Android 通过更改菜单中的请求URL对JSON数组排序

我目前正在显示一个JSON查询中的项目列表，但希望实现一种通过菜单对结果进行排序的方法。我尝试使用的两个排序参数是按受欢迎程度排序和按平均评级排序。我试图通过更改查询结果的URL来实现这一点，因为api查询具有用于显示基于流行度和平均评级的JSON数据的参数。我尝试过在单击菜单项时实现此购买，但该活动不会填充新结果。URL会更改，但不会显示新结果。任何帮助或暗示都将不胜感激

主要活动：

public class MainActivity extends AppCompatActivity {

public static final String TAG = "MainActivity";

//Declare some of the objects we are using.
String SEARCH_TERM = "popularity.desc";
private RecyclerView mRecyclerView;

//GridLayoutManage will allow us to load our items in a grid.
private GridLayoutManager gridLayoutManager;

//Custoj Adapter lets us bind out data from the web server with our recylerview
private MovieAdapter mMovieAdapter;

//Need a list to store the data from the server.
private List<Movie> movieData;

/*
API KEY
https://api.themoviedb.org/3/movie/550?api_key=1f5029b7d824dee72f4d4a156dac90ed
 */

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    //Reference the RecyclerView
    mRecyclerView = findViewById(R.id.recycler_view);

    //Reference the list.  This needs to be done before setting the adapter to the recycler
    //view or the app will think there is an empty list.
    movieData = new ArrayList<>();

    //To update the list with items, we create a new method to do that.
    loadMovieData();

    //Create a new grid layout manager in order to display data to a grid.
    gridLayoutManager = new GridLayoutManager(this, 3);
    mRecyclerView.setLayoutManager(gridLayoutManager);

    //Bind the data we receive from the web server to the recyclerview itself.
    mMovieAdapter = new MovieAdapter(this, movieData);

    //Apply the adapter to the recyclerview.
    mRecyclerView.setAdapter(mMovieAdapter);

}

//Tell the new method to get the dat abased on the search term within the url.
private void loadMovieData() {
    new FetchMovieTask().execute(SEARCH_TERM);
}

//Inflate the menu
@Override
public boolean onCreateOptionsMenu(Menu menu) {
    MenuInflater inflater = getMenuInflater();
    inflater.inflate(R.menu.main_menu, menu);
    return true;
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    switch (item.getItemId()) {
        case R.id.sort_by_most_popular:
            SEARCH_TERM = "popularity.desc";
            loadMovieData();
            mMovieAdapter.notifyDataSetChanged();
            return true;
        case R.id.sort_by_highest_rated:
            SEARCH_TERM = "popularity.asc";
            loadMovieData();
            mMovieAdapter.notifyDataSetChanged();
            return true;
        default:
            return super.onOptionsItemSelected(item);
    }
}

//We need to use an AsyncTask to perform the request to get the data.  The first argument
//we use a String because this will allow us to pass the url.
public class FetchMovieTask extends AsyncTask<String, Void, Void> {

    @Override
    protected Void doInBackground(String... strings) {

        final String MOVIES_RESULTS = "results";
        final String MOVIES_POSTER_IMAGE = "poster_path";
        final String MOVIES_TITLE = "title";
        final String RELEASE_DATE = "release_date";
        final String VOTE_AVERAGE = "vote_average";
        final String PLOT = "overview";

        //Create the network request to download the JSON data from the url database.
        URL moviesUrl = NetworkUtils.buildUrl(SEARCH_TERM);
        try {
            //The response we get is in the form of JSON.
            String jsonMoviesResponse = NetworkUtils.getReponseFromHttpUrl(moviesUrl);

            //A new JSON object created from the JSON response.
            JSONObject moviesJson = new JSONObject(jsonMoviesResponse);

            //Read the movie results array from the JSON object.
            JSONArray moviesArray = moviesJson.getJSONArray(MOVIES_RESULTS);

            //A loop is created to read the array and add the data we need to a list.
            for (int i = 0; i < moviesArray.length(); i++) {

                String moviePoster;
                String movieTitle;
                String movieReleaseDate;
                String voteAverage;
                String plot;
                JSONObject movie = moviesArray.getJSONObject(i);

                moviePoster = ("http://image.tmdb.org/t/p/w185/" + movie.getString(MOVIES_POSTER_IMAGE));
                movieTitle = movie.getString(MOVIES_TITLE);
                movieReleaseDate = movie.getString(RELEASE_DATE);
                voteAverage = movie.getString(VOTE_AVERAGE);
                plot = movie.getString(PLOT);

                Movie data = new Movie(movieTitle, movieReleaseDate, moviePoster, voteAverage, plot);

                //Add the data items to our movieData list.
                movieData.add(data);
            }

        } catch (JSONException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
        return null;
    }

    //This is called when the network request is done.  We use this method to tell our
    //custom adapter that there is a change in the data list so that it can load new cardview
    //widgets in the list.
    @Override
    protected void onPostExecute(Void aVoid) {
        mMovieAdapter.notifyDataSetChanged();
    }
}

公共类NetworkUtils{

//These utilities will be used to communicate with the servers.
private static final String TAG = NetworkUtils.class.getSimpleName();

private static final String BASE_URL = "https://api.themoviedb.org/3/discover/movie";
private static final String API_KEY = "1f5029b7d824dee72f4d4a156dac90ed";

//This builds the URL used to talk to movie database.
public static URL buildUrl(String SEARCH_TERM) {
    Uri builtUri = Uri.parse(BASE_URL).buildUpon()
            .appendQueryParameter("api_key",API_KEY)
            .appendQueryParameter("sort_by", SEARCH_TERM)
            .build();

    URL url = null;
    try {
        url = new URL(builtUri.toString());
    } catch (MalformedURLException e) {
        e.printStackTrace();
    }

    Log.v(TAG, "Built URL " + url);

    return url;
}

//This method returns the entire result from the HTTP response.
public static String getReponseFromHttpUrl(URL url) throws IOException {
    HttpURLConnection urlConnection = (HttpURLConnection) url.openConnection();
    try {
        InputStream inputStream = urlConnection.getInputStream();

        Scanner scanner = new Scanner(inputStream);
        scanner.useDelimiter("\\A");

        boolean hasInput = scanner.hasNext();
        if (hasInput) {
            return scanner.next();
        } else {
            return null;
        }
    } finally {
        urlConnection.disconnect();

    }
}

---

}

如果我是对的，在添加新电影之前，您没有清理电影阵列，因此新获取的项目必须位于该列表的末尾。 在AsyncTask的

onPreExecute（）

上，您应该调用

movieData.clear（）；mMovieAdapter.notifyDataSetChanged（）

希望有帮助
 真是太棒了！我删除了notifyDataSetChanged部分，因为它导致应用程序崩溃，但清除数据有效！在获取数据之前初始化适配器，错误应该消失！
//These utilities will be used to communicate with the servers.
private static final String TAG = NetworkUtils.class.getSimpleName();

private static final String BASE_URL = "https://api.themoviedb.org/3/discover/movie";
private static final String API_KEY = "1f5029b7d824dee72f4d4a156dac90ed";

//This builds the URL used to talk to movie database.
public static URL buildUrl(String SEARCH_TERM) {
    Uri builtUri = Uri.parse(BASE_URL).buildUpon()
            .appendQueryParameter("api_key",API_KEY)
            .appendQueryParameter("sort_by", SEARCH_TERM)
            .build();

    URL url = null;
    try {
        url = new URL(builtUri.toString());
    } catch (MalformedURLException e) {
        e.printStackTrace();
    }

    Log.v(TAG, "Built URL " + url);

    return url;
}

//This method returns the entire result from the HTTP response.
public static String getReponseFromHttpUrl(URL url) throws IOException {
    HttpURLConnection urlConnection = (HttpURLConnection) url.openConnection();
    try {
        InputStream inputStream = urlConnection.getInputStream();

        Scanner scanner = new Scanner(inputStream);
        scanner.useDelimiter("\\A");

        boolean hasInput = scanner.hasNext();
        if (hasInput) {
            return scanner.next();
        } else {
            return null;
        }
    } finally {
        urlConnection.disconnect();

    }
}