使用 CSS 实现页面加载的淡入效果
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Using CSS for a fade-in effect on page load
提问by user1556266
Can CSS transitions be used to allow a text paragraph to fade-in on page load?
可以使用 CSS 过渡来允许文本段落在页面加载时淡入吗？
I really like how it looked on http://dotmailapp.com/and would love to use a similar effect using CSS. The domain has since been purchased and no longer has the effect mentioned. An archived copy can be viewed on the Wayback Machine.
我真的很喜欢它在http://dotmailapp.com/ 上的样子，并且很想使用 CSS 来使用类似的效果。该域名已被购买，不再具有上述效果。可以在 Wayback Machine 上查看存档副本。
Illustration
插图
Having this markup:
有这个标记：
<div id="test">
<p>?This is a test</p>
</div>??????????????????????????????????????????????????????
With the following CSS rule:
使用以下 CSS 规则：
#test p {
opacity: 0;
margin-top: 25px;
font-size: 21px;
text-align: center;
-webkit-transition: opacity 2s ease-in;
-moz-transition: opacity 2s ease-in;
-o-transition: opacity 2s ease-in;
-ms-transition: opacity 2s ease-in;
transition: opacity 2s ease-in;
}?
How can the transition be triggered on load?
如何在加载时触发转换？
回答by A.M.K
Method 1:
方法一：
If you are looking for a self-invoking transition then you should use CSS 3 Animations. They aren't supported either, but this is exactly the kind of thing they were made for.
如果您正在寻找自调用过渡，那么您应该使用CSS 3 Animations。它们也不受支持，但这正是它们的用途。
CSS
CSS
#test p {
margin-top: 25px;
font-size: 21px;
text-align: center;
-webkit-animation: fadein 2s; /* Safari, Chrome and Opera > 12.1 */
-moz-animation: fadein 2s; /* Firefox < 16 */
-ms-animation: fadein 2s; /* Internet Explorer */
-o-animation: fadein 2s; /* Opera < 12.1 */
animation: fadein 2s;
}
@keyframes fadein {
from { opacity: 0; }
to { opacity: 1; }
}
/* Firefox < 16 */
@-moz-keyframes fadein {
from { opacity: 0; }
to { opacity: 1; }
}
/* Safari, Chrome and Opera > 12.1 */
@-webkit-keyframes fadein {
from { opacity: 0; }
to { opacity: 1; }
}
/* Internet Explorer */
@-ms-keyframes fadein {
from { opacity: 0; }
to { opacity: 1; }
}
/* Opera < 12.1 */
@-o-keyframes fadein {
from { opacity: 0; }
to { opacity: 1; }
}
Demo
演示
Browser Support
浏览器支持
All modern browsers and Internet Explorer 10 (and later): http://caniuse.com/#feat=css-animation
所有现代浏览器和 Internet Explorer 10（及更高版本）：http: //caniuse.com/#feat=css-animation
Method 2:
方法二：
Alternatively, you can use jQuery (or plain JavaScript; see the third code block) to change the class on load:
或者，您可以使用 jQuery（或纯 JavaScript；请参阅第三个代码块）在加载时更改类：
jQuery
jQuery
$("#test p").addClass("load");?
CSS
CSS
#test p {
opacity: 0;
font-size: 21px;
margin-top: 25px;
text-align: center;
-webkit-transition: opacity 2s ease-in;
-moz-transition: opacity 2s ease-in;
-ms-transition: opacity 2s ease-in;
-o-transition: opacity 2s ease-in;
transition: opacity 2s ease-in;
}
#test p.load {
opacity: 1;
}
Plain JavaScript (not in the demo)
纯 JavaScript（不在演示中）
document.getElementById("test").children[0].className += " load";
Demo
演示
Browser Support
浏览器支持
All modern browsers and Internet Explorer 10 (and later): http://caniuse.com/#feat=css-transitions
所有现代浏览器和 Internet Explorer 10（及更高版本）：http: //caniuse.com/#feat=css-transitions
Method 3:
方法三：
Or, you can use the method that .Mailuses:
或者，您可以使用.Mail使用的方法：
jQuery
jQuery
$("#test p").delay(1000).animate({ opacity: 1 }, 700);?
CSS
CSS
#test p {
opacity: 0;
font-size: 21px;
margin-top: 25px;
text-align: center;
}
Demo
演示
Browser Support
浏览器支持
jQuery 1.x: All modern browsers and Internet Explorer 6 (and later): http://jquery.com/browser-support/
jQuery 2.x: All modern browsers and Internet Explorer 9 (and later): http://jquery.com/browser-support/
jQuery 1.x：所有现代浏览器和 Internet Explorer 6（及更高版本）：http: //jquery.com/browser-support/
jQuery 2.x：所有现代浏览器和 Internet Explorer 9（及更高版本）：http:// jquery.com/browser-support/
This method is the most cross-compatible as the target browser does not need to support CSS 3 transitions oranimations.
这种方法是最具交叉兼容性的，因为目标浏览器不需要支持 CSS 3 过渡或动画。
回答by Ned
You can use the onload=""HTML attribute and use JavaScript to adjust the opacity style of your element.
您可以使用onload=""HTML 属性并使用 JavaScript 来调整元素的不透明度样式。
Leave your CSS as you proposed. Edit your HTML code to:
按照您的建议保留您的 CSS。将您的 HTML 代码编辑为：
<body onload="document.getElementById(test).style.opacity='1'">
<div id="test">
<p>?This is a test</p>
</div>
</body>
This also works to fade-in the complete page when finished loading:
这也适用于在完成加载后淡入整个页面：
HTML:
HTML：
<body onload="document.body.style.opacity='1'">
</body>
CSS:
CSS：
body{
opacity: 0;
transition: opacity 2s;
-webkit-transition: opacity 2s; /* Safari */
}
Check the W3Schoolswebsite: transitionsand an article for changing styles with JavaScript.
查看W3Schools网站：transitions和一篇使用 JavaScript 更改样式的文章。
回答by Rob
In response to @A.M.K's question about how to do transitions without jQuery. A very simple example I threw together. If I had time to think this through some more, I might be able to eliminate the JavaScript code altogether:
回应@AMK 关于如何在没有 jQuery 的情况下进行转换的问题。我拼凑了一个非常简单的例子。如果我有时间再考虑一下，我也许可以完全消除 JavaScript 代码：
<style>
body {
background-color: red;
transition: background-color 2s ease-in;
}
</style>
<script>
window.onload = function() {
document.body.style.backgroundColor = '#00f';
}
</script>
<body>
<p>test</p>
</body>
