分页组件

"""
自定义分页组件
以后如果想要使用这个分页组件，需要做：

在视图函数中：
    from app01.utils.pagination import Pagination
    def prettynum_list(request):

        #1.根据自己的情况去筛选自己的数据
        queryset = models.PrettyNum.objects.all()

        #2.实例化分页对象
        page_object = Pagination(request, queryset)

        context = {
            "search_data": search_data,

            'queryset': page_object.page_queryset, #分完页的数据
            "page_string": page_object.html()      #生成的页码
        }

        #返回到前端页面
        return render(request, 'prettynum_list.html', context)

在HTML页面中：

    {% for obj in queryset %}
            <th>{{ obj.xx }}</th>
            <td>{{ obj.xxx}}</td>
    {% endfor %}

    <ul class="pagination" >
        {{ page_string }}
    </ul>
"""
from django.utils.safestring import mark_safe
import copy

class Pagination(object):

    def __init__(self, request, queryset, page_size = 10, page_param="page", plus = 5):
        """
        :param request:请求的对象
        :param queryset:符合条件的数据(根据此数据进行分页处理)
        :param page_size:每页显示多少条数据
        :param page_param:获取在URL中传递的分页参数, 例如: /pretty/list/?page=21
        :param plus:页码显示当前页的前几页后几页
        """
        # 防止搜索出结果进行翻页时,URL参数没有了搜索参数
        query_dict = copy.deepcopy(request.GET)
        query_dict._mutable = True
        self.query_dict = query_dict

        self.page_param = page_param

        page = int(request.GET.get(page_param, 1))
        # 如果不是整数
        if type(page) != int:
            # 强制让页码为1
            page = 1
        # if page.isdecimal():
        #     page = int(page)
        # else:
        #     page = 1
        self.page = page

        self.page_size = page_size

        self.start = (page - 1) * page_size
        self.end = page * page_size

        # 每页展示的数据行数
        self.page_queryset = queryset[self.start:self.end]

        # 获取到符合条件的数据的总条数
        total_count = queryset.count()
        total_page_count, div = divmod(total_count, page_size)
        if div:
            total_page_count += 1
        self.total_page_count = total_page_count
        self.plus = plus

    def html(self):

        # 计算出显示当前页的前5页、后5页
        if self.total_page_count <= 2 * self.plus + 1:
            # 数据库中的数据比较少，都没有达到11项
            start_page = 1
            end_page = self.total_page_count
        else:
            # 数据库中的数据比较多 大于11项

            # 当前页小于5时, （小极值）
            if self.page <= self.plus:
                start_page = 1
                end_page = 2 * self.plus + 1
            else:
                # 当前页>5
                # 当前页+5>总页面
                if (self.page + self.plus) > self.total_page_count:
                    start_page = self.total_page_count - 2 * self.plus
                    end_page = self.total_page_count
                else:
                    start_page = self.page - self.plus
                    end_page = self.page + self.plus

        # 页码
        page_str_list = []

        self.query_dict.setlist(self.page_param, [1])
        # 首页
        page_str_list.append('<li><a href="?{}">首页</a></li>'.format(self.query_dict.urlencode()))

        # 上一页
        if self.page > 1:
            self.query_dict.setlist(self.page_param, [self.page - 1])
            prev = '<li><a href="?{}">上一页</a></li>'.format(self.query_dict.urlencode())
        else:
            self.query_dict.setlist(self.page_param, [1])
            prev = '<li><a href="?{}">上一页</a></li>'.format(self.query_dict.urlencode())
        page_str_list.append(prev)

        # 页面
        # range前取后不取，所以total_page_count+1
        for i in range(start_page, end_page + 1):
            self.query_dict.setlist(self.page_param, [i])
            # 给当前页加一个样式
            if i == self.page:
                ele = '<li class="active"><a href="?{}">{}</a></li>'.format(self.query_dict.urlencode(), i)
            else:
                ele = '<li><a href="?{}">{}</a></li>'.format(self.query_dict.urlencode(), i)
            page_str_list.append(ele)

        # 下一页
        if self.page < self.total_page_count:
            self.query_dict.setlist(self.page_param, [self.page + 1])
            prev = '<li><a href="?{}">下一页</a></li>'.format(self.query_dict.urlencode())
        else:
            self.query_dict.setlist(self.page_param, [self.total_page_count])
            prev = '<li><a href="?{}">下一页</a></li>'.format(self.query_dict.urlencode())
        page_str_list.append(prev)

        # 尾页
        self.query_dict.setlist(self.page_param, [self.total_page_count])
        page_str_list.append('<li><a href="?{}">尾页</a></li>'.format(self.query_dict.urlencode()))

        search_string = """
        <li>
            <form style="float: left; margin-left: -1px" method="get">
                <input type="text" name="page"
                       style="position: relative; float: left; display: inline-block; width: 80px; border-radius: 0;"
                       class="form-control" placeholder="页码">
                <button style="border-radius: 0" class="btn btn-default" type="submit">跳转</button>
            </form>
        </li>
        """
        page_str_list.append(search_string)
        page_string = mark_safe("".join(page_str_list))
        return page_string