问题
I'm trying to get background Images to fadeIn / fadeOut when the user scrolls down the page. In the long run I'm shooting for a time lapse effect using several background images. I've got the background images changing on scroll, but I can't seem to get them to fade from one to the next.
Here is what I've got so far - jsFiddle
$(document).scroll(function () {
if ($(this).scrollTop() > 1) {
$('body').css({
backgroundImage: 'url("http://s3.amazonaws.com/dfc_attachments/images/3237846/sun1_web.png")'
});
}
if ($(this).scrollTop() > 250) {
$('body').css({
backgroundImage: 'url("http://s3.amazonaws.com/dfc_attachments/images/3237850/sun2_web.png")'
});
}
if ($(this).scrollTop() > 500) {
$('body').css({
backgroundImage: 'url("http://s3.amazonaws.com/dfc_attachments/images/3237854/sun3_web.png")'
});
}
if ($(this).scrollTop() > 750) {
$('body').css({
backgroundImage: 'url("http://s3.amazonaws.com/dfc_attachments/images/3237858/sun4_web.png")'
});
}
});
回答1:
You can't animate the background-image property. Instead, render the images with standard <img> tags and fade those in on top of one another.
回答2:
Here's how it works, for any one else having this problem.
$(document).scroll(function () {
var y = $(this).scrollTop();
if (y > 150) {
$('#img2').fadeIn();
}
else {$('#img2').fadeOut('fast')};
if (y > 300) {
$('#img3').fadeIn();
}
else {$('#img3').fadeOut('fast')};
if (y > 450) {
$('#img4').fadeIn();
}
else {$('#img4').fadeOut('fast')};
});
jsFiddle
回答3:
Used this with a bit of bug shooting for a vertical scrolling site with images replaced at each "level" as the user scrolls down. I was trying to use SuperScrollorama but after kicking it around for an hour I gave up. This is great for simple vertical "story telling" style sites.
So, firstly, in the header:
<script type="text/javascript" src="http://code.jquery.com/jquery-1.9.1.js"></script>
<script type="text/javascript">//<![CDATA[
$(window).load(function(){
$(document).scroll(function () {
var y = $(this).scrollTop();
if (y > 1013) {
$('#machine1swap').fadeIn('slow');
}
else {$('#machine1swap').fadeOut('fast')};
if (y > 2119) {
$('#machine2swap').fadeIn('slow');
}
else {$('#machine2swap').fadeOut('fast')};
if (y > 3216) {
$('#machine3swap').fadeIn({});
}
else {$('#machine3swap').fadeOut('fast')};
});
});//]]>
</script>
And the HTML
<body>
<div id="whole_body">
<div id="centre_zone">
<img src="images/1.jpg" width="960" height="822" /><img src="images/2.png" width="960" height="591" />
<div id="machine1"><div id="machine1swap"><img src="images/3_swap2.jpg" width="960" height="450" /></div><img src="images/3_swap1.jpg" width="960" height="450" /></div>
<img src="images/4.png" width="960" height="656" />
<div id="machine2"><div id="machine2swap"><img src="images/5_swap2.jpg" width="960" height="462" /></div><img src="images/5_swap1.jpg" width="960" height="462" /></div>
<img src="images/6.png" width="960" height="635" />
<div id="machine3"><div id="machine3swap"><img src="images/7_swap2.jpg" width="960" height="442" /></div><img src="images/7_swap1.jpg" width="960" height="442" /></div>
<img src="images/8_footer.png" width="960" height="392" border="0" usemap="#Map" />
</div>
</div>
</body>
You need to edit the "(y > xxxx)" parts in the header to fade in at which ever point your page needs it. I added up the two images above the swap and subtracted 400 to have it fade in at the bottom of the screen.
This may seem silly to most coders but I hope it helps any other noob like myself to get this right.
来源：https://stackoverflow.com/questions/15526944/fade-in-new-background-images-on-scroll