Question

所以在这种情况下，我想为html制作一个标题。首先，我想隐藏标题。当我将鼠标悬停在浏览器顶部时标题显示块。这是代码

<html>
<head>
    <style type="text/css">

        .atas{
            top:0px;
            background-color: #5F5F5F;
            width: 100%;
            height: 50px;
            position: fixed;
            right:0px;
            left:0px;
            visibility: hidden;
        }
        .menu{

            text-align: center;
            width: 100%;
            height: 50px;
           background-color: red;
        }
        .menu:hover .atas{
           visibility: visible;
        }
      </style>  
</head>
<body >

    <div class="menu">Menu</div>
    <div class="atas">
        </div>

     </body>

为什么它没有显示＆＃34; atas＆＃34;当我将鼠标悬停在＆＃34;菜单上时＃div; DIV？

Answer 1

如果.atas是.menu的子div而不是.menu:hover + .atas{ visibility: visible; }，则编写css的方式将有效。它是一个兄弟姐妹所以你需要这样写

此处class MyVCWithAMap: UIViewController { ... // Track the state of the map user location property when going to background var trackUserLocation = false ... deinit { NSNotificationCenter.defaultCenter().removeObserver(self) } ... override func viewDidLoad() { super.viewDidLoad() ... // Register for notifications NSNotificationCenter.defaultCenter().addObserver(self, selector:#selector(appEnteredForeground), name:UIApplicationWillEnterForegroundNotification, object: nil) NSNotificationCenter.defaultCenter().addObserver(self, selector:#selector(appEnteredBackground), name:UIApplicationDidEnterBackgroundNotification, object: nil) } func appEnteredBackground() { // Capture map user location state viewModel.trackUserLocation = mapView.showsUserLocation mapView.showsUserLocation = false } func appEnteredForeground() { // Restore pre-snooze state mapView.showsUserLocation = viewModel.trackUserLocation } }指定下一个兄弟

Answer 2

这是Gauravs回答评论中描述的闪烁div问题的解决方案。同时将.atas div的：hover状态设置为block。

.menu:hover + .atas, .atas:hover {
  display: block;
}

这是相应的小提琴http://jsfiddle.net/Lr67ht6r/2/

为什么我不能在css中悬停显示块

2 个答案: