How to add Media Provider?

Question

When I download an image and save it to the Android device the image does not appear in the gallery, later after the phone is restarted the images are in the gallery.

Here is the code where I download the images and save them to the device:

 private void downloadImage() {
    if (future != null) {
        //set the callback and start downloading
        future.withResponse().setCallback(new FutureCallback<Response<InputStream>>() {
            @Override
            public void onCompleted(Exception e, Response<InputStream> result) {
                boolean success = false;
                if (e == null && result != null && result.getResult() != null) {
                    try {
                        //prepare the file name
                        String url = mSelectedImage.getUrl();
                        String fileName = url.substring(url.lastIndexOf('/') + 1, url.length());
                        //create a temporary directory within the cache folder
                        File dir = Utils.getAlbumStorageDir("wall-tx");
                        //create the file
                        File file = new File(dir, fileName);
                        if (!file.exists()) {
                            file.createNewFile();
                        }

                        //copy the image onto this file
                        Utils.copyInputStreamToFile(result.getResult(), file);

                        //animate the first elements
                        animateCompleteFirst(true);

                        success = true;
                    } catch (Exception ex) {
                        Log.e("walltx", ex.toString());
                    }

                    //animate after complete
                    animateComplete(success);
                } else {
                    animateReset(true);
                }
            }
        });
    }
}

Utils.java

/**
 * http://stackoverflow.com/questions/326390/how-to-create-a-java-string-from-the-contents-of-a-file
 *
 * @param file
 * @return
 * @throws IOException
 */
public static String readFile(File file)
        throws IOException {
    return new Scanner(file, "UTF-8").useDelimiter("\\A").next();
}

/**
 * http://developer.android.com/training/basics/data-storage/files.html
 *
 * @param albumName
 * @return
 */

public static File getAlbumStorageDir(String albumName) {
    // Get the directory for the user's public pictures directory.
    boolean success = false;
    File file = new File(Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_PICTURES), albumName);
    if (!file.exists()) {
        success = file.mkdir();
    }
    if (!success)
        Log.i("wall-tx", "Directory not created");
    else
        Log.i("wall-tx", "Directory created");
    return file;
}
/**
 * http://developer.android.com/training/basics/data-storage/files.html
 *
 * @return
 */
public static boolean isExternalStorageWritable() {
    String state = Environment.getExternalStorageState();
    if (Environment.MEDIA_MOUNTED.equals(state)) {
        return true;
    }
    return false;
}