zoukankan html css js c++ java

分页器组件

准备

models.py

from django.db import models

class Author(models.Model):
    name = models.CharField(max_length=32)
    books = models.ManyToManyField(to="Book")

    def __str__(self):
        return self.name

    class Meta:
        db_table = "author"

class Book(models.Model):
    title = models.CharField(max_length=32)

    def __str__(self):
        return self.title

    class Meta:
        db_table = "book"

urls.py

from app01 import views

urlpatterns = [
    url(r'^admin/', admin.site.urls),
    url(r'^books/$', views.books),
]

books.html

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>书籍列表</title>
    <link rel="stylesheet" href="/static/bootstrap/css/bootstrap.min.css">
</head>
<body>
    <div class="container">
        <table class="table table-bordered">
            <thead>
                <tr>
                    <th>序号</th>
                    <th>id</th>
                    <th>书名</th>
                </tr>
            </thead>
            <tbody>
            {% for book in books %}
                <tr>
                    <td>{{ forloop.counter }}</td>
                    <td>{{ book.id }}</td>
                    <td>{{ book.title }}</td>
                </tr>
            {% endfor %}

            </tbody>
        </table>
    </div>
</body>
</html>

批量插入数据

import os
import sys

if __name__ == "__main__":
    os.environ.setdefault("DJANGO_SETTINGS_MODULE", "page_demo.settings")

    import django
    django.setup()

    from app01 import models
    # 批量创建
    # 有100个书籍对象
    objs = [models.Book(title="书本{}".format(i)) for i in range(100)]

    # 在数据库中批量创建, 10次一提交
    models.Book.objects.bulk_create(objs, 10)

展示所有的数据

from django.shortcuts import render
from app01 import models

def books(request):
    all_book = models.Book.objects.all()
    return render(request, "books.html", {"books": all_book})

需求

现在需求是做一个类似博客园的分页

当点击第一页的时候，URL 显示为 /books/?page=1/ ，并显示第一页的数据，一页展示 10 条数据

展示

规律

可以在视图函数里使用切片操作，当要展示第一页的数据，即 1-10 条数据，它的索引是 [0:10]

from django.shortcuts import render
from app01 import models

def books(request):
    all_book = models.Book.objects.all()[:10]
    return render(request, "books.html", {"books": all_book})

展示第一页的数据，即 11-20 条数据，它的索引是 [10:20]

from django.shortcuts import render
from app01 import models

def books(request):
    all_book = models.Book.objects.all()[10:20]
    return render(request, "books.html", {"books": all_book})

所以，它的规律是：

from django.shortcuts import render
from app01 import models

def books(request):
    # 从URL取参数
    page_num = request.GET.get("page")
    page_num = int(page_num)

    # 定义两个变量保存数据从哪取到哪
    data_start = (page_num-1) * 10
    data_end = page_num * 10

    all_book = models.Book.objects.all()[data_start: data_end]
    return render(request, "books.html", {"books": all_book})

增加样式

增加 bootstrap 样式，显示可点击跳转的页码。首先要算出总页码数

可以根据 divmod() 计算，当有 20 条数据，每页展示 10 条，计算出 (2, 0) ，当有 21 条数据，计算出 (2, 1) ，计算出的值里右边的为 0，左边的就是页码数，否则左边的页码数就加一。

然后自己拼接一个 a 标签，将拼接好的传入模板

from django.shortcuts import render
from app01 import models

def books(request):
    # 从URL取参数
    page_num = request.GET.get("page")
    page_num = int(page_num)

    # 定义两个变量保存数据从哪取到哪
    data_start = (page_num - 1) * 10
    data_end = page_num * 10

    # 每一页显示多少条数据
    per_page = 10

    # 总数据是多少
    total_count = models.Book.objects.all().count()
    # 总共需要多少页码来展示
    total_page, m = divmod(total_count, per_page)
    if m:
        total_page += 1

    all_book = models.Book.objects.all()[data_start: data_end]

    # 拼接分页的html代码
    html_str_list = []
    for i in range(1, total_page + 1):
        tmp = '<li><a href="/books/?page={0}">{0}</a></li>'.format(i)
        html_str_list.append(tmp)

    page_html = "".join(html_str_list)

    return render(request, "books.html", {"books": all_book, "page_html": page_html})

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>书籍列表</title>
    <link rel="stylesheet" href="/static/bootstrap/css/bootstrap.min.css">
</head>
<body>
<div class="container">
    <table class="table table-bordered">
        <thead>
        <tr>
            <th>序号</th>
            <th>id</th>
            <th>书名</th>
        </tr>
        </thead>
        <tbody>
        {% for book in books %}
            <tr>
                <td>{{ forloop.counter }}</td>
                <td>{{ book.id }}</td>
                <td>{{ book.title }}</td>
            </tr>
        {% endfor %}

        </tbody>
    </table>
    <nav aria-label="Page navigation">
        <ul class="pagination">
            <li>
                <a href="#" aria-label="Previous">
                    <span aria-hidden="true">&laquo;</span>
                </a>
            </li>
            {{ page_html | safe }}
            <li>
                <a href="#" aria-label="Next">
                    <span aria-hidden="true">&raquo;</span>
                </a>
            </li>
        </ul>
    </nav>
</div>
</body>
</html>

添加多条数据

以上便是一个简单分页的实现，这是数据比较少的情况，现在向数据库添加至 1000 条数据，再进行页面展示

这显然是不合理的，博客园中页码中间是用省略号，省略号前面的页码一般都为奇数，且始终只有 200 页

所以这里的需求是，展示的页码数固定为 11 页，当前所在页码的前后页码数对称。假如当前在第六页，前面展示五个，后面也展示五个，也就是 1-11 页

有了展示的开始页码和结束页码，拼接 html 代码时也要有所改动

多条数据的首尾页码

然后考虑首尾的问题，如果当前页减一半比 1 小，还是需要固定 1-11 页

如果当前页比 100 大，后面不再显示页码

这时，当处于第一页时，上一页不可点击，同样，处于最后一页时，下一页也不可点击。看起来实现了分页的操作，但此时删除至只有一条数据，又出现了页码为负数的情况。

所以要有一个判断

# 页面上总共展示多少页码
max_page = 11
# 当总页码数小于展示的页码数
if total_page < max_page:
    max_page = total_page

这样，便能够访问了，再做一些完善，比如用户输入页码数不是数字，或者大于最大的页码数，让当前页码加一个 active 类等。

最终代码

from django.shortcuts import render
from app01 import models


# Create your views here.

def books(request):
    # 从URL取参数
    page_num = request.GET.get("page")

    # 每一页显示多少条数据
    per_page = 10

    # 总数据是多少
    total_count = models.Book.objects.all().count()
    # 总共需要多少页码来展示
    total_page, m = divmod(total_count, per_page)
    if m:
        total_page += 1

    try:
        page_num = int(page_num)
        # 如果输入的页码超过了最大的页码数，默认返回最后一页
        if page_num > total_page:
            page_num = total_page
    except Exception as e:
        # 当输入的页码不是数字的时候，默认返回第一页的数据
        page_num = 1

    # 定义两个变量保存数据从哪取到哪
    data_start = (page_num - 1) * 10
    data_end = page_num * 10

    # 页面上总共展示多少页码
    max_page = 11
    if total_page < max_page:
        max_page = total_page

    half_max_page = max_page // 2
    # 页面上展示的页码从哪开始
    page_start = page_num - half_max_page
    # 页面上展示的页码到哪结束
    page_end = page_num + half_max_page

    # 如果当前页减一半 比1小
    if page_start <= 1:
        page_start = 1
        page_end = max_page

    # 如果当前页加一半 比总页码数还大
    if page_end >= total_page:
        page_end = total_page
        page_start = total_page - max_page + 1

    all_book = models.Book.objects.all()[data_start: data_end]

    # 拼接分页的html代码
    html_str_list = []
    # 加上第一页
    html_str_list.append('<li><a href="/books/?page=1">首页</a></li>')

    # 加上一页，上一页就是当前页减一
    # 判断，如果第一页，就没有上一页
    if page_num <= 1:
        html_str_list.append('<li class="disabled"><a href="#"><span aria-hidden="true">&laquo;</span></a></li>')
    else:
        html_str_list.append(
            '<li><a href="/books/?page={}"><span aria-hidden="true">&laquo;</span></a></li>'.format(page_num - 1))

    for i in range(page_start, page_end + 1):
        # 如果是当前页，加一个active样式类
        if i == page_num:
            tmp = '<li class="active"><a href="/books/?page={0}">{0}</a></li>'.format(i)
        else:
            tmp = '<li><a href="/books/?page={0}">{0}</a></li>'.format(i)
        html_str_list.append(tmp)

    # 加下一页，下一页就是当前页加一
    # 判断，如果是最后一页，就没有下一页
    if page_num >= total_page:
        html_str_list.append('<li class="disabled"><a href="#"><span aria-hidden="true">&raquo;</span></a></li>')
    else:
        html_str_list.append(
            '<li><a href="/books/?page={}"><span aria-hidden="true">&raquo;</span></a></li>'.format(page_num + 1))

    # 加最后一页
    html_str_list.append('<li><a href="/books/?page={}">尾页</a></li>'.format(total_page))

    page_html = "".join(html_str_list)

    return render(request, "books.html", {"books": all_book, "page_html": page_html})

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>书籍列表</title>
    <link rel="stylesheet" href="/static/bootstrap/css/bootstrap.min.css">
</head>
<body>
<div class="container">
    <table class="table table-bordered">
        <thead>
        <tr>
            <th>序号</th>
            <th>id</th>
            <th>书名</th>
        </tr>
        </thead>
        <tbody>
        {% for book in books %}
            <tr>
                <td>{{ forloop.counter }}</td>
                <td>{{ book.id }}</td>
                <td>{{ book.title }}</td>
            </tr>
        {% endfor %}

        </tbody>
    </table>
    <nav aria-label="Page navigation">
        <ul class="pagination">
            {{ page_html | safe }}
        </ul>
    </nav>
</div>
</body>
</html>

封装成通用的模块

class Page():
    def __init__(self, page_num, total_count, url_prefix, per_page=10, max_page=11):
        """
        :param page_num: 当前页码数
        :param total_count: 数据总数
        :param url_prefix: a标签href的前缀
        :param per_page: 每页显示多少条数据
        :param max_page: 页面上最多显示几个页码
        """
        self.url_prefix = url_prefix
        self.max_page = max_page

        # 每一页显示多少条数据
        # 总共需要多少页码来展示
        total_page, m = divmod(total_count, per_page)
        if m:
            total_page += 1
        self.total_page = total_page

        try:
            page_num = int(page_num)
            # 如果输入的页码超过了最大的页码数，默认返回最后一页
            if page_num > total_page:
                page_num = total_page
        except Exception as e:
            # 当输入的页码不是数字的时候，默认返回第一页的数据
            page_num = 1
        self.page_num = page_num

        # 定义两个变量保存数据从哪取到哪
        self.data_start = (page_num - 1) * 10
        self.data_end = page_num * 10

        # 页面上总共展示多少页码
        if total_page < self.max_page:
            self.max_page = total_page

        half_max_page = self.max_page // 2
        # 页面上展示的页码从哪开始
        page_start = page_num - half_max_page
        # 页面上展示的页码到哪结束
        page_end = page_num + half_max_page

        # 如果当前页减一半 比1小
        if page_start <= 1:
            page_start = 1
            page_end = self.max_page

        # 如果当前页加一半 比总页码数还大
        if page_end >= total_page:
            page_end = total_page
            page_start = total_page - self.max_page + 1
        self.page_start = page_start
        self.page_end = page_end

    @property
    def start(self):
        return self.data_start

    @property
    def end(self):
        return self.data_end

    def page_html(self):
        # 拼接分页的html代码
        html_str_list = []
        # 加上第一页
        html_str_list.append('<li><a href="{}?page=1">首页</a></li>'.format(self.url_prefix))

        # 加上一页，上一页就是当前页减一
        # 判断，如果第一页，就没有上一页
        if self.page_num <= 1:
            html_str_list.append('<li class="disabled"><a href="#"><span aria-hidden="true">&laquo;</span></a></li>')
        else:
            html_str_list.append(
                '<li><a href="{}?page={}"><span aria-hidden="true">&laquo;</span></a></li>'.format(self.url_prefix,
                                                                                                   self.page_num - 1))

        for i in range(self.page_start, self.page_end + 1):
            # 如果是当前页，加一个active样式类
            if i == self.page_num:
                tmp = '<li class="active"><a href="{0}?page={1}">{1}</a></li>'.format(self.url_prefix, i)
            else:
                tmp = '<li><a href="{0}?page={1}">{1}</a></li>'.format(self.url_prefix, i)
            html_str_list.append(tmp)

        # 加下一页，下一页就是当前页加一
        # 判断，如果是最后一页，就没有下一页
        if self.page_num >= self.total_page:
            html_str_list.append('<li class="disabled"><a href="#"><span aria-hidden="true">&raquo;</span></a></li>')
        else:
            html_str_list.append(
                '<li><a href="{}?page={}"><span aria-hidden="true">&raquo;</span></a></li>'.format(self.url_prefix,
                                                                                                   self.page_num + 1))

        # 加最后一页
        html_str_list.append('<li><a href="{}?page={}">尾页</a></li>'.format(self.url_prefix, self.total_page))

        page_html = "".join(html_str_list)
        return page_html

from django.shortcuts import render

# Create your views here.
from app01 import models

def books(request):
    # 从URL取参数
    page_num = request.GET.get("page")

    # 调用一个类
    from utils.mypage import Page
    page_obj = Page(page_num, total_count, per_page=10, url_prefix="/books/", max_page=11)
    ret = models.Book.objects.all()[page_obj.start: page_obj.end]
    page_html = page_obj.page_html()
    return render(request, "books.html", {"books": ret, "page_html": page_html})

def depts(request):
    # 从URL中取参数
    page_num = request.GET.get("page")
    # 总数据是多少
    total_count = models.Dept.objects.all().count()
    from utils.mypage import Page
    page_obj = Page(page_num, total_count, per_page=10, url_prefix="/depts/", max_page=11)
    ret = models.Dept.objects.all()[page_obj.start: page_obj.end]
    page_html = page_obj.page_html()
    return render(request, "dept.html", {"depts": ret, "page_html": page_html})

完整代码：https://github.com/qiuxirufeng/page_demo

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原文地址：https://www.cnblogs.com/qiuxirufeng/p/11620097.html