Recyclerview与OkHttp请求同步

Question

我正在尝试从 LastFm API 获取一些数据，对其进行处理，然后将其显示在回收站视图中。我的问题是，由于我的代码的结构方式，我认为我在获取数据之前初始化了我的回收器视图，所以在我重新打开我的片段之前没有显示任何东西，我不知道如何解决这个问题。

这是我的片段代码：

public class TopArtistsFragment extends Fragment {

    private RecyclerView recyclerView;
    private ArtistRecyclerViewAdapter adapter;
    private TopArtistsViewModel mArtistsViewModel;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        mArtistsViewModel = new ViewModelProvider(this).get(TopArtistsViewModel.class);

        mArtistsViewModel.init();

        mArtistsViewModel.getArtists().observe(this, new Observer<ArrayList<ArtistData>>() {
            @Override
            public void onChanged(ArrayList<ArtistData> artistData) {
                adapter.notifyDataSetChanged();
            }
        });
    }

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

       View view = inflater.inflate(R.layout.fragment_top_artists, container, false);
       recyclerView = view.findViewById(R.id.artistRecyclerView);

       return view;
    }

    @Override
    public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState) {
        super.onViewCreated(view, savedInstanceState);

        initRecyclerView();
    }

    private void initRecyclerView() {
        adapter = new ArtistRecyclerViewAdapter(mArtistsViewModel.getArtists().getValue(), getActivity());
        recyclerView.setLayoutManager(new LinearLayoutManager(getActivity(), LinearLayoutManager.VERTICAL, false));
        recyclerView.setAdapter(adapter);
    }
}

这是我的视图模型：

public class TopArtistsViewModel extends ViewModel {

    private MutableLiveData<ArrayList<ArtistData>> mArtists;
    private ArtistDataRepository mRepo;

    public void init() {
        if(mArtists != null)
                return;
        mRepo = ArtistDataRepository.getInstance();
        mArtists = mRepo.getArtists();
    }

    public LiveData<ArrayList<ArtistData>> getArtists() {
        return mArtists;
    }
}

这是我正在完成工作的存储库：

public class ArtistDataRepository {
    private static ArtistDataRepository instance;
    private ArrayList<ArtistData> dataSet = new ArrayList<>();

    public static ArtistDataRepository getInstance() {
        if(instance == null)
            instance = new ArtistDataRepository();
        return instance;
    }

    public MutableLiveData<ArrayList<ArtistData>> getArtists() {
        setArtists();

        MutableLiveData<ArrayList<ArtistData>> data = new MutableLiveData<>();
        data.setValue(dataSet);
        return data;
    }

    private void setArtists () {
        fetchData();
    }

    private void fetchData () {
        final String requestUrl = "https://ws.audioscrobbler.com/2.0/?method=chart.gettopartists&api_key=2124b8e156db20ac7a5035fad9c01b8e&format=json";

        final OkHttpClient client = new OkHttpClient();
        Request request = new Request.Builder().url(requestUrl).build();
        Call call = client.newCall(request);
        call.enqueue(new Callback() {
            @Override
            public void onFailure(@NotNull Call call, @NotNull IOException e) {
                Log.d("NETWORK FAILURE", "Artist fetch");
            }

            @Override
            public void onResponse(@NotNull Call call, @NotNull Response response) throws IOException {
                if(response.isSuccessful())
                    parseData(response.body().string());
                else Log.d("OKHTTP", "Response not successful");
            }
        });
    }

    private void parseData (String queryResponse) {
        try {
            JSONArray artistResponse = new JSONObject(queryResponse).getJSONObject("artists").getJSONArray("artist");

            for(int i = 0; i < artistResponse.length(); i++) {
                JSONObject artist = artistResponse.getJSONObject(i);

                dataSet.add(new ArtistData(artist.getString("mbid"), artist.getString("playcount"), artist.getString("listeners"),
                        artist.getString("name"), artist.getJSONArray("image").getJSONObject(0).getString("#text")));
            }
        } catch (JSONException e) {
            e.printStackTrace();
        }
    }
}

我只是一个初学者，所以现在我基本上是在尝试将来自不同教程的代码合并为一个。这就是为什么你在这里看到的一些东西可能没有意义，所以请告诉我我能解决什么。

Answer 1

Got through this link

首先尝试学习如何使用改造来获取数据，你不会解析数据，它们是一个库 GSON 和 Moshi，它将完成你所有的工作，你只需要使用 POJO。通过这个例子

Answer 2

为了告诉 Recycleview 数据已经到来，您需要获取适配器并设置其数据，然后调用 adapter.notifyDataSetChanged();

 mArtistsViewModel.getArtists().observe(this, new Observer<ArrayList<ArtistData>>() {
            @Override
            public void onChanged(ArrayList<ArtistData> artistData) {
              -->  adapter.setData(artistData); // Something like that 
                adapter.notifyDataSetChanged();
            }
        });

Answer 3

所以要回答这个问题，部分解决方案就像有人建议的那样，将 adapter.setData() 函数添加到我的适配器并在 onChanged() 中调用它。

 mArtistsViewModel.getArtists().observe(this, new Observer<ArrayList<ArtistData>>() {
            @Override
            public void onChanged(ArrayList<ArtistData> artistData) {
              -->  adapter.setData(artistData); // Something like that 
                adapter.notifyDataSetChanged();
            }
        });

第二部分是在我的 repo

的 parseData 函数中添加 data.postValue()

private void parseData (String queryResponse) {
    try {
        JSONArray artistResponse = new JSONObject(queryResponse).getJSONObject("artists").getJSONArray("artist");

        for(int i = 0; i < artistResponse.length(); i++) {
            JSONObject artist = artistResponse.getJSONObject(i);

            dataSet.add(new ArtistData(artist.getString("mbid"), artist.getString("playcount"), artist.getString("listeners"),
                    artist.getString("name"), artist.getJSONArray("image").getJSONObject(0).getString("#text")));
        }
        data.postValue(dataSet); //THIS WAS ADDED
    } catch (JSONException e) {
        e.printStackTrace();
    }
}

这可能不是我在这里所做的最佳解决方案，但它按预期工作。

Recyclerview与OkHttp请求同步

Recyclerview and OkHttp request synchronisation

java

android

synchronization

okhttp

android-recyclerview