WEB框架之Django实现分页功能

一 Paginator分页器

1 首先在数据库中生成大量数据

def index(request)
    book_list = []
    for i in rang(1000)
        book = Book(title="book_%s" %i, price=i*i)
        book_list.append(book)
    Book.objects.bulk_create(book_list)          # 批量插入数据

2 分页器中的主要方法

from django.core.paginator import Paginator

paginator = Paginator(book_list,8)             # 每页展示几条内容
print("count:",paginator.count)                # 总页数
print("page_range",paginator.page_range)       # 页码的列表
print("num_pages",paginator.num_pages)         # 总页数
page1 = paginator.page(1)                      # 第1页的page对象
for i in page1                                 # 遍历第1页的所有数据对象
    print(i)
                
page2 = paginator.page(2)
print(page2.hax_next())                        # 是否有下一页
print(page2.next_page_number())                # 下一页页码
print(page2.has_pervious())                    # 是否有上一页
print(page2.pervious_page_number())            # 上一页的页码

3 实现页面分页

模板：

{% if current_page.has_previous %}                          先判断是否有上一页，如果没有就把'上一页'关闭
     <li>
          <a href="?page={{ current_page_num|add:-1 }}" aria-label="Previous">
          <span aria-hidden="true">&laquo;</span>
          </a>
      </li>
{% else %}
      <li class="disabled">
           <a href="" aria-label="Previous">
           <span aria-hidden="true">&laquo;</span>
           </a>
     </li>
{% endif %}

{% for item in page_range %}

        {% if current_page_num == item %}
                <li class="active"><a  href="?page={{ item }}">{{ item }}</a></li>
        {% else %}
                <li><a  href="?page={{ item }}">{{ item }}</a></li>
        {% endif %}
{% endfor %}

{% if current_page.has_next %}
        <li>
           <a href="?page={{ current_page_num|add:1 }}" aria-label="Next">
           <span aria-hidden="true" class="put-right">&raquo;</span>
           </a>
        </li>
{% endif %}

视图函数：

book_list = Book.objects.all()　　　　          # 获取全部数据
paginator = Paginator(book_list, 10)　　　　　　 # 每页显示10条内容
current_page_num = int(request.GET.get("page", 1))   # 当前在哪一页

if paginator.num_pages > 11:
       if current_page_num -5<1:
             page_range = range(1,11)
      elif current_page_num +5>paginator.num_pages:
             page_range=range(paginator.num_pages-11, paginator.num _pages+1)
      else:
             page_range = range(current_page_num-5, current_page_num+6)
else:
       page_range = paginator.page_range

print("count:", paginator.count)
print("num_pages:", paginator.num_pages)
print("page_range:", page_range)
for i in  page_range:
     print(i)
try:
      current_page = paginator.page(current_page_num)   # 第一页的数据对象
      print("object_list", current_page.object_list)
except:
      current_page = paginator.page(1)
return render(request, 'index.html',locals())

二 自定义分页

1 直接在函数中实现分页

def get_data(req):
   if req.metho == 'GET':
        current_page = request.GET.get('page',1)    # 获取用户传来的请求页面(相当于当前页面)，默认是1
        current_page = int(current_page)  
        # 制造切片
        start = (current_page - 1) * 10
        end = current_page * 10    
        data = models.User.objects.all()[start:end]         # 一次取10条数据
        # 总个数
        total_count = models.Classes.objects.all().count()
        # 用总个数和每页显示的个数相处，求商和余数，如果有余数总页码还需+1
        v,a = divmod(total_count,10)  # 相当于总页数 
        if a != 0:
            v+=1   
       # 生成页码
       page_list = []
       # 如果是第一页那么上一页的功能就取消
       if current_page == 1:
           page_list.append('<a href="#">上一页</a>' %(current_page-1)
       else:
           page_list.append('<a href="/index?page=%s">上一页</a>' %(current_page-1)  
        # 判断并生成page_range
       if v <= 11:
            pager_range_start =1
            ager_range_end = v
       else:
           if current_page <6:
              pager_range_start = 1
              pager_range_end = 11 +1
           else:
              pager_range_start = current_page -5
              pager_range_end = current_page +6
              if pager_range_end > v:
                  page_range_start = current_page - 10
                  pager_range_end = v +1
                              
        for i in range(pager_range_star,pager_range_end)
              if i == current_page:
                  page_list.append('<a href="/index?page=%s" class=actice>%s</a>' %(i,i))
              page_list.append('<a href="/index?page=%s">%s</a>' %(i,i))
            
        # 如果当前页是最后一页那么下一页功能就取消
         if current_page == v:
             page_list.append('<a href="#">下一页</a>' %(current_page+1)
        else：
            page_list.append('<a href="/index?page=%s">下一页</a>' %(current_page+1)
            
         pager = "".join(pager_list)
         return render(request,{'data':data,'str_page':pager})

2 将自定义的分页器封装成一个类

class PagerHandler：
            def __inin__(self,total_count,current_page, base_url. per_page=10):
                self.total_count = total_count
                self.current_page = current_page
                self.base_url = base_url
                self.per_page = per_page
                
            def db_start(self):
                return (self.current_page -1) * self.per_page
                
            def db_end(self):
                return (self.current_page) * self.per_page
            
            def tootal_page(self):
                v,a = divmod(total_count,10)  # 相当于总页数 
                if a != 0:
                    v+=1
                return v

            def pager_str(self):
                
                v = self.tootal_page()
                # 生成页码
                page_list = []
                # 如果是第一页那么上一页的功能就取消
                if self.current_page == 1:
                    page_list.append('<a href="#">上一页</a>' %(self.current_page-1)
                else:
                    page_list.append('<a href="/%s?page=%s">上一页</a>' %(self.base_url,self.current_page-1)
                
                # 判断并生成page_range
                if v <= 11:
                    pager_range_start =1
                    pager_range_end = v
                else:
                    if current_page <6:
                        pager_range_start = 1
                        pager_range_end = 11 +1
                    else:
                        pager_range_start = self.current_page -5
                        pager_range_end = self.current_page +6
                        if pager_range_end > v:
                            page_range_start = self.current_page - 10
                            pager_range_end = v +1

                for i in range(pager_range_star,pager_range_end)
                    if i == self.current_page:
                        page_list.append('<a href="/%s?page=%s" class=actice>%s</a>' %(self.base_url,i,i))
                    page_list.append('<a href="/%s?page=%s">%s</a>' %(self.base_url,i,i))
                
                # 如果当前页是最后一页那么下一页功能就取消
                if self.current_page == v:
                    page_list.append('<a href="#">下一页</a>' %(self.current_page+1)
                else：
                    page_list.append('<a href="/%s?page=%s">下一页</a>' %(self.base_url,self.current_page+1)
                pager = "".join(pager_list)
                return pager

3 在视图函数中调用

def index(request)
    if request.method == 'GET':
        current_page = request.GET.get('page',1)
        current_page = int(current_page)
        # 数据总数
        total_count = models.Classes.objects.all().count()
        page_obj = PagerHandler(total_count,current_page,'/index/')
        pager = page_obj.pager_str()    
        data = models.Classes.objects.all()[page_obj.db_start():page_obj.db_end()]
　　　　 return render(request,'index.html',{'data':data,'pager':pager})

 4 也页面中保留过滤条件班分页组件

class Pagination:
    def __init__(self, data_num, current_page, params,  url_prefix,  per_page=10, max_show=11):
        """
        进行初始化.
        :param data_num: 数据总数
        :param current_page: 当前页
        :param url_prefix: 生成的页码的链接前缀
        :param per_page: 每页显示多少条数据
        :param max_show: 页面最多显示多少个页码
        """

        self.data_num = data_num
        self.per_page = per_page
        self.max_show = max_show
        self.url_prefix = url_prefix

        # 把页码数算出来
        self.page_num, more = divmod(data_num, per_page)
        if more:
            self.page_num += 1

        try:
            self.current_page = int(current_page)
        except Exception as e:
            self.current_page = 1
            # 如果URL传过来的页码数是负数
        if self.current_page <= 0:
            self.current_page = 1
            # 如果URL传过来的页码数超过了最大页码数
        elif self.current_page > self.page_num:
            self.current_page = self.page_num  # 默认展示最后一页

        # 页码数的一半 算出来
        self.half_show = self.max_show // 2
        # 如果数据总页码self.page_num<11 pager_page_count
        if self.page_num <= self.max_show:
            self.page_start = 1
            self.page_end = self.page_num
        else:
            # 数据页码已经超过11
            # 判断： 如果当前页 <= 5 self.half_show
            if self.current_page <= self.half_show:
                self.page_start = 1
                self.page_end = self.max_show
            else:
                # 如果： 当前页+5 > 总页码
                if (self.current_page + self.half_show) > self.page_num:
                    self.page_start = self.page_num - self.max_show + 1
                    self.page_end = self.page_num
                else:
                    self.page_start = self.current_page - self.half_show
                    self.page_end = self.current_page + self.half_show

        import copy
        self.params = params # {"page":"12","title_startwith":"py","id__gt":"5"}

    @property
    def start(self):
        # 数据从哪儿开始切
        return (self.current_page - 1) * self.per_page

    @property
    def end(self):
        # 数据切片切到哪儿
        return self.current_page * self.per_page

    def page_html(self):
        # 生成页码
        l = []
        # 加一个首页
        first_page = self.params
        first_page['page'] = 1
        l.append('<li><a href="{}?{}">首页</a></li>'.format(self.url_prefix, first_page.urlencode()))
        # 加一个上一页
        if self.current_page == 1:
            l.append('<li class="disabled" ><a href="#">«</a></li>'.format(self.current_page))
        else:
            self.params['page'] = self.current_page - 1
            l.append('<li><a href="{}?{}">«</a></li>'.format(self.url_prefix, self.params.urlencode()))

        for i in range(self.page_start, self.page_end + 1):
            self.params['page'] = i
            if i == self.current_page:
                tmp = '<li class="active"><a href="{}?{}">{}</a></li>'.format(self.url_prefix, self.params.urlencode(), i)
            else:
                tmp = '<li><a href="{}?{}">{}</a></li>'.format(self.url_prefix, self.params.urlencode(), i)
            l.append(tmp)

        # 加一个下一页
        if self.current_page == self.page_num:
            l.append('<li class="disabled"><a href="#">»</a></li>'.format(self.current_page))
        else:
            self.params['page'] = self.current_page + 1
            l.append('<li><a href="{}?{}">»</a></li>'.format(self.url_prefix, self.params.urlencode()))
        # 加一个尾页
        last_page = self.params
        last_page['page'] = self.page_num
        l.append('<li><a href="{}?{}">尾页</a></li>'.format(self.url_prefix, last_page.urlencode()))
        return "".join(l)