我如何重写我的方法来返回一个列表或Movie而不是字符串列表?

Question

我想重写我的方法，使它返回一个List of Movie类，而不是一个List of String类，这是我想改变的方法:

private List<String> getMovieDataFromJson(String forecastJsonStr)
            throws JSONException {
        JSONObject movieJson = new JSONObject(forecastJsonStr);
        JSONArray movieArray = movieJson.getJSONArray("results");
        List<String> urls = new ArrayList<>();
        for (int i = 0; i < movieArray.length(); i++) {
            JSONObject movie = movieArray.getJSONObject(i);
            urls.add("http://image.tmdb.org/t/p/w185" + movie.getString("poster_path"));
        }
        return urls;
    }

我试着这样重写:

  private List<Movie> getMovieDataFromJson(String forecastJsonStr)
                throws JSONException {
            JSONObject movieJson = new JSONObject(forecastJsonStr);
            JSONArray movieArray = movieJson.getJSONArray("results");
            List<Movie> movies = new ArrayList<>();
            for (int i = 0; i < movieArray.length(); i++) {
                JSONObject movie = movieArray.getJSONObject(i);
                Movie movie1 = new Movie(movie.getString("original_title"), movie.getDouble("vote_average"), movie.getString("release_date"), movie.getString("overview"), movie.getString("poster_path"));
                movies.add(movie1);
            }
            return movies;
        }

但问题是我得到错误在139行，它说需要的是字符串，但发现电影。这是139行返回getMovieDataFromJson (movieJsonStr);

下面是我的代码:

package com.projmobileapp.pmdbadd.pmdb;

import android.content.Context;
import android.os.AsyncTask;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuInflater;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.GridView;
import android.widget.ImageView;
import com.squareup.picasso.Picasso;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.URL;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
public class MainActivityFragment extends Fragment {
    //ArrayAdapter<String> mMovieAdapter;
    //String[] movieId,movieTitle,movieOverview,movieReleaseDate,movieVoteAverage;
    String[] moviePosterPath = new String[0];
    public MainActivityFragment() {
    }
    MovieAdapter mMovieAdapter;
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        View rootView = inflater.inflate(R.layout.fragment_main, container, false);
        mMovieAdapter = new MovieAdapter(getActivity());
        GridView listView = (GridView) rootView.findViewById(R.id.gridview_movie);
        listView.setAdapter(mMovieAdapter);
        updateMovie();
        return rootView;
    }
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setHasOptionsMenu(true);
    }
    @Override
    public void onCreateOptionsMenu(Menu menu, MenuInflater inflater) {
        // Inflate the menu; this adds items to the action bar if it is present.
        inflater.inflate(R.menu.mainactivityfragment, menu);
    }
    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        int id = item.getItemId();
        if (id == R.id.action_refresh) {
            updateMovie();
            return true;
        }
        return super.onOptionsItemSelected(item);
    }
    private void updateMovie() {
        FetchMovieTask movieTask = new FetchMovieTask();
        movieTask.execute();
    }
    class FetchMovieTask extends AsyncTask<Void, Void, List<String>> {
        private final String LOG_TAG = FetchMovieTask.class.getSimpleName();
        @Override
        protected List<String> doInBackground(Void... params) {
            HttpURLConnection urlConnection = null;
            BufferedReader reader = null;
            // Will contain the raw JSON response as a string.
            String movieJsonStr = null;
            try {
                URL url = new URL("http://api.themoviedb.org/3/discover/movie?sort_by=popularity.desc&api_key=INSERTAPIKEY");
                urlConnection = (HttpURLConnection) url.openConnection();
                urlConnection.setRequestMethod("GET");
                urlConnection.connect();
                // Read the input stream into a String
                InputStream inputStream = urlConnection.getInputStream();
                StringBuffer buffer = new StringBuffer();
                if (inputStream == null) {
                    // Nothing to do.
                    return null;
                }
                reader = new BufferedReader(new InputStreamReader(inputStream));
                String line;
                while ((line = reader.readLine()) != null) {
                    buffer.append(line + "n");
                }
                if (buffer.length() == 0) {
                    // Stream was empty.  No point in parsing.
                    return null;
                }
                movieJsonStr = buffer.toString();
            } catch (IOException e) {
                Log.e(LOG_TAG, "Error ", e);
                return null;
            } finally {
                if (urlConnection != null) {
                    urlConnection.disconnect();
                }
                if (reader != null) {
                    try {
                        reader.close();
                    } catch (final IOException e) {
                        Log.e(LOG_TAG, "Error closing stream", e);
                    }
                }
            }
            try {
                return getMovieDataFromJson(movieJsonStr);
            } catch (JSONException j) {
                Log.e(LOG_TAG, "JSON Error", j);
            }
            return null;
        }
        private List<String> getMovieDataFromJson(String forecastJsonStr)
                throws JSONException {
            JSONObject movieJson = new JSONObject(forecastJsonStr);
            JSONArray movieArray = movieJson.getJSONArray("results");
            List<String> urls = new ArrayList<>();
            for (int i = 0; i < movieArray.length(); i++) {
                JSONObject movie = movieArray.getJSONObject(i);
                urls.add("http://image.tmdb.org/t/p/w185" + movie.getString("poster_path"));
            }
            return urls;
        }


        @Override
        protected void onPostExecute(List<String> strings) {
            mMovieAdapter.replace(strings);
        }
    }
    class MovieAdapter extends BaseAdapter {
        private final String LOG_TAG = MovieAdapter.class.getSimpleName();
        private final Context context;
        private final List<String> urls = new ArrayList<String>();
        public MovieAdapter(Context context) {
            this.context = context;
            Collections.addAll(urls, moviePosterPath);
        }
        @Override
        public View getView(int position, View convertView, ViewGroup parent) {
            if (convertView == null) {
                convertView = new ImageView(context);
            }
            ImageView imageView = (ImageView) convertView;

            String url = getItem(position);
            Log.e(LOG_TAG, " URL " + url);
            Picasso.with(context).load(url).into(imageView);
            return convertView;
        }
        @Override
        public int getCount() {
            return urls.size();
        }
        @Override
        public String getItem(int position) {
            return urls.get(position);
        }
        @Override
        public long getItemId(int position) {
            return position;
        }
        public void replace(List<String> urls) {
            this.urls.clear();
            this.urls.addAll(urls);
            notifyDataSetChanged();
        }
    }
}

Answer 1

这里的问题是您的AsyncTask将doInBackground()的结果类型定义为List<String>。您需要更改行:

class FetchMovieTask extends AsyncTask<Void, Void, List<String>>

class FetchMovieTask extends AsyncTask<Void, Void, List<Movie>>

并将doInBackground()更改为返回List<Movie>