android 中的 AsyncTaskLoader 问题

Question

您好，我在我的应用程序中使用了 AsyncTaskLoader，并且我已经在 MovieTaskLoader class 中实现了它，但是当我在我的片段中实现 Loader 回调时，我在 onCreateLoader() 方法中遇到了类型转换错误。 MovieTaskLoader class:

class MovieTaskLoader extends AsyncTaskLoader<ArrayList<Movies>> {


MovieTaskLoader(Context context) {
    super(context);
}

@Override
protected void onStartLoading() {
    forceLoad();
}

@Override
public ArrayList<Movies> loadInBackground() {

    //Building URL
    URL url = null;
    String jsonData = null;
    Uri uri = Uri.parse(Utility.BASE_URL).buildUpon()
            .appendPath("popular")
            .appendQueryParameter("api_key", BuildConfig.api_key)
            .build();
    try {
        url = new URL(uri.toString());
    } catch (MalformedURLException e) {
        e.printStackTrace();
    }

    //Downloading json data
    HttpURLConnection urlConnection;

    try {
        assert url != null;
        urlConnection = (HttpURLConnection) url.openConnection();
        if(urlConnection.getResponseCode() == HttpURLConnection.HTTP_OK){
            jsonData = readStream(urlConnection.getInputStream());
        }
    } catch (IOException e) {
        e.printStackTrace();
    }

    return getMovieData(jsonData);
}

private String readStream(InputStream in) {
    BufferedReader reader = null;
    StringBuilder response = new StringBuilder();
    try {
        reader = new BufferedReader(new InputStreamReader(in));
        String line;
        while ((line = reader.readLine()) != null) {
            response.append(line);
        }
    } catch (IOException e) {
        e.printStackTrace();
    } finally {
        if (reader != null) {
            try {
                reader.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
    return response.toString();
}

private ArrayList<Movies> getMovieData(String jsonData){
    ArrayList<Movies> movies = new ArrayList<>();
    try {
        JSONObject jsonObject = new JSONObject(jsonData);
        JSONArray results = jsonObject.getJSONArray("results");
        for(int i=0; i<20; i++){
            Movies movie = new Movies();
            JSONObject object = results.getJSONObject(i);
            movie.setTitle(object.getString("title"));
            movie.setSynopsis("overview");
            movie.setVote_avg("vote_average");
            movie.setDate("release_date");
            movies.add(movie);
        }
    } catch (JSONException e) {
        e.printStackTrace();
    }
    return movies;
}
}

片段class:

public class PopularFragment extends Fragment implements LoaderManager.LoaderCallbacks<ArrayList<Movies>> {


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


@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {
    // Inflate the layout for this fragment
    View view = inflater.inflate(R.layout.fragment_popular, container, false);

    RecyclerView popularView = (RecyclerView) view.findViewById(R.id.popular_view);
    GridLayoutManager layoutManager = new GridLayoutManager(getContext(), 2);
    popularView.setLayoutManager(layoutManager);
    popularView.setAdapter(new RecyclerViewAdapter());

    return view;
}

@Override
public Loader<ArrayList<Movies>> onCreateLoader(int id, Bundle args) {
    return new MovieTaskLoader(getContext());
}

@Override
public void onLoadFinished(Loader<ArrayList<Movies>> loader, ArrayList<Movies> data) {

}

@Override
public void onLoaderReset(Loader<ArrayList<Movies>> loader) {

}
}

我在 onCreateLoader() 方法中遇到错误，类型转换错误是：

必填："Loader"

找到：MovieTaskLoader

Answer 1

检查您的导入。确保两者都是相同的版本

android.support.v4.content.AsyncTaskLoader<D> 
android.support.v4.app.LoaderManager.LoaderCallbacks<D>

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