/**
     * Get an array with file names of all category images in drawable folder.
     *
     * @return the file names of all catergories in drawable folder.
     */
    public String[] getCategoryDrawables() {
        Field[] fields = R.drawable.class.getFields();
        String[] categoryDrawables = new String[fields.length];

        // Place all category images in the array.
        for (int i = 0; i < categoryDrawables.length; i++) {

            // Iterate through NoteCategories and get the drawables that matches
            // the category names.
            for (NoteCategory category : NoteCategory.values()) {
                if (category.toString().equals(categoryDrawables[i])) {
                    categoryDrawables[i] = fields[i].getName();
                }
            }
        }

        return categoryDrawables;
    }