android listview asynctask для textview и imageview

Question

Я пытаюсь создать андроид listview из google book api call, google books api call return данные JSON, которое является одним из этих свойств, является url для миниатюры книги, поэтому я думал о запуская первую асинтаску, которая вызовет API-интерфейс JSON google books, а затем onPostExecute, я запустим вторую асинтезу, которая будет извлекать миниатюры и устанавливать их в изображение, однако поведение неверно, а эскизы не связаны с правильной строкой в listview при извлечении эскизов обновляется только изображение в первой строке, и когда загрузка завершается, заказ перепутан.

ниже выдержка из моего кода:

private class BookSearchListAdapter extends BaseAdapter { 
    private ArrayList<Book> mBooks = new ArrayList<>(); 
    private LayoutInflater mLayoutInflater; 

    public BookSearchListAdapter(Context c, ArrayList<Book> books) { 
     mLayoutInflater = LayoutInflater.from(c); 
     this.mBooks = books; 
    } 

    @Override 
    public View getView(int position, View convertView, ViewGroup parent) { 
     ViewHolder holder; 
     if (convertView == null) { 
      convertView = mLayoutInflater.inflate(R.layout.view_book_search_row, null); 
      holder = new ViewHolder(); 
      holder.mImageView = (ImageView) convertView.findViewById(R.id.book_cover_thumbnail); 
      holder.mTitleTextView = (TextView) convertView.findViewById(R.id.book_title); 
      holder.mAuthorTextView = (TextView) convertView.findViewById(R.id.book_author); 
      convertView.setTag(holder); 
     } else { 
      holder = (ViewHolder) convertView.getTag(); 
     } 
     Book b = mBooks.get(position); 
     holder.mAuthorTextView.setText(TextUtils.join(", ", b.getAuthors())); 
     holder.mTitleTextView.setText(b.getTitle()); 
     if (!b.getThumbnail().equalsIgnoreCase("")) { 
      new ThumbNailDownloaderTask(holder.mImageView).execute(b.getThumbnail()); 
     } 

     return convertView; 
    } 

    @Override 
    public int getCount() { 
     return mBooks.size(); 
    } 

    @Override 
    public Object getItem(int position) { 
     return mBooks.get(position); 
    } 

    @Override 
    public long getItemId(int position) { 
     return position; 
    } 
} 

private static class ViewHolder { 
    ImageView mImageView; 
    TextView mTitleTextView; 
    TextView mAuthorTextView; 
} 

private class SearchBookTask extends AsyncTask<String, Void, String> { 

    private final String TAG = "SearchBookTask"; 

    private ArrayList<Book> mBooks = new ArrayList<>(); 

    private final static String BOOK_ITEMS_KEY = "items"; 
    private final static String BOOK_VOLUMEINFO_KEY = "volumeInfo"; 
    private final static String BOOK_IMAGELINKS_KEY = "imageLinks"; 
    private final static String BOOK_ID_KEY = "id"; 
    private final static String BOOK_TITLE_KEY = "title"; 
    private final static String BOOK_AUTHORS_KEY = "authors"; 
    private final static String BOOK_DESCRIPTION_KEY = "description"; 
    private final static String BOOK_THUMBNAIL_KEY = "thumbnail"; 

    @Override 
    protected String doInBackground(String... params) { 
     String bookQuery = params[0]; 
     String url = Uri.parse(ENDPOINT).buildUpon() 
       .appendQueryParameter("q", bookQuery) 
       .appendQueryParameter("maxResults", "10") 
       .appendQueryParameter("key", API_KEY) 
       .build().toString(); 
     String result = new GoogleFetcher().getUrl(url); 
     return result; 
    } 

    @Override 
    protected void onPreExecute() { 
     mEmptyTextView.setVisibility(View.GONE); 
     mProgressBar.setVisibility(View.VISIBLE); 
    } 

    @Override 
    protected void onPostExecute(String s) { 
     if (s != null) { 
      mProgressBar.setVisibility(View.GONE); 
      constructBooksFromJSONResponse(s); 
      mSearchResultListView.setAdapter(new BookSearchListAdapter(getActivity(), mBooks)); 
     } 
    } 

    @Override 
    protected void onCancelled() { 
     mProgressBar.setVisibility(View.GONE); 
    } 

    private void constructBooksFromJSONResponse(String jsonResponse) { 
     try { 
      JSONObject obj = new JSONObject(new JSONTokener(jsonResponse)); 
      JSONArray jsonArray = obj.getJSONArray(BOOK_ITEMS_KEY); 
      for (int i = 0; i < jsonArray.length(); i++) { 
       JSONObject currentObj = jsonArray.getJSONObject(i); 

       String bookId = ""; 
       if (currentObj.has(BOOK_ID_KEY)) { 
        bookId = currentObj.getString(BOOK_ID_KEY); 
       } 

       JSONObject volumeInfo = currentObj.getJSONObject(BOOK_VOLUMEINFO_KEY); 
       String bookTitle = ""; 
       if (volumeInfo.has(BOOK_TITLE_KEY)) { 
        bookTitle = volumeInfo.getString(BOOK_TITLE_KEY); 
       } 

       JSONArray bookAuthors = new JSONArray(); 
       if (volumeInfo.has(BOOK_AUTHORS_KEY)) { 
        bookAuthors = volumeInfo.getJSONArray(BOOK_AUTHORS_KEY); 
       } 
       ArrayList<String> authors = new ArrayList<>(); 
       if (bookAuthors != null) { 
        for (int j = 0; j < bookAuthors.length(); j++) { 
         authors.add(bookAuthors.getString(j)); 
        } 
       } 

       String bookDescription = ""; 
       if (volumeInfo.has(BOOK_DESCRIPTION_KEY)) { 
        bookDescription = volumeInfo.getString(BOOK_DESCRIPTION_KEY); 
       } 

       JSONObject imageLinks = volumeInfo.getJSONObject(BOOK_IMAGELINKS_KEY); 
       String bookThumbnail = ""; 
       if (imageLinks.has(BOOK_THUMBNAIL_KEY)) { 
        bookThumbnail = imageLinks.getString(BOOK_THUMBNAIL_KEY); 
       } 

       Book b = new Book(bookId, authors, bookTitle, bookDescription, bookThumbnail); 
       mBooks.add(b); 
      } 
     } catch (JSONException e) { 
      mBooks.clear(); 
     } 
    } 
} 

private class ThumbNailDownloaderTask extends AsyncTask<String, Void, Bitmap> { 

    private final WeakReference<ImageView> imageViewReference; 

    private ThumbNailDownloaderTask(ImageView imageView) { 
     imageViewReference = new WeakReference<ImageView>(imageView); 
    } 

    @Override 
    protected Bitmap doInBackground(String... params) { 
     return downloadBitmap(params[0]); 
    } 

    private Bitmap downloadBitmap(String param) { 
     HttpURLConnection urlConnection = null; 
     try { 
      URL url = new URL(param); 
      urlConnection = (HttpURLConnection) url.openConnection(); 
      int statusCode = urlConnection.getResponseCode(); 
      if (statusCode != HttpURLConnection.HTTP_OK) { 
       return null; 
      } 
      InputStream in = urlConnection.getInputStream(); 
      if (in != null) { 
       Bitmap bitmap = BitmapFactory.decodeStream(in); 
       return bitmap; 
      } 
     } catch (IOException e) { 
      if (urlConnection != null) { 
       urlConnection.disconnect(); 
      } 
     } finally { 
      if (urlConnection != null) { 
       urlConnection.disconnect(); 
      } 
     } 
     return null; 
    } 

    @Override 
    protected void onPostExecute(Bitmap bitmap) { 
     if (isCancelled()) { 
      bitmap = null; 
     } 

     if (imageViewReference != null) { 
      ImageView imageView = imageViewReference.get(); 
      if (imageView != null) { 
       if (bitmap != null) { 
        imageView.setVisibility(View.VISIBLE); 
        imageView.setImageBitmap(bitmap); 
       } 
      } 
     } 
    } 
} 

и кнопка поиска, которая запускает поиск является то, следующим образом:

@Override 
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) { 
    View v = inflater.inflate(R.layout.fragment_addbook, container, false); 

    mSearchEditText = (EditText) v.findViewById(R.id.book_title_search_field); 
    mSearchButton = (Button) v.findViewById(R.id.search_button); 
    mSearchButton.setOnClickListener(new View.OnClickListener() { 
     @Override 
     public void onClick(View v) { 
      String bookQuery = mSearchEditText.getText().toString(); 
      new SearchBookTask().execute(bookQuery); 
     } 
    }); 
return v; 
} 

Answer 1

Вы можете попробовать использовать NetworkImageView из Volley библиотеки. Узнайте больше о его image cache. Вы можете найти приличный учебник here и here. Это должно привести к неправильному обращению с вашими фотографиями ListView.