本期解读源码：
django.contrib.admin下ModelAdmin类中方法changelist_view
def changelist_view(self, request, extra_context=None):
"""
The 'change list' admin view for this model.
changelist_view管理视图函数主要用于django自带后台admin管理模型时，用户初始看到的模型信息显示列表
视图函数一共有三个参数
self：代表ModelAdmin类本身
request：代表这次请求
extra_context：代表额外的信息，这里extra_context默认为None，说明在访问这个方法时，即便是没带上extra_context也能正常访问
"""
# 从django.contrib.admin.views.main导入错误报警ERROR_FLAG
from django.contrib.admin.views.main import ERROR_FLAG
# opts为当前管理模型的Meta属性，可理解为当前管理模型的别名
opts = self.model._meta
# 当前管理模型的app标签，这个在app.py和init.py中设置
app_label = opts.app_label
# 判断当前请求用户有没有查看或者修改权限，没有抛出异常PermissionDenied
if not self.has_view_or_change_permission(request):
raise PermissionDenied
try:
#尝试得到请求数据列表的实例
cl = self.get_changelist_instance(request)
# 如果不能正常得到，捕获异常IncorrectLookupParameters
except IncorrectLookupParameters:
# Wacky lookup parameters were given, so redirect to the main
# changelist page, without parameters, and pass an 'invalid=1'
# parameter via the query string. If wacky parameters were given
# and the 'invalid=1' parameter was already in the query string,
# something is screwed up with the database, so display an error
# page.
# 异常显示页面
if ERROR_FLAG in request.GET:
return SimpleTemplateResponse('admin/invalid_setup.html', {
'title': _('Database error'),
})
return HttpResponseRedirect(request.path + '?' + ERROR_FLAG + '=1')
# If the request was POSTed, this might be a bulk action or a bulk
# edit. Try to look up an action or confirmation first, but if this
# isn't an action the POST will fall through to the bulk edit check,
# below.
# 默认action按钮是未被点击的
action_failed = False
# 得到被选择的项目的列表
selected = request.POST.getlist(helpers.ACTION_CHECKBOX_NAME)
# 得到请求的action
actions = self.get_actions(request)
# Actions with no confirmation
if (actions and request.method == 'POST' and
'index' in request.POST and '_save' not in request.POST):
if selected:
response = self.response_action(request, queryset=cl.get_queryset(request))
if response:
return response
else:
action_failed = True
else:
msg = _("Items must be selected in order to perform "
"actions on them. No items have been changed.")
self.message_user(request, msg, messages.WARNING)
action_failed = True
# Actions with confirmation
if (actions and request.method == 'POST' and
helpers.ACTION_CHECKBOX_NAME in request.POST and
'index' not in request.POST and '_save' not in request.POST):
if selected:
response = self.response_action(request, queryset=cl.get_queryset(request))
if response:
return response
else:
action_failed = True
if action_failed:
# Redirect back to the changelist page to avoid resubmitting the
# form if the user refreshes the browser or uses the "No, take
# me back" button on the action confirmation page.
return HttpResponseRedirect(request.get_full_path())
# If we're allowing changelist editing, we need to construct a formset
# for the changelist given all the fields to be edited. Then we'll
# use the formset to validate/process POSTed data.
formset = cl.formset = None
# Handle POSTed bulk-edit data.
if request.method == 'POST' and cl.list_editable and '_save' in request.POST:
if not self.has_change_permission(request):
raise PermissionDenied
FormSet = self.get_changelist_formset(request)
modified_objects = self._get_list_editable_queryset(request, FormSet.get_default_prefix())
formset = cl.formset = FormSet(request.POST, request.FILES, queryset=modified_objects)
if formset.is_valid():
changecount = 0
for form in formset.forms:
if form.has_changed():
obj = self.save_form(request, form, change=True)
self.save_model(request, obj, form, change=True)
self.save_related(request, form, formsets=[], change=True)
change_msg = self.construct_change_message(request, form, None)
self.log_change(request, obj, change_msg)
changecount += 1
if changecount:
msg = ngettext(
"%(count)s %(name)s was changed successfully.",
"%(count)s %(name)s were changed successfully.",
changecount
) % {
'count': changecount,
'name': model_ngettext(opts, changecount),
}
self.message_user(request, msg, messages.SUCCESS)
return HttpResponseRedirect(request.get_full_path())
# Handle GET -- construct a formset for display.
elif cl.list_editable and self.has_change_permission(request):
FormSet = self.get_changelist_formset(request)
formset = cl.formset = FormSet(queryset=cl.result_list)
# Build the list of media to be used by the formset.
if formset:
media = self.media + formset.media
else:
media = self.media
# Build the action form and populate it with available actions.
if actions:
action_form = self.action_form(auto_id=None)
action_form.fields['action'].choices = self.get_action_choices(request)
media += action_form.media
else:
action_form = None
selection_note_all = ngettext(
'%(total_count)s selected',
'All %(total_count)s selected',
cl.result_count
)
context = {
**self.admin_site.each_context(request),
'module_name': str(opts.verbose_name_plural),
'selection_note': _('0 of %(cnt)s selected') % {'cnt': len(cl.result_list)},
'selection_note_all': selection_note_all % {'total_count': cl.result_count},
'title': cl.title,
'is_popup': cl.is_popup,
'to_field': cl.to_field,
'cl': cl,
'media': media,
'has_add_permission': self.has_add_permission(request),
'opts': cl.opts,
'action_form': action_form,
'actions_on_top': self.actions_on_top,
'actions_on_bottom': self.actions_on_bottom,
'actions_selection_counter': self.actions_selection_counter,
'preserved_filters': self.get_preserved_filters(request),
**(extra_context or {}),
}
request.current_app = self.admin_site.name
return TemplateResponse(request, self.change_list_template or [
'admin/%s/%s/change_list.html' % (app_label, opts.model_name),
'admin/%s/change_list.html' % app_label,
'admin/change_list.html'
], context)