您的位置:

优化CSS布局——左浮动(upleft)实例详解

一、前言

布局是前端开发中的重要组成部分,CSS作为实现页面布局的语言,掌握好CSS布局的技巧可以让前端开发效率大大提升。本文将详细介绍CSS布局中一种重要的技巧——左浮动。

左浮动是CSS布局中常见的一种手段,其可以让某个元素浮动到其所在容器的左侧,且保持其他元素对其位置的影响。在实际开发中,我们经常会使用左浮动完成页面的布局,因此深入了解左浮动的实现原理和其优化的技巧是非常有必要的。

二、实现原理

左浮动的实现原理是通过给需要浮动的元素设置float: left;,使其浮动到其所在容器的左侧,同时其他元素会根据其位置进行排列。如果多个元素都设置了左浮动,那么它们将会在同一行内排列,当一行无法容纳更多元素时,后面的元素会自动换行。

左浮动的实现原理就是这么简单,下面我们来看一个实际的例子:

  
    <style type="text/css">
      .upleft {
        float: left;
        width: 100px;
        height: 100px;
        background-color: #f00;
        margin-right: 10px;
      }
    </style>
    <div class="upleft"></div>
    <div class="upleft"></div>
    <div class="upleft"></div>
    <div class="upleft"></div>
  

上述代码中,我们定义了一个class为“upleft”的样式,设置其宽度、高度为100px,背景色为红色,并且设置右侧外边距为10px。在HTML文档中使用4个

标签分别设置class为“upleft”,这样这4个元素就浮动到其所在容器的左侧。我们在浏览器中打开这个页面,可以看到4个红色的小方块浮动到了左侧,并且自动换行。

三、优化技巧

1. 清除浮动影响

在实际开发中,我们有时会遇到浮动元素无法撑起容器高度的问题,这时我们需要清除浮动影响。清除浮动的方法有多种,这里介绍一种比较简单的方法——使用overflow: hidden;。我们给浮动元素的父容器设置overflow: hidden;属性,就可以清除浮动影响了。

  
    <style type="text/css">
      .parent {
        overflow: hidden;
      }
      .upleft {
        float: left;
        width: 100px;
        height: 100px;
        background-color: #f00;
        margin-right: 10px;
      }
    </style>
    <div class="parent">
      <div class="upleft"></div>
      <div class="upleft"></div>
      <div class="upleft"></div>
      <div class="upleft"></div>
    </div>
  

上述代码中,我们在4个

元素的父容器中设置了overflow: hidden;属性,这样可以清除浮动影响。在浏览器中打开这个页面,可以看到4个小方块正常地浮动到了左侧,并且不会对容器造成影响。

2. 分组浮动

在实际开发中,我们有时会遇到多个浮动元素无法撑起容器高度的问题,这时我们需要对浮动元素进行分组浮动。分组浮动的实现原理就是将浮动元素按照一定的规则分成几组,每组中的元素再分别进行浮动。在每组浮动元素后面会添加一个一个空置元素<div style="clear: both;"></div>,来清除浮动影响。

  
    <style type="text/css">
      .parent {
        overflow: hidden;
      }
      .group1 {
        float: left;
        width: 100px;
        height: 100px;
        background-color: #f00;
        margin-right: 10px;
      }
      .group2 {
        float: left;
        width: 100px;
        height: 100px;
        background-color: #0f0;
        margin-right: 10px;
      }
      .clear {
        clear: both;
      }
    </style>
    <div class="parent">
      <div class="group1"></div>
      <div class="group1"></div>
      <div class="group2"></div>
      <div class="clear"></div>
      <div class="group2"></div>
      <div class="group2"></div>
      <div class="clear"></div>
    </div>
  

上述代码中,我们定义了3个class分别为“group1”、“group2”、“clear”的样式。其中“group1”和“group2”定义了浮动元素的样式,分别设置其宽、高为100px,背景色为红色和绿色,并且设置了右侧外边距为10px。我们在4个

标签后面添加了两个空置元素
,这是为了分组浮动时清除浮动影响。在浏览器中打开这个页面,可以看到不同颜色的方块正常浮动,并且不会造成容器高度的问题。

3. 右浮动与左浮动结合运用

左浮动是CSS布局中非常常见的技巧,但在一些情况下,右浮动也是非常有用的。当我们需要右对齐某个元素时,或者需要两个元素从左右分别浮动时,右浮动就可以完美解决这些问题。

  
    <style type="text/css">
      .left {
        float: left;
        width: 100px;
        height: 100px;
        background-color: #f00;
        margin-right: 10px;
      }
      .right {
        float: right;
        width: 100px;
        height: 100px;
        background-color: #0f0;
        margin-left: 10px;
      }
    </style>
    <div class="left"></div>
    <div class="right"></div>
  

上述代码中,我们定义了2个class分别为“left”和“right”的样式,“left”元素是左浮动的,而“right”元素是右浮动的。在HTML文档中先添加“left”元素再添加“right”元素,这样“left”元素就浮动到了左侧,“right”元素则浮动到了右侧。在浏览器中打开这个页面,可以看到一个红色方块浮动到了左侧,绿色方块浮动到了右侧。

四、总结

左浮动是CSS布局中非常常见的技巧,掌握好左浮动的实现原理和优化技巧对于提高前端开发效率非常有帮助。通过本文的介绍,我们可以清楚地了解到左浮动的实现原理,以及如何利用分组浮动、右浮动等技巧优化CSS布局。希望本文对大家学习CSS布局有所帮助。

优化CSS布局——左浮动(upleft)实例详解

2023-05-12
CSS左右布局详解

2023-05-19
when-present<#else>when-missing. (These only cover the last step of the expression; to cover the whole expression, use parenthesis: (myOptionalVar.foo)!myDefault, (myOptionalVar.foo)?? ---- ---- FTL stack trace ("~" means nesting-related): - Failed at: ${item.id} [in template "article/detail/index.ftl" at line 48, column 106] ---- Java stack trace (for programmers): ---- freemarker.core.InvalidReferenceException: [... Exception message was already printed; see it above ...] at freemarker.core.InvalidReferenceException.getInstance(InvalidReferenceException.java:134) at freemarker.core.EvalUtil.coerceModelToTextualCommon(EvalUtil.java:481) at freemarker.core.EvalUtil.coerceModelToStringOrMarkup(EvalUtil.java:401) at freemarker.core.EvalUtil.coerceModelToStringOrMarkup(EvalUtil.java:370) at freemarker.core.DollarVariable.calculateInterpolatedStringOrMarkup(DollarVariable.java:104) at freemarker.core.DollarVariable.accept(DollarVariable.java:63) at freemarker.core.Environment.visit(Environment.java:371) at freemarker.core.IteratorBlock$IterationContext.executedNestedContentForCollOrSeqListing(IteratorBlock.java:321) at freemarker.core.IteratorBlock$IterationContext.executeNestedContent(IteratorBlock.java:271) at freemarker.core.IteratorBlock$IterationContext.accept(IteratorBlock.java:244) at freemarker.core.Environment.visitIteratorBlock(Environment.java:645) at freemarker.core.IteratorBlock.acceptWithResult(IteratorBlock.java:108) at freemarker.core.IteratorBlock.accept(IteratorBlock.java:94) at freemarker.core.Environment.visit(Environment.java:335) at freemarker.core.Environment.visit(Environment.java:341) at freemarker.core.Environment.visit(Environment.java:341) at freemarker.core.Environment.process(Environment.java:314) at freemarker.template.Template.process(Template.java:383) at org.springframework.web.servlet.view.freemarker.FreeMarkerView.processTemplate(FreeMarkerView.java:332) at org.springframework.web.servlet.view.freemarker.FreeMarkerView.doRender(FreeMarkerView.java:266) at org.springframework.web.servlet.view.freemarker.FreeMarkerView.renderMergedTemplateModel(FreeMarkerView.java:220) at org.springframework.web.servlet.view.AbstractTemplateView.renderMergedOutputModel(AbstractTemplateView.java:181) at org.springframework.web.servlet.view.AbstractView.render(AbstractView.java:314) at org.springframework.web.servlet.DispatcherServlet.render(DispatcherServlet.java:1431) at org.springframework.web.servlet.DispatcherServlet.processDispatchResult(DispatcherServlet.java:1167) at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1106) at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:979) at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1014) at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:903) at jakarta.servlet.http.HttpServlet.service(HttpServlet.java:564) at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:885) at jakarta.servlet.http.HttpServlet.service(HttpServlet.java:658) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:205) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:149) at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:51) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:174) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:149) at com.software.filter.HttpSpiderIdentifyFilter.doFilter(HttpSpiderIdentifyFilter.java:51) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:174) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:149) at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:100) at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:116) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:174) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:149) at org.springframework.web.filter.FormContentFilter.doFilterInternal(FormContentFilter.java:93) at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:116) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:174) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:149) at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:201) at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:116) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:174) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:149) at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:167) at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:90) at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:482) at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:115) at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:93) at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:74) at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:340) at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:391) at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:63) at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:896) at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1744) at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:52) at java.base/java.lang.VirtualThread.run(VirtualThread.java:309)