Previene l'attività di ricarica quando si accede al menu di azione contestuale facendo clic su un'immagine in grigliata asincrona

Question

Ho un sacco di immagini da sdcard che vengono caricate in modo asincrono su una griglia. Tutto funziona bene, ma quando si accede a un menu di azione contestuale a selezione multipla facendo clic su qualsiasi immagine l'intera attività viene ricaricata e tutte le immagini vengono caricate nuovamente. Come prevenirlo?

Myadapter

public class PhotosGridViewImageAdapter extends BaseAdapter { 

AsyncTaskLoadFiles myAsyncTaskLoadFiles; 

public class AsyncTaskLoadFiles extends AsyncTask<Void, String, Void> { 

    File targetDirector; 
    PhotosGridViewImageAdapter myTaskAdapter; 

    public AsyncTaskLoadFiles(PhotosGridViewImageAdapter adapter) { 
     myTaskAdapter = adapter; 
    } 

    @Override 
    protected void onPreExecute() { 
     String ExternalStorageDirectoryPath = Environment 
       .getExternalStorageDirectory().getAbsolutePath(); 
     String targetPath = ExternalStorageDirectoryPath + File.separator + AppConstant.PHOTO_ALBUM + File.separator; 
     targetDirector = new File(targetPath); 
     myTaskAdapter.clear(); 

     super.onPreExecute(); 
    } 

    @Override 
    protected Void doInBackground(Void... params) { 
     File[] files = targetDirector.listFiles(); 
     Arrays.sort(files); 
     for (File file : files) { 
      publishProgress(file.getAbsolutePath()); 
      if (isCancelled()) break; 
     } 
     return null; 
    } 

    @Override 
    protected void onProgressUpdate(String... values) { 
     myTaskAdapter.add(values[0]); 
     super.onProgressUpdate(values); 
    } 

    @Override 
    protected void onPostExecute(Void result) { 
     myTaskAdapter.notifyDataSetChanged(); 
     super.onPostExecute(result); 
    } 

} 

ArrayList<String> itemList = new ArrayList<String>(); 

void add(String path) { 
    itemList.add(path); 
} 

void clear() { 
    itemList.clear(); 
} 

void remove(int index){ 
    itemList.remove(index); 
} 

private Activity _activity; 
private ArrayList<String> _filePaths = new ArrayList<String>(); 
private int imageWidth; 

public PhotosGridViewImageAdapter(Activity activity, ArrayList<String> filePaths, 
     int imageWidth) { 
    this._activity = activity; 
    this._filePaths = filePaths; 
    this.imageWidth = imageWidth; 
} 

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

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

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

@Override 
public View getView(final int position, View convertView, ViewGroup parent) { 
    ViewHolder holder; 
    final ImageView imageView; 
    if (convertView == null) { 
     imageView = new ImageView(_activity); 
     imageView.setScaleType(ImageView.ScaleType.CENTER_CROP); 
     imageView.setLayoutParams(new GridView.LayoutParams(imageWidth, 
       imageWidth)); 

     convertView = imageView; 

     holder = new ViewHolder(); 
     holder.image = imageView; 
     holder.position = position; 
     convertView.setTag(holder); 
    } else { 
     //imageView = (ImageView) convertView; 
     holder = (ViewHolder) convertView.getTag(); 
     ((ImageView)convertView).setImageBitmap(null); 
    } 

    new AsyncTask<ViewHolder, Void, Bitmap>() { 
     private ViewHolder v; 

     // get screen dimensions 
     @Override 
     protected Bitmap doInBackground(ViewHolder... params) { 
      v = params[0]; 
      Bitmap image = decodeFile(_filePaths.get(position), imageWidth, 
        imageWidth); 
      //imageView.setImageBitmap(image); 
      return image; 
     } 
     @Override 
     protected void onPostExecute(Bitmap result) { 
      super.onPostExecute(result); 
      v.image.setImageBitmap(result); 

     } 
    }.execute(holder); 

    return convertView; 
} 

/* 
* Resizing image size 
*/ 
public Bitmap decodeFile(String filePath, int WIDTH, int HEIGHT) { 
    try { 
     File f = new File(filePath); 
     if(filePath.contains(".jpg")) { 
      BitmapFactory.Options o = new BitmapFactory.Options(); 
      o.inJustDecodeBounds = true; 
      BitmapFactory.decodeStream(new FileInputStream(f), null, o); 

      final int REQUIRED_WIDTH = WIDTH; 
      final int REQUIRED_HEIGHT = HEIGHT; 
      int scale = 1; 
      while (o.outWidth/scale/2 >= REQUIRED_WIDTH 
        && o.outHeight/scale/2 >= REQUIRED_HEIGHT) 
       scale *= 2; 

      BitmapFactory.Options o2 = new BitmapFactory.Options(); 
      o2.inSampleSize = scale; 
      return BitmapFactory.decodeStream(new FileInputStream(f), null, o2); 
     }else if(filePath.contains(".mp4")){ 
      return ThumbnailUtils.createVideoThumbnail(filePath, 0); 
     } 
    } catch (FileNotFoundException e) { 
     e.printStackTrace(); 
    } 
    return null; 
} 
class ViewHolder { 
    ImageView image; 
    int position; 
} 
} 

Azione contestuale codice del menu

public class MultiChoiceModeListener implements 
     GridView.MultiChoiceModeListener { 
    public boolean onCreateActionMode(ActionMode mode, Menu menu) { 
     MenuInflater inflater = mode.getMenuInflater(); 
     inflater.inflate(R.menu.contextual_action_menu, menu); 
     //mode.setTitle("Select Items"); 
     mode.setTitle("1 item selected"); 
     return true; 
    } 

    public boolean onPrepareActionMode(ActionMode mode, Menu menu) { 
     return true; 
    } 
    public boolean onActionItemClicked(ActionMode mode, MenuItem item) { 
     // Respond to clicks on the actions in the CAB 
     switch (item.getItemId()) { 
      case R.id.delete: 
       SparseBooleanArray checked = gridView.getCheckedItemPositions(); 
       try { 
        int len = checked.size(); 
        for (int i = 0; i < len; i++) { 
         if (checked.valueAt(i)) { 
          Integer position = checked.keyAt(i); 
          //deleteToMessageHistory(position); 
         } 
        } 
       }catch (Exception i){ 
        Toast.makeText(PhotosGridViewActivity.this, "Message was not deleted. Try again.", Toast.LENGTH_SHORT).show(); 
       } 
       mode.finish(); // Action picked, so close the CAB 
       return true; 
      default: 
       return false; 
     } 
    } 
    public void onDestroyActionMode(ActionMode mode) { 
    } 
    public void onItemCheckedStateChanged(ActionMode mode, int position, 
              long id, boolean checked) { 
     int selectCount = gridView.getCheckedItemCount(); 
     switch (selectCount) { 
      case 1: 
       mode.setTitle("1 item selected"); 
       break; 
      default: 
       mode.setTitle("" + selectCount + " items selected"); 
       break; 
     } 
    } 
} 

Apprezzo tutto l'aiuto!

== AGGIORNAMENTO ==

ecco il codice MainActivity:

public class PhotosGridViewActivity extends Activity { 

private PhotosUtils utils; 
private ArrayList<String> imagePaths = new ArrayList<String>(); 
private PhotosGridViewImageAdapter adapter; 
private GridView gridView; 
private int columnWidth; 

@Override 
protected void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 

    // Initilizing Grid View 
    InitilizeGridLayout(); 

} 

private void InitilizeGridLayout() { 
    setContentView(R.layout.photos_grid_view); 
    utils = new PhotosUtils(PhotosGridViewActivity.this); 
    gridView = (GridView) findViewById(R.id.grid_view); 
    // loading all image paths from SD card 
    imagePaths = utils.getFilePaths(); 
    Resources r = getResources(); 
    float padding = TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, 
      AppConstant.GRID_PADDING, r.getDisplayMetrics()); 

    columnWidth = (int) ((utils.getScreenWidth() - ((AppConstant.NUM_OF_COLUMNS + 1) * padding))/AppConstant.NUM_OF_COLUMNS); 

    gridView.setNumColumns(AppConstant.NUM_OF_COLUMNS); 
    gridView.setColumnWidth(columnWidth); 
    gridView.setStretchMode(GridView.NO_STRETCH); 
    gridView.setPadding((int) padding, (int) padding, (int) padding, 
      (int) padding); 
    gridView.setHorizontalSpacing((int) padding); 
    gridView.setVerticalSpacing((int) padding); 

    gridView.setChoiceMode(GridView.CHOICE_MODE_MULTIPLE_MODAL); 
    gridView.setMultiChoiceModeListener(new MultiChoiceModeListener()); 

    // Gridview adapter 
    adapter = new PhotosGridViewImageAdapter(PhotosGridViewActivity.this, imagePaths, 
      columnWidth); 
    // setting grid view adapter 
    gridView.setAdapter(adapter); 

    gridView.setOnItemClickListener(new AdapterView.OnItemClickListener() { 
     @Override 
     public void onItemClick(AdapterView<?> parent, View v, int position, long id) { 
      gridView.getItemAtPosition(position); 
      Intent i = new Intent(PhotosGridViewActivity.this, PhotosScreenViewActivity.class); 
      i.putExtra("position", position); 
      PhotosGridViewActivity.this.startActivity(i); 
     } 
    }); 
} 

public class MultiChoiceModeListener implements 
     GridView.MultiChoiceModeListener { 
    public boolean onCreateActionMode(ActionMode mode, Menu menu) { 
     MenuInflater inflater = mode.getMenuInflater(); 
     inflater.inflate(R.menu.contextual_action_menu, menu); 
     //mode.setTitle("Select Items"); 
     mode.setTitle("1 item selected"); 
     return true; 
    } 

    public boolean onPrepareActionMode(ActionMode mode, Menu menu) { 
     return true; 
    } 
    public boolean onActionItemClicked(ActionMode mode, MenuItem item) { 
     // Respond to clicks on the actions in the CAB 
     switch (item.getItemId()) { 
      case R.id.delete: 
       SparseBooleanArray checked = gridView.getCheckedItemPositions(); 
       try { 
        int len = checked.size(); 
        for (int i = 0; i < len; i++) { 
         if (checked.valueAt(i)) { 
          Integer position = checked.keyAt(i); 
          //deleteToMessageHistory(position); 
         } 
        } 
       }catch (Exception i){ 
        Toast.makeText(PhotosGridViewActivity.this, "Message was not deleted. Try again.", Toast.LENGTH_SHORT).show(); 
       } 
       mode.finish(); // Action picked, so close the CAB 
       return true; 
      default: 
       return false; 
     } 
    } 
    public void onDestroyActionMode(ActionMode mode) { 
    } 
    public void onItemCheckedStateChanged(ActionMode mode, int position, 
              long id, boolean checked) { 
     int selectCount = gridView.getCheckedItemCount(); 
     switch (selectCount) { 
      case 1: 
       mode.setTitle("1 item selected"); 
       break; 
      default: 
       mode.setTitle("" + selectCount + " items selected"); 
       break; 
     } 
    } 
} 

@Override 
public boolean onCreateOptionsMenu(Menu menu) { 
    // Inflate the menu; this adds items to the action bar if it is present. 
    getMenuInflater().inflate(co.glurl.appoid.R.menu.photo_gallery, menu); 
    return true; 
} 
@Override 
public boolean onOptionsItemSelected(MenuItem item) { 
    switch (item.getItemId()) { 
     case R.id.add: 
      /** Go to the user's add photos. */ 
      startActivity(new Intent(this, PhotoIntentActivity.class)); 
      break; 
     //case R.id.settings: 
      /** Go to the user's settings photos. */ 
     // startActivity(new Intent(this, PhotoGridSettings.class)); 
     // break; 
     default: 
      return super.onContextItemSelected(item); 
    } 
    return true; 
} 

} 

Answer 1

mio soluction. Grazie a @pushbit per avermi guidato attraverso di esso.

@Override 
public View getView(final int position, View convertView, ViewGroup parent) { 
    ImageView imageView = (ImageView) convertView; 
    if (imageView == null) { 
     imageView = new ImageView(_activity); 
    } 

    // Trigger the download of the URL asynchronously into the image view. 
    if(_filePaths.get(position).contains(".jpg")) { 
     Picasso.with(_activity) 
       .load(new File(_filePaths.get(position))) 
       .resize(imageWidth, imageWidth) 
       .centerCrop() 
       .tag(_activity) 
       .into(imageView); 
    }else if(_filePaths.get(position).contains(".mp4")){ 
     VideoRequestHandler videoRequestHandler; 
     Picasso picassoInstance; 
     videoRequestHandler=new VideoRequestHandler(); 
     picassoInstance = new Picasso.Builder(_activity.getApplicationContext()) 
       .addRequestHandler(videoRequestHandler) 
       .build(); 
     picassoInstance 
       .load(videoRequestHandler.SCHEME_VIDEO+":"+_filePaths.get(position)) 
       .resize(imageWidth, imageWidth) 
       .centerCrop() 
       .tag(_activity) 
       .into(imageView); 
    } 
    return imageView; 
} 

public static boolean deleteToPhotoAlbum(Integer position) { 
    File file = new File(_filePaths.get(position)); 
    boolean deleted = file.delete(); 
    return deleted; 
} 

public class VideoRequestHandler extends RequestHandler { 
    public String SCHEME_VIDEO = "video"; 
    @Override 
    public boolean canHandleRequest(Request data) 
    { 
     String scheme = data.uri.getScheme(); 
     return (SCHEME_VIDEO.equals(scheme)); 
    } 

    @Override 
    public Result load(Request data, int arg1) throws IOException 
    { 
     Bitmap bm = ThumbnailUtils.createVideoThumbnail(data.uri.getPath(), MediaStore.Images.Thumbnails.MINI_KIND); 
     return new Result(bm, Picasso.LoadedFrom.DISK); 
    } 
}