bradshaw-films-of-the-year",
        "apiUrl":"https://content.guardianapis.com/film/2019/dec/02/2019-braddies-peter-bradshaw-films-of-the-year",
        "isHosted":false,
        "pillarId":"pillar/arts",
        "pillarName":"Arts"
     },
     { 
        "id":"world/2019/dec/02/christine-lagarde-ecb-should-do-more-to-tackle-climate-emergency",
        "type":"article",
        "sectionId":"world",
        "sectionName":"World news",
        "webPublicationDate":"2019-12-02T17:23:28Z",
        "webTitle":"Lagarde: ECB should do more to tackle climate emergency",
        "webUrl":"https://www.theguardian.com/world/2019/dec/02/christine-lagarde-ecb-should-do-more-to-tackle-climate-emergency",
        "apiUrl":"https://content.guardianapis.com/world/2019/dec/02/christine-lagarde-ecb-should-do-more-to-tackle-climate-emergency",
        "isHosted":false,
        "pillarId":"pillar/news",
        "pillarName":"News"
     },
     { 
        "id":"food/2019/dec/02/robert-neame-obituary",
        "type":"article",
        "sectionId":"food",
        "sectionName":"Food",
        "webPublicationDate":"2019-12-02T17:19:32Z",
        "webTitle":"Robert Neame obituary",
        "webUrl":"https://www.theguardian.com/food/2019/dec/02/robert-neame-obituary",
        "apiUrl":"https://content.guardianapis.com/food/2019/dec/02/robert-neame-obituary",
        "isHosted":false,
        "pillarId":"pillar/lifestyle",
        "pillarName":"Lifestyle"
     },
     { 
        "id":"politics/live/2019/dec/02/general-election-swinson-condemns-johnson-over-trump-friendship-ahead-of-london-visit-live",
        "type":"liveblog",
        "sectionId":"politics",
        "sectionName":"Politics",
        "webPublicationDate":"2019-12-02T17:13:40Z",
        "webTitle":"General election: Johnson insists he opposed early release for terrorists long before London Bridge attack – live news",
        "webUrl":"https://www.theguardian.com/politics/live/2019/dec/02/general-election-swinson-condemns-johnson-over-trump-friendship-ahead-of-london-visit-live",
        "apiUrl":"https://content.guardianapis.com/politics/live/2019/dec/02/general-election-swinson-condemns-johnson-over-trump-friendship-ahead-of-london-visit-live",
        "isHosted":false,
        "pillarId":"pillar/news",
        "pillarName":"News"
     }
  ]
  }
  }

现在这是我的 pojo classes.

public class NewsResponse {

@SerializedName("response")
private NewsArticle response;

public NewsArticle getResponse() {
    return response;
}

public void setResponse(NewsArticle response) {
    this.response = response;
}

 }

public class NewsArticle {

@SerializedName("results")
private List<Result> results = null;

public List<Result> getResults() {
    return results;
}

public void setResults(List<Result> results) {
    this.results = results;
}
 }

public class Result {


    @SerializedName("sectionName")
    private String sectionName;
    @SerializedName("webTitle")
    private String webTitle;
    @SerializedName("webUrl")
    private String webUrl;

public String getSectionName() {
    return sectionName;
}

public void setSectionName(String sectionName) {
    this.sectionName = sectionName;
}

public String getWebTitle() {
    return webTitle;
}

public void setWebTitle(String webTitle) {
    this.webTitle = webTitle;
}

public String getWebUrl() {
    return webUrl;
}

public void setWebUrl(String webUrl) {
    this.webUrl = webUrl;
   }
   }

这是我的新存储库

public class NewsRepository {

private static NewsRepository newsRepository;

public static NewsRepository getInstance(){
    if (newsRepository == null){
        newsRepository = new NewsRepository();
    }
    return newsRepository;
}

private NewsApi newsApi;

public NewsRepository(){
    newsApi = RetrofitService.cteateService(NewsApi.class);
}

public MutableLiveData<NewsResponse> getNews(String key){
   final MutableLiveData<NewsResponse> newsData = new MutableLiveData<>();
    newsApi.getNewsList( key).enqueue(new Callback<NewsResponse>() {
        @Override
        public void onResponse(Call<NewsResponse> call,
                               Response<NewsResponse> response) {
            if (response.isSuccessful()){
                newsData.setValue(response.body());
            }
        }

        @Override
        public void onFailure(Call<NewsResponse> call, Throwable t) {
            newsData.setValue(null);
        }
    });
    return newsData;
}
    }

现在片段

ublic class NewsFragment extends Fragment {


ArrayList<NewsResponse> articleArrayList = new ArrayList<>();
NewsAdapter newsAdapter;
RecyclerView rvHeadline;

private static final String TAG = "NewsFragment";

private PageViewModel pageViewModel;

public NewsFragment() {
    // Required empty public constructor
}

/**
 * @return A new instance of fragment SpeedDialFragment.
 */
public static NewsFragment newInstance() {
    return new NewsFragment();
}

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    pageViewModel = ViewModelProviders.of(this).get(PageViewModel.class);
}

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {
    // Inflate the layout for this fragment
    View root = inflater.inflate(R.layout.news_fragment, container, false);
    rvHeadline = root.findViewById(R.id.rvNews);


    pageViewModel.init();
    pageViewModel.getNewsRepository().observe(this, new Observer<NewsResponse>() {
        @Override
        public void onChanged(NewsResponse newsResponse) {
     ** ******      List<NewsArticle> newsArticles = newsResponse.getResponse(); ******
        *******    articleArrayList.addAll(newsArticles);   ********
            newsAdapter.notifyDataSetChanged();
        }
    });

    setupRecyclerView();
    return root;
}
private void setupRecyclerView() {
    if (newsAdapter == null) {
        newsAdapter = new NewsAdapter(getActivity(), articleArrayList);
        rvHeadline.setLayoutManager(new LinearLayoutManager(getActivity()));
        rvHeadline.setAdapter(newsAdapter);
        rvHeadline.setItemAnimator(new DefaultItemAnimator());
        rvHeadline.setNestedScrollingEnabled(true);
    } else {
        newsAdapter.notifyDataSetChanged();
    }
}
   }

我的错误在里面 pageViewModel.getNewsRepository() 我不知道该怎么办如果我将泛型更改为结果 class 第一行中修复的错误但第二行无法接受结果中的列表我迷路了请帮助

视图模型class

public class PageViewModel extends ViewModel {

private MutableLiveData<NewsResponse> mutableLiveData;
private NewsRepository newsRepository;

public void init(){
    if (mutableLiveData != null){
        return;
    }
    newsRepository = NewsRepository.getInstance();
    mutableLiveData = newsRepository.getNews( "***************");

}

public LiveData<NewsResponse> getNewsRepository() {
    return mutableLiveData;
}

  }

Answer 1

直接将 NewsRepository 的 MutableLiveData 传递给您的 ViewModel 查看。

public class PageViewModel extends ViewModel {
    private NewsRepository newsRepository = NewsRepository.getInstance();

    public MutableLiveData<NewsResponse> getNewsRepository() {
        return newsRepository.getNews( "***************");
    }
}

目前您 observe ViewModel 的 MutableLiveData 没有发出任何值。 NewsRepository 的 MutableLiveData 发出的数据在 ViewModel 中丢失，因为它没有被观察到。您必须维护 LiveData 的单个实例以观察更改。

除此之外，您必须更新片段和适配器以使用列表而不是列表，因为您的 json 不包含文章列表。它包含结果列表。检查下面

public class NewsFragment extends Fragment {


    ArrayList<Result> ArrayList = new ArrayList<>();

    ....


    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        ....

        pageViewModel.getNewsRepository().observe(this, new Observer<NewsResponse>() {
            @Override
            public void onChanged(NewsResponse newsResponse) {
                articleArrayList = newsResponse.getResponse().getResults();
                newsAdapter.notifyDataSetChanged();
            }
        });

        ....

    }

    private void setupRecyclerView() {
        if (newsAdapter == null) {
            newsAdapter = new NewsAdapter(getActivity(), resultArrayList);
            rvHeadline.setLayoutManager(new LinearLayoutManager(getActivity()));
            rvHeadline.setAdapter(newsAdapter);
            rvHeadline.setItemAnimator(new DefaultItemAnimator());
            rvHeadline.setNestedScrollingEnabled(true);
        } else {
            newsAdapter.notifyDataSetChanged();
        }
    }

}

Answer 2

编辑

我将列表更改为结果

    ArrayList<Result> articleArrayList = new ArrayList<>();

另外我在这里改了

 @Override
        public void onChanged(NewsResponse newsResponse) {
            List<Result> newsArticles = newsResponse.getResponse().getResults();
            articleArrayList.addAll(newsArticles);

并且 Md.Asaduzzaman 说我也更改了适配器并且一切正常

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