Expanding circles with CSS3 animations

问题

I am trying to make it so when the page loads circles appear which is fine, but I need them to grow outwards, so small to big from the center not from the top left:

You can see what I have currently here: http://thomasbritton.co.uk/projects/ebrd/

Ideally, want this to be done in CSS but can use JS if it's easier/more stable.

Any ideas?

Here is my css also for the animation part:

.circle a {
  border-radius: 150px;
  color: #fff;
  height: 0;
  position: absolute;
  text-decoration: none;
  width: 0;
}

.circle a.grow {
  -webkit-animation-name: grow;
  -webkit-animation-duration: 2.2s;
  -webkit-animation-timing-function: ease;
  -webkit-animation-iteration-count: 1;
  -webkit-animation-direction: normal;
  -webkit-animation-delay: 0;
  -webkit-animation-play-state: running;
  -webkit-animation-fill-mode: forwards;

  -moz-animation-name: grow;
  -moz-animation-duration: 2.2s;
  -moz-animation-timing-function: ease;
  -moz-animation-iteration-count: 1;    
  -moz-animation-direction: normal;
  -moz-animation-delay: 0;
  -moz-animation-play-state: running;
  -moz-animation-fill-mode: forwards;

  animation-name: grow;
  animation-duration: 2.2s;
  animation-timing-function: ease;
  animation-iteration-count: 1; 
  animation-direction: normal;
  animation-delay: 0;
  animation-play-state: running;
  animation-fill-mode: forwards;
}

@-webkit-keyframes grow {
  0% { -moz-transform: scale(0); }
  100% { -moz-transform: scale(1); }
}

@-moz-keyframes grow {
  0% { -moz-transform: scale(0); }
  100% { -moz-transform: scale(1); height: 168px; width: 168px; }
}

@keyframes grow {
  0% { -moz-transform: scale(0); }
  100% { -moz-transform: scale(1); }
}

回答1:

Here's a crude example of what you need to do: jsfiddle.net/UxtJV/. It uses a bit of JS to add a class to animate the circle. It's width, height, top and left properties are animated and it is given position: relative.

div.circle {
    position: relative;

    width: 0px;
    height: 0px;
    top: 50px;
    left: 50px;

    -webkit-transition-duration: 2s;
    -webkit-transition-property: all;
    -webkit-transition-timing-function: ease-in-out;

    text-align: center;
    background: red;
    color: white;
    border-radius: 100%;
    padding: 20px;
    overflow: hidden;
}

div.circle.open {
    top: 0px;
    left: 0px;
    width: 100px;
    height: 100px;
}​

回答2:

To do so, your animation should involve:

1. increase width and height.
2. increase top and left.

It's a bit of a work, but it shall do exactly what you asked.

回答3:

You could try combining your animation with the translation property.

This could be another option:

transform-origin: top right; /* 50% 50% or whatever*/

as posted here...

回答4:

Just in case someone is looking for working jQuery solution, here it is...

HTML

<div class=circle1></div>

CSS

.circle1 {
    position:absolute; top:50px; left:50px;
    width: 0px; height: 0px;
    border:1px solid red;
    padding:20px;
    border-radius:50%;
}

JS

$(".circle1").mouseover(function() {
      $(this).animate({top:"0", left:"0", width:"100px", height:"100px", opacity: 0}, 200);  
}).mouseout(function() {
      $(this).animate({top:"50px", left:"50px", width:"0", height:"0", opacity: 1}, 200);
});

And here is the demo - http://jsbin.com/esiLULEb/1/

回答5:

You don't have to use Jquery or Javascript for your case, you can achieve that with pure CSS.

Do not use position property on your animated divs. That will cause you laggy animations. Instead use transform for performant animations.

<div class="circle__wrapper">
  <a class="circle" href="#"></a>
</div>

/* circle__wrapper will help you to position the div in the center of the page */
.circle__wrapper { 
  position: fixed; 
  top: 50%; 
  left: 50%; 
  -webkit-transform: translate(-50%, -50%); 
  transform: translate(-50%, -50%); 
}

.circle__wrapper a.circle { 
  display:block; 
  height: 168px; 
  width: 168px; 
  background-color: #fea733; 
  -webkit-border-radius: 50%; 
  -moz-border-radius: 50%; 
  border-radius: 50%; 
  -webkit-animation: growUp 2s 1.5s; /* You can remove 1.5s if you don't want delay */
  -moz-animation: growUp 2s 1.5s; 
  -ms-animation: growUp 2s 1.5s; 
  -o-animation: growUp 2s 1.5s; 
  animation: growUp 2s 1.5s; 
}


@-webkit-keyframes growUp {   
  0%  { -webkit-transform: scale(0); }
  100% { -webkit-transform: scale(1); }
}

@-moz-keyframes growUp {
  0%  { -moz-transform: scale(0); }
  100% { -moz-transform: scale(1); }
}

@-o-keyframes growUp {
  0%  { -o-transform: scale(0); }
  100% { -o-transform: scale(1); }
}

@-ms-keyframes growUp {
  0%  { -ms-transform: scale(0); }
  100% { -ms-transform: scale(1); }
}

@keyframes growUp {
  0%  { transform: scale(0); }
  100% { transform: scale(1); }
}

Hope this helps.

来源：https://stackoverflow.com/questions/9320658/expanding-circles-with-css3-animations