Android : how to be sure that image is ready to use

i want to create a thumbnail after i took a picture but sometimes the image isn't finished yet and then i get a nullpointer exception

    @Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
    if (requestCode == REQUEST_IMAGE_CAPTURE && resultCode == RESULT_OK) {
        //Bitmap bitmp = (Bitmap) data.getExtras().get("data");
        BitmapFactory.Options bmpFactoryOptions = new BitmapFactory.Options();
        bmpFactoryOptions.inJustDecodeBounds = false;

        sendBroadcast(new Intent(Intent.ACTION_MEDIA_MOUNTED, Uri.parse("file://" + Environment.getExternalStorageDirectory())));

        // Bitmap btmp = Bitmap.createScaledBitmap(bmp, bmp.getWidth()/12, bmp.getHeight()/12, true);

        Bitmap bmp = BitmapFactory.decodeFile(imageFilePath, bmpFactoryOptions);

        CommentDialog(bmp);
    }

}

is there a way to check if image finished?