<!DOCTYPE html>
<head>
<meta http-equiv="Content-Type" content="text/htmlcharset=utf-8" />
<title>jQuery分页演示效果</title>
<script type="text/javascript" src="/img/jquery1.3.2.js"></script>
<script type="text/javascript">
$(document).ready(function(){
var show_per_page = 5
var number_of_items = $('#content').children().size()
var number_of_pages = Math.ceil(number_of_items/show_per_page)
$('#current_page').val(0)
$('#show_per_page').val(show_per_page)
var navigation_html = '<a class="previous_link" href="javascript:previous()">Prev</a>'
var current_link = 0
while(number_of_pages >current_link){
navigation_html += '<a class="page_link" href="javascript:go_to_page(' + current_link +')" longdesc="' + current_link +'">'+ (current_link + 1) +'</a>'
current_link++
}
navigation_html += '<a class="next_link" href="javascript:next()">Next</a>'
$('#page_navigation').html(navigation_html)
$('#page_navigation .page_link:first').addClass('active_page')
$('#content').children().css('display', 'none')
$('#content').children().slice(0, show_per_page).css('display', 'block')
})
function previous(){
new_page = parseInt($('#current_page').val()) - 1
if($('.active_page').prev('.page_link').length==true){
go_to_page(new_page)
}
}
function next(){
new_page = parseInt($('#current_page').val()) + 1
//if there is an item after the current active link run the function
if($('.active_page').next('.page_link').length==true){
go_to_page(new_page)
}
}
function go_to_page(page_num){
var show_per_page = parseInt($('#show_per_page').val())
start_from = page_num * show_per_page
end_on = start_from + show_per_page
$('#content').children().css('display', 'none').slice(start_from, end_on).css('display', 'block')
$('.page_link[longdesc=' + page_num +']').addClass('active_page').siblings('.active_page').removeClass('active_page')
$('#current_page').val(page_num)
}
</script>
<style>
#page_navigation a{
padding:3px
border:1px solid gray
margin:2px
color:black
text-decoration:none
}
.active_page{
background:darkblue
color:white !important
}
</style>
</head>
<body>
<input type='hidden' id='current_page' />
<input type='hidden' id='show_per_page' />
<div id='content'>
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</div>
<div id='page_navigation'></div><br>
<br>
</body>
</html>
ViewHolder通常出现在适配器里，为的是listview滚动的时候快速设置值，而不必每次都重新创建很多对象，从而提升性能。在android开发中Listview是一个很重要的组件，它以列表的形式根据数据的长自适应展示具体内容,用户可以自由的定义listview每一列的布局，但当listview有大量的数据需要加载的时候，会占据大量内存，影响性能，这时候就需要按需填充并重新使用view来减少对象的创建。
ListView加载数据都是在public View getView(int position, View convertView,
ViewGroup parent)
{}方法中进行的(要自定义listview都需要重写listadapter:如BaseAdapter，SimpleAdapter,CursorAdapter的等的getvView方法),优化listview的加载速度就要让convertView匹配列表类型，并最大程度上的重新使用convertView。
getview的加载方法一般有以下三种种方式：
最慢的加载方式是每一次都重新定义一个View载入布局，再加载数据
public View getView(int position, View convertView, ViewGroup parent)
{
View item = mInflater.inflate(R.layout.list_item_icon_text,
null)
((TextView)
item.findViewById(R.id.text)).setText(DATA[position])
((ImageView) item.findViewById(R.id.icon)).setImageBitmap(
(position &1) == 1 ? mIcon1 : mIcon2)
return item
}
正确的加载方式是当convertView不为空的时候直接重新使用convertView从而减少了很多不必要的View的创建，然后加载数据
public View getView(int position, View convertView, ViewGroup parent)
{
if (convertView == null) {
convertView = mInflater.inflate(R.layout.item, parent, false)
}
((TextView)
convertView.findViewById(R.id.text)).setText(DATA[position])
((ImageView)
convertView.findViewById(R.id.icon)).setImageBitmap(
(position &1) == 1 ? mIcon1 : mIcon2)
return convertView
}
最快的方式是定义一个ViewHolder，将convetView的tag设置为ViewHolder,不为空时重新使用即可
static class ViewHolder {
TextView text
ImageView icon
}
public View getView(int position, View convertView, ViewGroup parent)
{
ViewHolder holder
if (convertView == null) {
convertView = mInflater.inflate(R.layout.list_item_icon_text,
parent, false)
holder = new ViewHolder()
holder.text = (TextView) convertView.findViewById(R.id.text)
holder.icon = (ImageView) convertView.findViewById(R.id.icon)
convertView.setTag(holder)
} else {
holder = (ViewHolder) convertView.getTag()
}
holder.text.setText(DATA[position])
holder.icon.setImageBitmap((position &1) == 1 ? mIcon1 :
mIcon2)
return convertView
}
参考：http://blog.csdn.net/jacman/article/details/7087995
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