一、自定義分頁遵守的

• 當前頁，當前頁可能會被傳入特別的值建議異常就是第一頁

• 底欄展示頁碼

• 數據總個數用來計算生成多少頁

• 每頁展示頁數

邏輯

• 首先我們利用切片，把數據分成段落顯示，每一頁的第一條數據是（當前頁-1）*頁面顯示條數

 @property
    def start(self):
        '''
        :return: 開始頁數
        '''
        return (self.current_page-1)*self.page_count

• 每頁最后一條數據是（當前頁*顯示條數）

 @property
    def end(self):
        '''
        :return: 結束頁數
        '''
        return (self.current_page*self.page_count)

• 頁面的總頁數是總條數/頁面顯示頁數

 @property
    def total_count(self):
        '''
        :return: 總頁數
        '''
        v, y = divmod(self.data_count,self.page_count)
        if y:
            v +=1
        return v

• 頁面展示的條數也就是循環次數

• 當總頁數小于頁面實際展示頁數時，開始頁1，結束頁實際頁數
• 當總頁數大于頁面實際展示頁數時
• 第一種情況當前頁小于中間頁，開始頁1，結束頁是頁面展示底欄
• 第二種情況當前頁大于中間頁，開始頁當前頁-（中間頁-1）/2，結束頁（當前頁+1）/2
• 當然第二種的前提建立在（當前頁+（中間頁-1）/2）大于總頁數
  開始頁總頁數-底欄數-1，結束頁等于總頁數+1

_author__ = 'Administrator'
from django.utils.safestring import mark_safe


class Pagination(object):
    def __init__(self, current_page, data_count, per_page_count=1, pager_num=7):
        try:
            self.current_page = int(current_page)
        except Exception as e:
            self.current_page = 1
        self.data_count = data_count
        self.per_page_count = per_page_count
        self.pager_num = pager_num

    @property
    def start(self):
        return (self.current_page - 1) * self.per_page_count

    @property
    def end(self):
        return self.current_page * self.per_page_count

    @property
    def total_count(self):
        v, y = divmod(self.data_count, self.per_page_count)
        if y:
            v += 1
        return v

    def page_str(self, base_url):
        page_list = []

        if self.total_count < self.pager_num:
            start_index = 1
            end_index = self.total_count + 1
        else:
            if self.current_page <= (self.pager_num + 1) / 2:
                start_index = 1
                end_index = self.pager_num + 1
            else:
                start_index = self.current_page - (self.pager_num - 1) / 2
                end_index = self.current_page + (self.pager_num + 1) / 2
                if (self.current_page + (self.pager_num - 1) / 2) > self.total_count:
                    end_index = self.total_count + 1
                    start_index = self.total_count - self.pager_num + 1

        if self.current_page == 1:
            prev = '<li><a class="page" href="javascript:void(0);">上一頁</a></li>'
        else:
            prev = '<li><a class="page" href="%s?p=%s">上一頁</a></li>' % (base_url, self.current_page - 1,)
        page_list.append(prev)

        for i in range(int(start_index), int(end_index)):
            if i == self.current_page:
                temp = '<li class="active"><a class="page active" href="%s?p=%s">%s</a></li>' % (base_url, i, i)
            else:
                temp = '<li><a class="page" href="%s?p=%s">%s</a></li>' % (base_url, i, i)
            page_list.append(temp)

        if self.current_page == self.total_count:
            nex = '<li><a class="page" href="javascript:void(0);">下一頁</a></li>'
        else:
            nex = '<li><a class="page" href="%s?p=%s">下一頁</a></li>' % (base_url, self.current_page + 1,)
        page_list.append(nex)

        # jump = """
        # <input type='text'  /><a onclick='jumpTo(this, "%s?p=");'>GO</a>
        # <script>
        #     function jumpTo(ths,base){
        #         var val = ths.previousSibling.value;
        #         location.href = base + val;
        #     }
        # </script>
        # """ % (base_url,)
        #
        # page_list.append(jump)

        page_str = mark_safe("".join(page_list))

        return page_str