Django学习（5）优雅地分页展示网页

       在我们平时浏览网页时，经常会遇到网页里条目很多的情形，这时就会用到分页展示的功能。那么，在Django中，是如何实现网页分类的功能的呢？答案是Paginator类。

       本次分享讲具体展示如何利用Django的Paginator类来实现网页的分页展示功能。

       首先我们要展示的内容是159首陶渊明的诗歌，它们储存在'/home/vagrant/poem.txt'文件中。

       默认的不分页的网页（page.html）如下：

         其模板的代码如下：

<ul>
{% for contact in contacts %}
<li>{{contact}}<br><br></li>
{% endfor %}
</ul>

<div>
<center>
{% if contacts.has_previous %}  
<a href="?page={{ contacts.previous_page_number }}"> 上一页</a>  
{% endif %}  
<span>  
    {% for p in contacts.paginator.page_range %}  
    {% ifequal p contacts.number %}  
    <span class="current">{{p}}</span>  
    {% else %}  
    <a href="?page={{p}}" title="第{{p}}页"><button>{{p}}</button></a>  
    {% endifequal %}
    {% endfor %}  
</span>  
{% if contacts.has_next %}  
<a href="?page={{ contacts.next_page_number }}">下一页 > </a>  
{% endif %}  
<a>[page:{{ contacts.number }}/{{ contacts.paginator.num_pages }}]</a>
</center> 
</div> 

<br>
<form action="/fenye/" method="get">
    <center>
    <select name='items'>
        <option value='10' checked="checked">10 items each page</option>
        <option value='15'>15  items each page</option>
        <option value='20'>20  items each page</option>
    </select>
    <input type="submit" value="select">
    </center>     
</form>

该网页中的数字按钮可连接到对应的页码，当然也可以用‘下一页’链接。也可以自由选择每页需要显示的条目数量，如下：

选择好条目数，在点击select按钮，可链接到如下页面：

           这个页面（fenye.html）显示每页10条，可以点击按钮‘Return To Original Page’回到刚才的页面（page.html）。该页面（fenye.html）的模板代码如下：

<ul>
{% for contact in contacts %}
<li>{{contact}}<br><br></li>
{% endfor %}
</ul>

<div>
<center>
{% if contacts.has_previous %}  
<a href="?page={{ contacts.previous_page_number }}"> 上一页</a>  
{% endif %}  
<span>  
    {% for p in contacts.paginator.page_range %}  
    {% ifequal p contacts.number %}  
    <span class="current">{{p}}</span>  
    {% else %}  
    <a href="?page={{p}}" title="第{{p}}页"><button>{{p}}</button></a>  
    {% endifequal %}
    {% endfor %}  
</span>  
{% if contacts.has_next %}  
<a href="?page={{ contacts.next_page_number }}">下一页 > </a>  
{% endif %}  
<a>[page:{{ contacts.number }}/{{ contacts.paginator.num_pages }}]</a>
</center> 
</div> 
<center>
    <br>
    <button onclick="window.location.href='http://localhost:8000/page'">Return To Original Page</button>
</center>

           最后，我们的后端views.py代码如下：

from django.http import HttpResponse
from django.shortcuts import render_to_response
from django.utils.datastructures import MultiValueDictKeyError
from django.core.paginator import Paginator,PageNotAnInteger,EmptyPage

#show items in default 
def output(request):
    # get items show on the page from poems.txt
    with open('/home/vagrant/poems.txt', 'r') as f:
        text = f.readlines()
        
    items_each_page = 15  # how many items in each page
    paginator = Paginator(text, items_each_page)
    page = request.GET.get('page')  # get 'page'
    try:
        contacts = paginator.page(page)
    except PageNotAnInteger:
        # If page is not an integer, deliver first page.
        contacts = paginator.page(1)
    except EmptyPage:
        # If page is out of range (e.g. 9999), deliver last page of results.
        contacts = paginator.page(paginator.num_pages)
    return render_to_response('page.html',{'contacts': contacts})

#show items by your choice
def output2(request):
    with open('/home/vagrant/poems.txt', 'r') as f:
        text = f.readlines()
        
    try:
        #try to get 'items', if None or failed, do nothing.
        a = request.GET.get('items')
        if str(a) != 'None':
            with open('/home/vagrant/num.txt', 'w') as f:
                f.write(a)
    except:
        pass

    with open('/home/vagrant/num.txt','r') as f:
        items_each_page = int(f.read())

    paginator = Paginator(text, items_each_page)
    page = request.GET.get('page')
    try:
        contacts = paginator.page(page)
    except PageNotAnInteger:
        # If page is not an integer, deliver first page.
        contacts = paginator.page(1)
    except EmptyPage:
        # If page is out of range (e.g. 9999), deliver last page of results.
        contacts = paginator.page(paginator.num_pages)    
    return render_to_response('fenye.html',{'contacts': contacts})

       这样，我们就基本实现了在Django中网页分页展示的功能，而且能够自己选择每一页需要展示的条目的数量，这显然是非常方便使用的。

       本次分享到此结束，如有问题，欢迎大家交流与批评~~