CSS - 伪类 :focus

CSS 中的 :focus 伪类表示已获得焦点的元素。此类通常在用户单击、点击元素或使用键盘的 Tab 键选择元素时触发。

:focus 伪类应用于 focussed 元素本身。要选择包含聚焦元素的元素，请使用 :focus-within 伪类。

语法


selector:focus{ properties }

CSS :focus 示例

以下示例演示了在链接上使用伪类 :focus 。单击链接或按 Tab 键可查看链接上的样式更改。


<html>
<head>
<style>
	 	 a {
	 	 	 	 color: darkviolet;
	 	 	 	 transition: all 0.3s ease;
	 	 }

	 	 a:focus {
	 	 	 	 outline: none;
	 	 	 	 color: red;
	 	 	 	 background-color: yellow;
	 	 }

	 	 body {
	 	 	 	 margin: 5px;
	 	 	 	 padding: 2rem;
	 	 	 	 display: grid;
	 	 	 	 font: 20px/1.4 system-ui, -apple-system, sans-serif;
	 	 }
</style>
</head>
<body>
	 	 <p>The link here has a <a href="#0">change in background and foreground color</a> as it is focused.</p>
</body>
</html>

以下示例演示了在按钮上使用伪类 :focus 。单击按钮以查看按钮的样式更改。


<html>
<head>
<style>
	 	button {
	 	 	 display: block;
	 	 	 margin: 2em;
	 	 	 padding: 2px;
	 	 	 font-weight: bold;
	 	 	 font-size: 18px;
	 	 	 text-align: center;
	 	 	 color: black;
	 	 	 background-color: #fff;
	 	 	 border: 2px solid black;
	 	 	 border-radius: 24px;
	 	 	 cursor: pointer;
	 	 	 transition: all 0.3s ease;
	 	 	 width: 150px;
	 	 	 height: 50px;
	 	}
	 	button:hover {
	 	 	 color: blue;
	 	 	 border-color: black;
	 	 	 background-color: lightpink;
	 	}
	 	button:focus {
	 	 	 background-color: darkred;
	 	 	 color: white;
	 	 	 border-radius: 2px;
	 	}
</style>
</head>
<body>
	 	 <button>Click Me!!</button>
</body>
</html>

以下示例演示了在输入上使用伪类 :focus 。在输入框中单击以查看输入框中的样式更改。


<html>
<head>
<style>
	 	label {
	 	 	 display: block;
	 	 	 font-size: 20px;
	 	 	 color: black;
	 	 	 width: 500px;
	 	}

	 	input[type="text"] {
	 	 	 padding: 10px 16px;
	 	 	 font-size: 16px;
	 	 	 color: black;
	 	 	 background-color: #fff;
	 	 	 border: 1px solid #597183;
	 	 	 border-radius: 8px;
	 	 	 margin-top: 5px;
	 	 	 width: 500px;
	 	 	 transition: all 0.3s ease;
	 	}

	 	input[type="text"]:focus {
	 	 	 background-color: lightyellow;
	 	}
</style>
</head>
<body>
	 	<form>
	 	 	 <label>
	 	 	 	 	Full Name
	 	 	 <input type="text">
	 	 	 </label>
	 	</form>
</body>
</html>

以下示例演示了在下拉列表上使用伪类 :focus 。单击下拉列表可查看下拉列表的样式更改。


<html>
<head>
<style>
	 	label {
	 	 	 display: block;
	 	 	 font-size: 18px;
	 	 	 color: black;
	 	 	 width: 500px;
	 	}

	 	select {
	 	 	 padding: 10px 16px;
	 	 	 font-size: 16px;
	 	 	 color: black;
	 	 	 background-color: #fff;
	 	 	 border: 1px solid #597183;
	 	 	 border-radius: 8px;
	 	 	 margin-top: 25px;
	 	 	 width: 300px;
	 	 	 transition: all 0.3s ease;
	 	}

	 	select:focus {
	 	 	 background-color: rgb(173, 233, 209);
	 	 	 box-shadow: 20px 15px 30px yellow, -20px 15px 30px lime, -20px -15px 30px blue, 20px -15px 30px red;
	 	}
</style>
</head>
<body>
	 	<form>
	 	 	 <label>
	 	 	 	 	Ice cream Flavors:
	 	 	 	 	<select name="flavor">
	 	 	 	 	 	 <option>Cookie dough</option>
	 	 	 	 	 	 <option>Pistachio</option>
	 	 	 	 	 	 <option>Cookies & Cream</option>
	 	 	 	 	 	 <option>Cotton Candy</option>
	 	 	 	 	 	 <option>Lemon & Raspberry Sorbet</option>
	 	 	 	 	 </select>
	 	 	 </label>
	 	</form>
</body>
</html>

以下示例演示了在切换开关上使用伪类 :focus 。选中该复选框以查看切换开关的样式更改。


<html>
<head>
<style>
.toggle {
	 position: relative;
	 display: block;
	 width: 100%;
	 margin: 2em;
}

.toggle label {
	 padding-right: 8px;
	 font-family: Verdana, Geneva, Tahoma, sans-serif;
	 font-size: 16px;
	 line-height: 28px;
	 color: black;
}

.toggle span {
	 position: relative;
	 display: inline-block;
	 vertical-align: middle;
	 cursor: pointer;
}

.toggle span:before {
	 display: block;
	 width: 50px;
	 height: 30px;
	 content: "";
	 background-color: #a9adaf;
	 border-radius: 28px;
	 transition: background-color 0.3s ease;
}

.toggle span:after {
	 position: absolute;
	 top: 1px;
	 left: 1px;
	 display: block;
	 width: 30px;
	 height: 28px;
	 visibility: visible;
	 content: "";
	 background-color: #fff;
	 border-radius: 28px;
	 transition: left 0.3s ease;
}

input[type="checkbox"]:checked ~ span:before {
	 background-color: orange;
}

input[type="checkbox"]:checked ~ span:after {
	 top: 1px;
	 left: 21px;
}

input[type="checkbox"]:hover ~ span:before {
	 background-color: #1194d1;
}

input[type="checkbox"]:not(:checked):hover ~ span:before {
	 background-color: #afbec9;
}

input[type="checkbox"]:focus ~ span:before {
	 outline: none;
	 box-shadow: 0 0 0 4px red;
}
</style>
</head>
<body>
	 	 <div class="toggle">
	 	 	 <label for="toggle1">Check the box to toggle me</label>
	 	 	 <input type="checkbox" id="toggle1" />
	 	 	 <span></span>
	 	 </div>
</body>
</html>

除了伪类 :focus 之外，还有两个伪类与伪类 :focus 相关联。它们列在下表中：

sr.no	伪类	描述
1	:focus-visible	焦点明显地集中在元素上，并显示给用户。
2	:focus-within	将焦点设置在包含聚焦元素的元素上。

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