Какой класс Android генерирует миниатюры музыкальных альбомов?

Question

Я пытаюсь узнать, как андроид MediaStore/MediaScanner создает миниатюры музыкальных альбомов. Я искал источники MediaStore.java и MediaScanner.java, но ничего не нашел.

Вы знаете, где я могу найти соответствующий код? Благодарю.

Answer 1

MediaProvider.java содержит методы, которые используются для создания эскизов альбомов и сохранения их в SD-карте.

https://android.googlesource.com/platform/packages/providers/MediaProvider/+/android-4.4.2_r2/src/com/android/providers/media/MediaProvider.java

private ParcelFileDescriptor makeThumbInternal(ThumbData d) { 
    byte[] compressed = getCompressedAlbumArt(getContext(), d.path); 
    if (compressed == null) { 
     return null; 
    } 
    Bitmap bm = null; 
    boolean need_to_recompress = true; 
    try { 
     // get the size of the bitmap 
     BitmapFactory.Options opts = new BitmapFactory.Options(); 
     opts.inJustDecodeBounds = true; 
     opts.inSampleSize = 1; 
     BitmapFactory.decodeByteArray(compressed, 0, compressed.length, opts); 
     // request a reasonably sized output image 
     final Resources r = getContext().getResources(); 
     final int maximumThumbSize = r.getDimensionPixelSize(R.dimen.maximum_thumb_size); 
     while (opts.outHeight > maximumThumbSize || opts.outWidth > maximumThumbSize) { 
      opts.outHeight /= 2; 
      opts.outWidth /= 2; 
      opts.inSampleSize *= 2; 
     } 
     if (opts.inSampleSize == 1) { 
      // The original album art was of proper size, we won't have to 
      // recompress the bitmap later. 
      need_to_recompress = false; 
     } else { 
      // get the image for real now 
      opts.inJustDecodeBounds = false; 
      opts.inPreferredConfig = Bitmap.Config.RGB_565; 
      bm = BitmapFactory.decodeByteArray(compressed, 0, compressed.length, opts); 
      if (bm != null && bm.getConfig() == null) { 
       Bitmap nbm = bm.copy(Bitmap.Config.RGB_565, false); 
       if (nbm != null && nbm != bm) { 
        bm.recycle(); 
        bm = nbm; 
       } 
      } 
     } 
    } catch (Exception e) { 
    } 
    if (need_to_recompress && bm == null) { 
     return null; 
    } 
    if (d.albumart_uri == null) { 
     // this one doesn't need to be saved (probably a song with an unknown album), 
     // so stick it in a memory file and return that 
     try { 
      return ParcelFileDescriptor.fromData(compressed, "albumthumb"); 
     } catch (IOException e) { 
     } 
    } else { 
     // This one needs to actually be saved on the sd card. 
     // This is wrapped in a transaction because there are various things 
     // that could go wrong while generating the thumbnail, and we only want 
     // to update the database when all steps succeeded. 
     d.db.beginTransaction(); 
     Uri out = null; 
     ParcelFileDescriptor pfd = null; 
     try { 
      out = getAlbumArtOutputUri(d.helper, d.db, d.album_id, d.albumart_uri); 
      if (out != null) { 
       writeAlbumArt(need_to_recompress, out, compressed, bm); 
       getContext().getContentResolver().notifyChange(MEDIA_URI, null); 
       pfd = openFileHelper(out, "r"); 
       d.db.setTransactionSuccessful(); 
       return pfd; 
      } 
     } catch (IOException ex) { 
      // do nothing, just return null below 
     } catch (UnsupportedOperationException ex) { 
      // do nothing, just return null below 
     } finally { 
      d.db.endTransaction(); 
      if (bm != null) { 
       bm.recycle(); 
      } 
      if (pfd == null && out != null) { 
       // Thumbnail was not written successfully, delete the entry that refers to it. 
       // Note that this only does something if getAlbumArtOutputUri() reused an 
       // existing entry from the database. If a new entry was created, it will 
       // have been rolled back as part of backing out the transaction. 
       getContext().getContentResolver().delete(out, null, null); 
      } 
     } 
    } 
    return null; 
}