使用 Javascript 和 RGBA 更改背景颜色渐变

Question

正在尝试改变我的 header 的背景颜色。想法是当页面从顶部向下滚动到 150 像素时，颜色从纯色变为渐变。所以我不确定这段代码在这里是否正确.....

jQuery(window).scroll(function() {
    if (jQuery(this).scrollTop() > 150) {
         jQuery('.site-header').css({'background': 'rgba(255,255,255,1)', 'background': '-moz-linear-gradient(top, rgba(255,255,255,1) 0%, rgba(255,255,255,1) 65%, rgba(255,255,255,0) 100%)', 'background': '-webkit-gradient(left top, left bottom, color-stop(0%, rgba(255,255,255,1)), color-stop(65%, rgba(255,255,255,1)), color-stop(100%, rgba(255,255,255,0)));', 'background': '-webkit-linear-gradient(top, rgba(255,255,255,1) 0%, rgba(255,255,255,1) 65%, rgba(255,255,255,0) 100%);', 'background': '-o-linear-gradient(top, rgba(255,255,255,1) 0%, rgba(255,255,255,1) 65%, rgba(255,255,255,0) 100%);', 'background': '-ms-linear-gradient(top, rgba(255,255,255,1) 0%, rgba(255,255,255,1) 65%, rgba(255,255,255,0) 100%)', 'background': 'linear-gradient(to bottom, rgba(255,255,255,1) 0%, rgba(255,255,255,1) 65%, rgba(255,255,255,0) 100%)', 'filter': 'progid:DXImageTransform.Microsoft.gradient( startColorstr='#ffffff', endColorstr='#ffffff', GradientType=0 )' }); 
    }
});

这是 HTML 的简化版本：

<header id="masthead" class="site-header banner" role="banner"></header>

和初始CSS：

.site-header { background: rgba(255,255,255,1); transition: background .25s ease-in-out; -moz-transition: background .25s ease-in-out; -webkit-transition: background .25s ease-in-out;position: fixed; display: block; margin: 0 0 30px 0; width: 100%; z-index: 1; }

我的想法是，我最终想通过淡化实现从渐变到纯色背景的 CSS 过渡。

知道我的代码哪里出错了吗？

Answer 1

只需尝试用 adding/removing a class 覆盖背景属性，就像这样：

在 :

中添加您的渐变背景属性

CSS

.gradientClass
{
  ......
}

添加删除上面 class 如下：

JQuery

jQuery(window).scroll(function() {
    if (jQuery(this).scrollTop() > 150) {
         jQuery('.site-header').addClass('gradientClass');
    }
    else{
         jQuery('.site-header').removeClass('gradientClass');
    }

});

Answer 2

用不同的棘手解决方案再次回答整个问题。既然你用的是JQuery，这是最好的技巧。

技巧：

我们将放置一个带有渐变背景的虚拟div。这将介于 <header> 和你的另一个 internal-div 之间（你需要添加它来保存你的 header 内容）。

现在我们有 header 上面是一个 虚拟 div 上面是你的 header的内容都是互相重叠的。它们堆叠如下：

Header（下）> Dummy-div（中）> Menu-div（上）

所以最初这个名为 .overlay 的虚拟 div 是隐藏使用 JQuery，所以现在当你 滚动到150 从顶部开始这个带有渐变的虚拟 div 将 fade-in()

DEMO.

function overlayHeight(){    
var hOfHead = $('header').outerHeight();
$('.overlay').css('height', hOfHead + 'px');
}

overlayHeight();

$(window).on('resize', function(){
   overlayHeight();
});

$('.overlay').hide();

$(window).scroll(function(){
    
    if ($(this).scrollTop() > 150)
    {
     $('.overlay').fadeIn('slow');
    }
    
    if($(this).scrollTop() < 150)
    {
       $('.overlay').fadeOut('slow');
    } 
});

/* CSSTerm.com Simple CSS menu */

body
{
    width:100%;
    margin:0px;
}
header
{
    position:fixed;
    margin:0px;
    top:0px;
    width:100%;
    background:#2b2937;
    z-index:999;
}

header .overlay
{
    display:inline-block;
    position:absolute;
    width:100%;
    left:0px;
    right:0px;    
    background: -webkit-linear-gradient(red, blue); /* For Safari 6.1 to 6.0 */
    background: -o-linear-gradient(red, blue); /* For Opera 11.1 to 12.0 */
    background: -moz-linear-gradient(red, blue); /* For Firefox 3.6 to 15 */
    background: linear-gradient(red, blue); /* Standard syntax (must be last) */
    z-index:-1;
}

.menu
{
    margin:0px;
    width:100%;
    z-index:999;
}

.menu ul 
{
    text-align:center;
    width:100%;
    padding:0px;
    margin:0px;
    list-style:none;
}

.menu ul li
{
    display:inline-block;
    padding:10px 35px;
}

a{
    color:white;
    text-decoration:none;
}

p{
    position:relative;
    padding:20px;
}

<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.9.1/jquery.min.js"></script>
<header id="masthead" class="site-header banner" role="banner">
    <span class="overlay"></span>
    <span class="menu">
        <ul>
            <li><a href="#">Link 1</a></li>
            <li><a href="#">Link 2</a></li>
            <li><a href="#">Link 3</a></li>
            <li><a href="#">Link 4</a></li> 
            <li><a href="#">Link 5</a></li>
        </ul>
    </span>
</header>
<br>
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使用 Javascript 和 RGBA 更改背景颜色渐变

Changes background color gradient using Javascript and RGBA

javascript

css

jquery

gradient