Refreshing the thumbnail using MediaScanner

问题

When I save an image to new location and then use MediaScanner to refresh the gallery then everything is fine - thumbnails and images are refreshed well.

But when I save an image to EXISTING location and then use MediaScanner - then only 'new' thumbnail isnt refreshed. (even though file is overwritten).

How to solve it?

Here is my code :

File file = new File(SDCARD_PATH, filename);

try {
    FileOutputStream out = new FileOutputStream(file);
    bmp.compress(format, BEST_IMAGE_QUALITY, out);
}catch (FileNotFoundException e) {

}

//refreshing single file using media scanner, no need to paste

回答1:

This is a common and well know problem in Android. If you edit a media file, the thumbnail does not seem to update.

I have a fix for this, however, its still a fix and not a clean solution. My fix is simple, and it basically deletes the stale thumbnail and then uses media scanner to update the thumbnails.

Here're the steps to be followed:

Step 1. Edit the file as you like. Say filename, "myVideoToBeEdited".

Step 2. Once you are done editing, delete its existing thumbnail. First, get the video id using code like this:

                final String[] columns = {
                    BaseColumns._ID, MediaColumns.DATA
                };

            ContentResolver cr = context.getContentResolver();
            Cursor cursor = cr.query(MediaStore.Video.Media.EXTERNAL_CONTENT_URI, columns, null, null, null);

            boolean cancel = false;
            if(null != cursor){
                while(cursor.moveToNext() && !cancel){
                    String fileName = cursor.getString(cursor.getColumnIndex(MediaColumns.DATA));
                    int imageId = cursor.getInt(cursor.getColumnIndex(BaseColumns._ID));

                    if(fileName.equals(myVideoToBeEdited)){
                        removeVideoThumbnail(getContentResolver(), imageId); // step 3
                        cancel = true;
                    }
                }
            }

There are other ways to get the id, and more optimised ones as well.

Step 3. Delete the thumbnail.

        public void removeVideoThumbnail(ContentResolver contentResolver, long photoId) {
        Cursor thumbnails = contentResolver.query(android.provider.MediaStore.Video.Thumbnails.EXTERNAL_CONTENT_URI, null, android.provider.MediaStore.Video.Thumbnails.VIDEO_ID + "=?", new String[]{String.valueOf(photoId)}, null);
        for (thumbnails.moveToFirst(); !thumbnails.isAfterLast(); thumbnails.moveToNext()) {

            long thumbnailId = thumbnails.getLong(thumbnails.getColumnIndex(android.provider.MediaStore.Video.Thumbnails._ID));
            String path = thumbnails.getString(thumbnails.getColumnIndex(android.provider.MediaStore.Video.Thumbnails.DATA));
            File file = new File(path);
            if (file.delete()) {

                contentResolver.delete(android.provider.MediaStore.Video.Thumbnails.EXTERNAL_CONTENT_URI, android.provider.MediaStore.Video.Thumbnails._ID + "=?", new String[]{String.valueOf(thumbnailId)});

            }

        }
    }

Or, here's the method to delete image thumbnail

    public void removeImageThumbnail(ContentResolver contentResolver, long photoId) {
        Cursor thumbnails = contentResolver.query(android.provider.MediaStore.Images.Thumbnails.EXTERNAL_CONTENT_URI, null, android.provider.MediaStore.Images.Thumbnails.IMAGE_ID + "=?", new String[]{String.valueOf(photoId)}, null);
        for (thumbnails.moveToFirst(); !thumbnails.isAfterLast(); thumbnails.moveToNext()) {

            long thumbnailId = thumbnails.getLong(thumbnails.getColumnIndex(android.provider.MediaStore.Images.Thumbnails._ID));
            String path = thumbnails.getString(thumbnails.getColumnIndex(android.provider.MediaStore.Images.Thumbnails.DATA));
            File file = new File(path);
            if (file.delete()) {

                contentResolver.delete(android.provider.MediaStore.Images.Thumbnails.EXTERNAL_CONTENT_URI, android.provider.MediaStore.Images.Thumbnails._ID + "=?", new String[]{String.valueOf(thumbnailId)});

            }

        }
    }

Step 4. And finally use media scanner connection to scan the file so that it updates the thumbnails.

         MediaScannerConnection.scanFile(context,
              new String[] { myVideoToBeEdited }, null,
              new MediaScannerConnection.OnScanCompletedListener() {
          public void onScanCompleted(String path, Uri uri) {
                      // pass the mime type, else passing a null will enable file extension to dictate the mime type
              // you are good to go
          }
     });

回答2:

Have you tried to remove the "old" picture prior to saving the new one to file system? Like so:

File file = new File(SDCARD_PATH, filename);

try {
    // Delete the "old" file.
    if (file.exists()) {
        file.delete();
    }

    FileOutputStream out = new FileOutputStream(file);
    bmp.compress(format, BEST_IMAGE_QUALITY, out);
}catch (FileNotFoundException e) {
}catch (SecurityException e) {
}

来源：https://stackoverflow.com/questions/7805527/refreshing-the-thumbnail-using-mediascanner