我正在使用django，但我的静态文件未加载

Question

这些是我的文件，请告诉我我做错了什么或需要进行哪些更改

settings.py

STATIC_URL = '/static/'
STATIC_ROOT = os.path.join(BASE_DIR, 'assets')
STATICFILES_DIRS = (
    os.path.join(BASE_DIR, 'static'),
)
STATICFILES_FINDERS = (
    'django.contrib.staticfiles.finders.FileSystemFinder',
    'django.contrib.staticfiles.finders.AppDirectoriesFinder',
)

index.html

{% load static %}
<link rel="stylesheet" type="text/css" href="{% static 
'firstapp/style.css' %}"/>
    <h1>Here are all Albums</h1>
    {% if all_albums %}

        <ul>
            {% for album in all_albums %}
            <li><a href="{% url 'firstapp:detail' album.id %}">{{ album.album_title }}</a> </li>
            {% endfor %}
        </ul>
    {% else %}
        <h1>No data found</h1>
    {% endif %}

style.css

body{
    background: white url{"images/background.png"};
}

mysite / firstapp / urls.py

app_name = 'firstapp'

urlpatterns = [
    url(r'^$', views.index, name='index'),
    url(r'^(?P<album_id>[0-9]+)/$',views.detail, name='detail'),
    url(r'^(?P<album_id>[0-9]+)/favorite/$', views.favorite, name='favorite'),
]

mysite / mysite / urls.py

urlpatterns = [
    url('admin/', admin.site.urls),
    url(r'^firstapp/', include('firstapp.urls')),
]

This is the file structure