django分页器

目录

• 一、分页器思路
• 二、自定义分页器的使用

一、分页器思路

分页器主要听处理逻辑 代码最后很简单 
推导流程
	1.queryset支持切片操作(正数)
	2.研究各个参数之间的数学关系
 		每页固定展示多少条数据、起始位置、终止位置
 	3.自定义页码参数
    	current_page = request.GET.get('page')
 	4.前端展示分页器样式
	5.总页码数问题
    	divmod方法
 	6.前端页面页码个数渲染问题
    	后端产生 前端渲染(通常来说后端返回的都是奇数的页码个数)

部分代码展示

def ab_bk_func(request):
    per_page_num = 10  # 每页展示多少条数据
    current_page = request.GET.get('page', 1)
    try:
        current_page = int(current_page)
    except BaseException:
        current_page = 1
    book_queryset = models.Books01.objects.all()
    all_count = book_queryset.count()

    all_page_num, more = divmod(all_count, per_page_num)
    if more:
        all_page_num += 1
    # 由于模板语法没有range功能 但是我们需要循环产生很多分页标签 所以考虑后端生成传递给html页面
    html_str = ''
    xxx = current_page
    if xxx < 6:
        xxx = 6
    for i in range(xxx - 5, xxx + 6):
        if current_page == i:
            html_str += '<li class="active"><a href="?page=%s">%s</a></li>' % (i, i)
        else:
            html_str += '<li><a href="?page=%s">%s</a></li>' % (i, i)

    start_num = (current_page - 1) * per_page_num  # 起始展示位置
    end_num = current_page * per_page_num  # 终止展示位置
    book_queryset = book_queryset[start_num:end_num]
    return render(request, 'BkPage.html', locals())


"""
per_page_num=10   all_count=100   page_num=10
per_page_num=10   all_count=101   page_num=11
per_page_num=10   all_count=99   page_num=10
我们想通过代码动态计算出总共需要多少页

"""
"""
per_page_num = 10
current_page                start_num                   end_num 
    1                       0                           10
    2                       10                          20
    3                       20                          30


per_page_num = 5
current_page                start_num                   end_num 
    1                       0                           5
    2                       5                           10
    3                       10                          15
    
start_num = (current_page - 1) * per_page_num
end_num = current_page * per_page_num
"""

二、自定义分页器的使用

django自带分页器模块但是使用起来很麻烦 所以我们自己封装了一个（只需要掌握使用方式即可，以后用的不多）

步骤一：在应用目录下创建一个文件夹，比如utils文件夹，并在该目录下创建一个py文件（如mypage.py）

步骤二：复制自定义分页器的代码到我们创建的py文件中

class Pagination(object):
    def __init__(self, current_page, all_count, per_page_num=2, pager_count=11):
        """
        封装分页相关数据
        :param current_page: 当前页
        :param all_count:    数据库中的数据总条数
        :param per_page_num: 每页显示的数据条数
        :param pager_count:  最多显示的页码个数
        """
        try:
            current_page = int(current_page)
        except Exception as e:
            current_page = 1
 
        if current_page < 1:
            current_page = 1
 
        self.current_page = current_page
 
        self.all_count = all_count
        self.per_page_num = per_page_num
 
        # 总页码
        all_pager, tmp = divmod(all_count, per_page_num)
        if tmp:
            all_pager += 1
        self.all_pager = all_pager
 
        self.pager_count = pager_count
        self.pager_count_half = int((pager_count - 1) / 2)
 
    @property
    def start(self):
        return (self.current_page - 1) * self.per_page_num
 
    @property
    def end(self):
        return self.current_page * self.per_page_num
 
    def page_html(self):
        # 如果总页码 < 11个：
        if self.all_pager <= self.pager_count:
            pager_start = 1
            pager_end = self.all_pager + 1
        # 总页码  > 11
        else:
            # 当前页如果<=页面上最多显示11/2个页码
            if self.current_page <= self.pager_count_half:
                pager_start = 1
                pager_end = self.pager_count + 1
 
            # 当前页大于5
            else:
                # 页码翻到最后
                if (self.current_page + self.pager_count_half) > self.all_pager:
                    pager_end = self.all_pager + 1
                    pager_start = self.all_pager - self.pager_count + 1
                else:
                    pager_start = self.current_page - self.pager_count_half
                    pager_end = self.current_page + self.pager_count_half + 1
 
        page_html_list = []
        # 添加前面的nav和ul标签
        page_html_list.append('''
                    <nav aria-label='Page navigation>'
                    <ul class='pagination'>
                ''')
        first_page = '<li><a href="?page=%s">首页</a></li>' % (1)
        page_html_list.append(first_page)
 
        if self.current_page <= 1:
            prev_page = '<li class="disabled"><a href="#">上一页</a></li>'
        else:
            prev_page = '<li><a href="?page=%s">上一页</a></li>' % (self.current_page - 1,)
 
        page_html_list.append(prev_page)
 
        for i in range(pager_start, pager_end):
            if i == self.current_page:
                temp = '<li class="active"><a href="?page=%s">%s</a></li>' % (i, i,)
            else:
                temp = '<li><a href="?page=%s">%s</a></li>' % (i, i,)
            page_html_list.append(temp)
 
        if self.current_page >= self.all_pager:
            next_page = '<li class="disabled"><a href="#">下一页</a></li>'
        else:
            next_page = '<li><a href="?page=%s">下一页</a></li>' % (self.current_page + 1,)
        page_html_list.append(next_page)
 
        last_page = '<li><a href="?page=%s">尾页</a></li>' % (self.all_pager,)
        page_html_list.append(last_page)
        # 尾部添加标签
        page_html_list.append('''
                                           </nav>
                                           </ul>
                                       ''')
        return ''.join(page_html_list)

步骤三：自定义分页器的使用

后端代码

每个变量名的含义可以参考源码的注释

    封装分页相关数据

    :param current_page: 当前页

    :param all_count:    数据库中的数据总条数

    :param per_page_num: 每页显示的数据条数

    :param pager_count:  最多显示的页码个数

 def get_book(request):
   book_list = models.Book.objects.all()
   current_page = request.GET.get("page",1)
   all_count = book_list.count()
   page_obj = Pagination(current_page=current_page,all_count=all_count,per_page_num=10)
   page_queryset = book_list[page_obj.start:page_obj.end]
   return render(request,'booklist.html',locals())

前端代码

ps：需要有bootstrap样式

<div class="container">
    <div class="row">
        <div class="col-md-8 col-md-offset-2">
            {% for book in page_queryset %}
            <p>{{ book.title }}</p>
            {% endfor %}
            {{ page_obj.page_html|safe }}
        </div>
    </div>
</div>