Uri originalUri = MediaStore.Images.Media.EXTERNAL_CONTENT_URI;
                //若為視頻則為MediaStore.Video.Media.EXTERNAL_CONTENT_URI; 
                ContentResolver cr = this.getContentResolver();
                Cursor cursor = cr.query(originalUri, null, null, null, null);
                if (cursor == null) {
                    return;
                }
                for (cursor.moveToFirst();!cursor.isAfterLast(); cursor.moveToNext()) {
                    long thumbNailsId = cursor.getLong(cursor   .getColumnIndex("_ID"));
                    Bitmap bitmap = MediaStore.Images.Thumbnails.getThumbnail(cr,
                            thumbNailsId, Video.Thumbnails.MICRO_KIND, null);
                    //若為視頻則為 
//                  Bitmap bitmap = MediaStore.Video.Thumbnails.getThumbnail(cr, 
//                          thumbNailsId, Video.Thumbnails.MICRO_KIND, null); 
                    return bitmap;
                }

Uri originalUri = MediaStore.Images.Media.EXTERNAL_CONTENT_URI;
    //若為視頻則為MediaStore.Video.Media.EXTERNAL_CONTENT_URI;
    ContentResolver cr = this.getContentResolver();
    Cursor cursor = cr.query(originalUri, null, null, null, null);
    if (cursor == null) {
     return;
    }
    for (cursor.moveToFirst();!cursor.isAfterLast(); cursor.moveToNext()) {
     long thumbNailsId = cursor.getLong(cursor .getColumnIndex("_ID"));
     Bitmap bitmap = MediaStore.Images.Thumbnails.getThumbnail(cr,
       thumbNailsId, Video.Thumbnails.MICRO_KIND, null);
     //若為視頻則為
//     Bitmap bitmap = MediaStore.Video.Thumbnails.getThumbnail(cr,
//       thumbNailsId, Video.Thumbnails.MICRO_KIND, null);
     return bitmap;
    }