需求描述：

使用django寫了一個投票後臺，如果想給每個問題加一個圖片的話就需要用到MEDIA_URL，MEDIA_ROOT等等了。

整個過程需要用到[app名]下的models.py,[app名]下的urls.py,[app名]下的settings.py，出發！！

目前[app名]下的models.py的代碼如下：

from django.db import models
from django.utils import timezone
import datetime


# Create your models here.
class Question(models.Model):
    question_text = models.CharField(max_length=220)
    pub_date = models.DateTimeField("date published")

    def __str__(self):
        return self.question_text

    def was_published_recently(self):
        now = timezone.now()
        return now - datetime.timedelta(days=1) <= self.pub_date <= now

    was_published_recently.admin_order_field = "pub_date"
    was_published_recently.boolean = True
    was_published_recently.short_description = '是否最近發佈'

class Choice(models.Model):
    question = models.ForeignKey(Question, on_delete=models.CASCADE)
    choice_text = models.CharField(max_length=220)
    count = models.IntegerField(default=0)

    def __str__(self):
        return self.choice_text

[app名]下的urls.py的代碼如下：

from django.contrib import admin
from django.urls import path, include
from mysite import settings
urlpatterns = [
    path('polls/', include("polls.urls")),
    path('admin/', admin.site.urls),

]

因爲settings中的內容過長，並且我們不需要進行修改，只是添加，所以就不將settings.py的代碼貼上了。

實現

首先打開[app名]下的settings.py：
- 添加兩個字段，分別爲【MEDIA_ROOT】，【MEDIA_URL】

# 設置上傳的文件的存放路徑
MEDIA_ROOT = os.path.join(BASE_DIR, "media")
# 設置直接訪問上傳文件的url（訪問路徑）
MEDIA_URL = "/media/"

其次打開[app名]下的urls.py：
- 添加如下代碼，設置路由
```
urlpatterns += static(settings.MEDIA_URL, document_root=settings.MEDIA_ROOT)
```
  按住ctrl點擊static進入類中，執行return中內容設置路由

最後打開[app名]下的models.py：

在Question類中添加如下代碼：

avatar = models.FileField(upload_to='polls/')

完整models.py代碼如下：

from django.db import models
from django.utils import timezone
import datetime


# Create your models here.
class Question(models.Model):
    question_text = models.CharField(max_length=220)
    pub_date = models.DateTimeField("date published")
    avatar = models.FileField(upload_to='polls/')

    def __str__(self):
        return self.question_text

    def was_published_recently(self):
        now = timezone.now()
        return now - datetime.timedelta(days=1) <= self.pub_date <= now

    was_published_recently.admin_order_field = "pub_date"
    was_published_recently.boolean = True
    was_published_recently.short_description = '是否最近發佈'

class Choice(models.Model):
    question = models.ForeignKey(Question, on_delete=models.CASCADE)
    choice_text = models.CharField(max_length=220)
    count = models.IntegerField(default=0)

    def __str__(self):
        return self.choice_text

最最後，執行【python manage.py makemigrations】和【python manage.py migrate】兩條命令，進行表結構更改，遷移。
重啓服務器後登陸admin，選擇Question，選擇ADD QUESTION，選擇必須的信息和圖片後，保存成功，可以在後臺看到添加的圖片了，也通過MEDIA_URL加路徑訪問已經上傳的圖片