position | 易学教程

图片比例自适应居中与CSS垂直水平居中

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图片比例自适应居中说明最近项目里有这样一个需求：要求是在图片外部的框框是大小一致、图片的长宽比不一致，且图片能够在固定高度的情况下，使得图片的宽度能保持原有的比例，及宽度不压缩，图片始终在外部div的最中间，如下图所示图片宽度大于外部边框的情况下，两边会有一部分看不见原图效果图图片宽度小于外部边框的情况下，两边会留白原图效果图代码在网上找了许多资料，最终使用了下面的方案，效果很OK html部分 < div class = "img" > < img src = "xxx.jpg" > </ div > css部分 .img { width : 100 % ; height : 255 px ; overflow : hidden ; position : relative ; border-radius : 4 px 4 px 0 0 ; } img { height : 100 % ; width : auto ; position : absolute ; top : 0 ; left : 50 % ; transform : translateX(- 50 %) ; } CSS垂直水平居中说明垂直水平居中，即要求一段文字或图片或其他在外部div容器中垂直水平居中放置，如下图所示效果图代码依然是用 transform 的思想

背景图自适应屏幕居中显示，且不变形

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html： <div class='item'> <div class = 'container' /> </div> css: .item { width: 100% ; height: 100% ; .container { max -width: 100% ; height: auto; min -height: 600px; // 这里可监听屏幕变化，改变最小高度 position: absolute; left: 50% ; top: 50% ; transform: translate( -50%, -50%); // 利用位移实现居中 background-image: url(./img/1 .png); background -size: 100% ; background -repeat: no- repeat; background -position: center 0 ; 　　　　　} } 转载于:https://www.cnblogs.com/aloehui/p/10238299.html 来源： CSDN 作者： weixin_34049032 链接： https://blog.csdn.net/weixin_34049032/article/details/93737553

How do I get a vertical scroll bar on an inner div contained in a fixed dimension outer div?

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问题 I'm looking for an HTML/CSS solution where an inner DIV has the following characteristics: MUST HAVE: is included within a fixed height container div below a variable height sibling header div. fills available variable height with no max-height CSS property scrolls vertically if necessary to accommodate content is within a document having DOCTYPE = HTML 4.01 strict (preferably, HTML 5 if necessary) is multi-browser compatible (Chrome, Firefox, IE, Safari, mobile-phone browsers) WOULD LIKE TO

Explain详解与索引最佳实践

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使用EXPLAIN关键字可以模拟优化器执行SQL语句，从而知道MySQL是如何处理你的SQL语句的。分析你的查询语句或是结构的性能瓶颈下面是使用 explain 的例子：在 select 语句之前增加 explain 关键字，MySQL 会在查询上设置一个标记，执行查询时，会返回执行计划的信息，而不是执行这条SQL（如果 from 中包含子查询，仍会执行该子查询，将结果放入临时表中）使用的表 DROP TABLE IF EXISTS `actor`; CREATE TABLE `actor` ( `id` int(11) NOT NULL, `name` varchar(45) DEFAULT NULL, `update_time` datetime DEFAULT NULL, PRIMARY KEY (`id`) ) ENGINE=InnoDB DEFAULT CHARSET=utf8; INSERT INTO `actor` (`id`, `name`, `update_time`) VALUES (1,'a','2017-12-22 15:27:18'), (2,'b','2017-12-22 15:27:18'), (3,'c','2017-12-22 15:27:18'); DROP TABLE IF EXISTS `film`; CREATE TABLE

Iphone 802.11 Scan

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问题 I'm developing a system of indoor position use wifi. however I am having problems with relation to this library of apple. was once private is now public. where I use the code. libHandle = dlopen(”/System/Library/SystemConfiguration/IPConfiguration.bundle/IPConfiguration”, RTLD_LAZY); apple80211Open = dlsym(libHandle, “Apple80211Open”); apple80211Bind = dlsym(libHandle, “Apple80211BindToInterface”); apple80211Close = dlsym(libHandle, “Apple80211Close”); apple80211Scan = dlsym(libHandle,

原生JS经典射击游戏-小蜜蜂

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经典射击游戏-小蜜蜂做之前的大概思路看下面这个图，这个游戏我打算用单例模式来写也就是平常我们说的单体模式。源码链接在线玩经典射击游戏-小蜜蜂单体是一个用来划分命名空间并将一批相关的属性和方法组织在一起的对象，如果他可以被实例化，那么他只能被实例化一次。单体模式是javascript里面最基本但是也是最有用的也是最常用的模式之一。单体模式的特点：可以用来划分命名空间，从而清除全局变量所带来的危险,也就是该类只有一个实例该类自行创建该实例，即在该类内部创建自身的实例对象，向整个系统公开这个实例接口。利用分支技术来封装浏览器直接的差异可以把代码组织的更为一体，便于阅读和维护。单体模式的思路是：一个类能返回一个对象的引用（并且永远是同一个）和一个获得该实例的方法（静态方法，通常使用getInstance名称）。那么当我们调用这个方法时，如果类持有的引用不为空就返回该引用，否者就创建该类的实例，并且将实例引用赋值给该类保持的那个引用再返回。同时将该类的构造函数定义为私有方法，避免其他函数使用该构造函数来实例化对象，只通过该类的静态方法来得到该类的唯一实例。用一句话来说，单例模式的核心是确保只有一个实例，并提供全局访问。布局代码 <!doctype html> < html lang = "en" > < head > < meta charset = "UTF-8"

数据结构,约瑟夫环非链表解...

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两个月前,我还没学习链表的时候看到了约瑟夫环的问题,试着用面向过程的思想把它实现了今天去一个软件公司面试实习生的时候又看见了这题.... 我告诉面试官说我电脑上有自己实现的代码.可他非要我写在纸上. 然后我就做吧,结果面试的时候做题思路又完全变了.... 果然是代码写在机器上和写在纸上就完全不同了... 还是感觉自己基础太薄弱了... int main(int argc, const char * argv[]) { int child[500]; for (int i=0; i<500; i++) { child[i]=1; } int sum = 500; int position = 0; int lastPosition = 0; int number = 0; while (sum > 1) { if (child[position%500]>0) { number++; if (number == 3 ) { child[position%500] = 0; sum--; number = 0; } else{ lastPosition = position%500; } } position++; } printf("%d\n",lastPosition); return 0; } 来源： CSDN 作者：汪苏哲链接： https://blog.csdn.net

How to get the correct offset top value from webkit (Chrome/Safari) with jQuery? Webkit bug?

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I'm working on code that programmatically positions a div to give the appearance of scrolling. All works fine when using Firefox and Internet Explorer (believe it or not). However, I'm getting bogus values from webkit browsers (Chrome/Safari). It appears to have something to do with whether an element has content. I'm calculating the position of an empty anchor element. Webkit seems to get it right only when the element has visible content. So, I could work around this by having some content in my anchor. However, that messes up my layout and feels like a kludge. Also, I'd like to log a bug,

C# - Moving a control to the mouse's position

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问题 I am trying to get a control to follow the cursor when the user clicks and drag the control. The problem is that 1.) the control doesn't go to the mouse's position, and 2.) the control flickers and flies all over the place. I've tried a few different methods of doing this, but all so far have failed. I've tried: protected override void OnMouseDown(MouseEventArgs e) { while (e.Button == System.Windows.Forms.MouseButtons.Left) { this.Location = e.Location; } } and protected override void

MPMoviePlayerController play video starting from 30th sec (from mid of the video)

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问题 I am creating a simple media player using MPMoviePlayerController , here I want to play the videos from particular point like from 30th sec or 50th second onwards and also want to move the video player head to any particular point and start playing it from that point. I tried with initialPlaybackTime and MPMoviePlaybackStateSeekingForward but no luck. video is not from local, its from server. Please help me to do the same. 回答1: MPMoviePlayerController *mp; mp.initialPlaybackTime = 84; mp

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