Android - 當url image jpg不存在時如何顯示本地默認圖片？

Question

我正在致力於一個Android項目，我從https://www.themoviedb.org/下載信息，包括要在活動中顯示的jpg文件。除了時常的jpg路徑是空的，所有的都在按預期工作，導致一個空白的方形而不是海報。構造的URL的 例如，當JPG可用： http://image.tmdb.org/t/p/w185/3cvZAUVP0gjP0p54TOVXQ50fEyZ.jpg 構造的URL的例子，當一個jpg不可用： http://image.tmdb.org/t/p/w185null

所以我想我可以簡單地與位於本地PNG文件替換空一個我繪製的文件夾，但是我已經嘗試了許多不同的方法，包括指出

if (poster.equals("http://image.tmdb.org/t/p/w185null")) { 
       poster = "@drawable/noposter.png"; 
      } 

但是在android監視器，我可以看到它被認爲是一個字符串。 我閱讀了Android開發人員在代碼中訪問資源部分，但它不包括我的具體需求。

如果需要，我似乎無法顯示默認圖片。

我將不勝感激您的幫助。樓下

是工作，但顯示空方如果沒有JPG可用代碼：

public class GetMoviesInfo extends AsyncTask<String, Void, List<Movies>> { 

public InterfaceAsyncResponse delegate; 
private final String LOGTAG = GetMoviesInfo.class.getSimpleName(); 
private final String API_KEY_HEX_NUM = "a valid key is here in my project"; 
private final String MOVIE_POSTER_BASE_URL = "http://image.tmdb.org/t/p/"; 
private final String CHOSEN_MOVIE_POSTER_SIZE = "w185"; 

public GetMoviesInfo(InterfaceAsyncResponse delegate){ 
    this.delegate = delegate; 
} 

@Override 
protected List<Movies> doInBackground(String... parameters) { 

    if (parameters.length == 0) { 
     return null; 
    } 

    HttpURLConnection urlConnection = null; 
    BufferedReader inputReader = null; 
    String moviesStr = null; 

    try { 

     final String BASEURL = "http://api.themoviedb.org/3/discover/movie?"; 
     final String SORT_BY_KEY = "sort_by"; 
     final String APIKEY = "api_key"; 
     String sortedBy = parameters[0]; 

     Uri buildUri = Uri.parse(BASEURL).buildUpon() 
       .appendQueryParameter(SORT_BY_KEY, sortedBy) 
       .appendQueryParameter(APIKEY, API_KEY_HEX_NUM) 
       .build(); 

     URL url = new URL(buildUri.toString()); 


     urlConnection = (HttpURLConnection) url.openConnection(); 
     urlConnection.setRequestMethod("GET"); 
     urlConnection.connect(); 


     InputStream inputStream = urlConnection.getInputStream(); 
     StringBuffer bufferStr = new StringBuffer(); 
     if (inputStream == null) { 
      return null; 
     } 
     inputReader = new BufferedReader(new InputStreamReader(inputStream)); 

     String inputLine; 
     while ((inputLine = inputReader.readLine()) != null) { 
      bufferStr.append(inputLine + "\n"); 
     } 

     if (bufferStr.length() == 0) { 
      return null; 
     } 
     moviesStr = bufferStr.toString(); 

    } catch (IOException e) { 
     Log.e(LOGTAG, "Error ", e); 
     return null; 
    } finally { 
     if (urlConnection != null) { 
      urlConnection.disconnect(); 
     } 
     if (inputReader != null) { 
      try { 
       inputReader.close(); 
      } catch (final IOException e) { 
       Log.e(LOGTAG, "Error closing stream", e); 
      } 
     } 
    } 

    try { 
     return extractData(moviesStr); 
    } catch (JSONException e) { 
     Log.e(LOGTAG, e.getMessage(), e); 
     e.printStackTrace(); 
    } 
    return null; 
} 



@Override 
protected void onPostExecute(List<Movies> returns) { 
    if (returns != null) { 

     delegate.onTaskCompleted(returns); 
    } 
} 

private String getReleasedYear(String dateReleased){ 
    final SimpleDateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd", Locale.US); 
    final Calendar calendar = Calendar.getInstance(); 
    try { 
     calendar.setTime(dateFormat.parse(dateReleased)); 
    } catch (ParseException e) { 
     e.printStackTrace(); 
    } 
    return Integer.toString(calendar.get(Calendar.YEAR)); 
} 

private List<Movies> extractData(String moviesJsonString) throws JSONException { 

    // Items being extracted 
    final String MOVIES_ARRAY = "results"; 
    final String ORIGINAL_TITLE = "original_title"; 
    final String POSTER_PATH = "poster_path"; 
    final String OVERVIEW = "overview"; 
    final String VOTE_AVERAGE = "vote_average"; 
    final String RELEASED_DATE = "release_date"; 
    final String POPULARITY = "popularity"; 

    JSONObject moviesJson = new JSONObject(moviesJsonString); 
    JSONArray moviesArray = moviesJson.getJSONArray(MOVIES_ARRAY); 
    int moviesLength = moviesArray.length(); 
    List<Movies> movies = new ArrayList<>(); 



    for(int i = 0; i < moviesLength; ++i) { 

     // For each movie, the JSON object create a new movie object 
     JSONObject movie = moviesArray.getJSONObject(i); 
     String title = movie.getString(ORIGINAL_TITLE); 
     String poster = MOVIE_POSTER_BASE_URL + CHOSEN_MOVIE_POSTER_SIZE + movie.getString(POSTER_PATH); 
     Log.i("TAG","From GetMoviesInfo_extractData: "+ poster); 
     String overview = movie.getString(OVERVIEW); 
     String voteAverage = movie.getString(VOTE_AVERAGE); 
     String releasedDate = getReleasedYear(movie.getString(RELEASED_DATE)); 
     String popularity = movie.getString(POPULARITY); 

     movies.add(new Movies(title, poster, overview, voteAverage, releasedDate, popularity)); 
    } 
    return movies; 
} 

}

Answer 1

您可以使用畢加索庫完成自己的目標，它是利用我很簡單分享代碼。 更多信息，使用此http://square.github.io/picasso/

> Picasso.with(context) 
>  .load(url) 
>  .placeholder(R.drawable.user_placeholder) 
>  .error(R.drawable.user_placeholder_error) 
>  .into(imageView);