Django pagination page_obj.number is not changing

Question

I have following view and the content is rendered correctly. The pagination is also correct. The only issue is that the page_obj.number in the template is always 1. Even clicking on page 3 the content of page 3 is shown but the page_obj.number is still 1. Maybe I'm doing something wrong in my view. Here the view:

class SpecificationListView(AjaxRequiredMixin, ListView):
    model = Category
    context_object_name = 'categories'
    template_name = 'catalog/specification/listSpecificationFiltered.html'
    paginate_by = 2

    def get_queryset(self):
        search_value = self.request.POST.get('searchValue', None)
        sel_category = self.request.POST.get('selCategory', 'ALL')
        chk_active = self.request.POST.get('chkActive', 0)

        category_filters = Q()
        if sel_category != 'ALL':
            category_filters = category_filters & Q(pk=sel_category)

        specification_filters = Q()
        search_value = None if (search_value == '' or len(search_value) < 3) else search_value
        if search_value is not None:
            specification_filters = specification_filters & Q(name__icontains=search_value)
        if chk_active == '1':
            specification_filters = specification_filters & Q(is_active=True)

        # categories are retrieved to build the tree in template
        categories_list = Category.objects.distinct().filter(category_filters)
        category_ids = categories_list.values_list('id', flat=True)  # category ids on page
        specification_filters = specification_filters & Q(category_id__in=category_ids)
        categories_list = categories_list.prefetch_related(
            Prefetch(
                'specifications',
                queryset=Specification.objects.filter(specification_filters)
            )
        )

        return categories_list

    def post(self, request, *args, **kwargs):
        return self.get(request, *args, **kwargs)

    def get_context_data(self, **kwargs):
        context = super(SpecificationListView, self).get_context_data(**kwargs)

        page = self.request.POST.get('page')
        paginator = Paginator(self.object_list, self.paginate_by)
        categories = paginator.get_page(int(page))

        context.update({
            'categories': categories,
            'page_title': _('Manage Specifications'),
            'actions_allowed': self.request.user.is_allowed('Specification.Manage'),
        })
        return context

In my template I use a templatetag to render the pagination like:

{% if is_paginated %}
    {{ page_obj|render_paginator }}
{% endif %}

The templatetag looks like this:

@register.filter(name='render_paginator')
def paginate_(page_obj):
    html = '<div class="d-flex justify-content-between align-items-center flex-wrap">'
    html += '<div class="d-flex flex-wrap py-2 mr-3">'

    previous_page = (page_obj.number - 1) if (page_obj.number - 1) > 0 else 1
    last_page = len(page_obj.paginator.page_range)
    next_page = (page_obj.number + 1) if (page_obj.number + 1) <= last_page else last_page

    disabled = ''
    if page_obj.number == 1:
        disabled = ' disabled'
    html += '<a href="?page=1" class="btn btn-icon btn-sm btn-light mr-2 my-1{}"><i class="ki ki-bold-double-arrow-back icon-xs"></i></a>'.format(disabled)
    html += '<a href="?page={}" class="btn btn-icon btn-sm btn-light mr-2 my-1{}"><i class="ki ki-bold-arrow-back icon-xs"></i></a>'.format(page_obj.previous_page_number, disabled)

    for nb in page_obj.paginator.page_range:
        active = ''
        if page_obj.number == nb:
            active = 'btn-hover-primary active'
        html += '<a href="?page={}" class="btn btn-icon btn-sm border-0 btn-light {} mr-2 my-1">{}</a>'.format(nb, active, nb)

    disabled = ' disabled'
    if page_obj.has_next:
        disabled = ''
    html += '<a href="?page={}" class="btn btn-icon btn-sm btn-light mr-2 my-1{}"><i class="ki ki-bold-arrow-next icon-xs"></i></a>'.format(page_obj.next_page_number, disabled)
    html += '<a href="?page={}" class="btn btn-icon btn-sm btn-light mr-2 my-1{}"><i class="ki ki-bold-double-arrow-next icon-xs"></i></a>'.format(page_obj.paginator.num_pages, disabled)
    html += '</div>'

    html += '<div class="d-flex align-items-center py-3">'
    html += '<select id="selLimit" class="form-control form-control-sm font-weight-bold mr-4 border-0 bg-light" style="width: 75px;">'
    for i in range(5, 50, 5):
        html += '<option value="{}">{}</option>'.format(i, i)
    html += '</select>'

    html += '</div>'
    html += '</div>'

    return mark_safe(html)

Thank you in advance for any help

Answer 1

I found the answer: As categories are paged, I have to pass the categories to the templatetag, like:

{% if is_paginated %}
    {{ categories|render_paginator }}
{% endif %}