首页手记 CSS3中用background-image实现粒子动画效果

CSS3中用background-image实现粒子动画效果

标签：

Html/CSS Html5 CSS3

前言

继续前几天的文章《王者荣耀匹配人员加载页面动画用纯CSS撸出来，你信吗？》，添加按钮、背景粒子动画效果。

其实在码代码的时候会发现，很多东西都是殊途同归的，方法千千万，能解决问题的都是好办法，不一定非要把代码写的特别高深，这样反而后来的人看不懂，维护根据头疼。

所以用最简单通俗的代码，更能利于后期的维护开发。

ok！先来看看背景粒子动画效果预览图：

以下代码都是基于前一篇文章《王者荣耀匹配人员加载页面动画用纯CSS撸出来，你信吗？》的，所以没有了解的可以先去看看这篇文章。

按钮点击粒子动画

<div class="button">
  <div class="button-text">确认</div>
</div>

由于按钮是梯形的，之前代码在button选择器上面已经加了伪类来实现梯形了，所以我们只能再套一层元素（button-text）来实现粒子。

.button-text {
  position: relative;
  width: 100%;
  border-radius: 4px;
  border: none;
  cursor: pointer;
}
.button-text:before, 
.button-text:after {
  position: absolute;
  content: '';
  display: block;
  width: 140%;
  height: 100%;
  left: -20%;
  z-index: -1000;
  background-repeat: no-repeat;
}
.button-text:before {
  display: none;
  top: -75%;
  background-image: 
    radial-gradient(circle, #fff 20%, transparent 20%), 
    radial-gradient(circle, transparent 20%, #fff 20%, transparent 30%), 
    radial-gradient(circle, #fff 20%, transparent 20%), 
    radial-gradient(circle, #fff 20%, transparent 20%), 
    radial-gradient(circle, transparent 10%, #fff 15%, transparent 20%), 
    radial-gradient(circle, #fff 20%, transparent 20%), 
    radial-gradient(circle, #fff 20%, transparent 20%), 
    radial-gradient(circle, #fff 20%, transparent 20%), 
    radial-gradient(circle, #fff 20%, transparent 20%);
  background-size: 
    10% 10%, 
    20% 20%, 
    15% 15%, 
    20% 20%, 
    18% 18%, 
    10% 10%, 
    15% 15%, 
    10% 10%, 
    18% 18%;
}
.button-text:after {
  display: none;
  bottom: -75%;
  background-image: 
    radial-gradient(circle, #fff 20%, transparent 20%), 
    radial-gradient(circle, #fff 20%, transparent 20%), 
    radial-gradient(circle, transparent 10%, #fff 15%, transparent 20%), 
    radial-gradient(circle, #fff 20%, transparent 20%), 
    radial-gradient(circle, #fff 20%, transparent 20%), 
    radial-gradient(circle, #fff 20%, transparent 20%), 
    radial-gradient(circle, #fff 20%, transparent 20%);
  background-size: 
    15% 15%, 
    20% 20%, 
    18% 18%, 
    20% 20%, 
    15% 15%, 
    10% 10%, 
    20% 20%;
}
.button-text:active {
  transform: scale(0.9);
}

在button-text的伪类元素上面，添加background-image,并用径向渐变radial-gradient画出多个圆作为粒子。

transform: scale(0.9)，是鼠标点击时，缩放button-text元素。

大家应该都看到默认伪类元素是display: none;隐藏的。所有当我们点击时，需要添加一个选择器，让其显示出来，并执行动画。

js来监听点击事件，点击后添加animate选择器。

var animateButton = function(e) {
  e.preventDefault;
  e.target.classList.remove('animate');
  e.target.classList.add('animate');
  setTimeout(function(){
    e.target.classList.remove('animate');
  },700);
};

var classname = document.getElementsByClassName("button-text");
for (var i = 0; i < classname.length; i++) {
  classname[i].addEventListener('click', animateButton, false);
}

然后我们添加CSS，开始动画

.button-text.animate:before {
  display: block;
  animation: topBubbles ease-in-out 0.75s forwards;
}
.button-text.animate:after {
  display: block;
  animation: bottomBubbles ease-in-out 0.75s forwards;
}
@keyframes topBubbles {
  0% {
    background-position: 
      5% 90%, 
      10% 90%, 
      10% 90%, 
      15% 90%, 
      25% 90%, 
      25% 90%, 
      40% 90%, 
      55% 90%, 
      70% 90%;
  }
  50% {
    background-position: 
      0% 80%, 
      0% 20%, 
      10% 40%, 
      20% 0%, 
      30% 30%, 
      22% 50%, 
      50% 50%, 
      65% 20%, 
      90% 30%;
  }
  100% {
    background-position: 
      0% 70%, 
      0% 10%, 
      10% 30%, 
      20% -10%, 
      30% 20%, 
      22% 40%, 
      50% 40%, 
      65% 10%, 
      90% 20%;
    background-size: 
      0% 0%, 
      0% 0%,  
      0% 0%,  
      0% 0%,  
      0% 0%,  
      0% 0%;
  }
}
@keyframes bottomBubbles {
  0% {
    background-position: 
      10% -10%,
      30% 10%,
      55% -10%,
      70% -10%,
      85% -10%,
      70% -10%,
      70% 0%;
  }
  50% {
    background-position: 
      0% 80%,
      20% 80%,
      45% 60%,
      60% 100%,
      75% 70%,
      95% 60%,
      105% 0%;
  }
  100% {
    background-position: 
      0% 90%,
      20% 90%,
      45% 70%,
      60% 110%,
      75% 80%,
      95% 70%,
      110% 10%;
    background-size: 
      0% 0%,
      0% 0%,
      0% 0%,
      0% 0%,
      0% 0%,
      0% 0%;
  }
}

我们通过background-position改变背景的位置，用background-size改变大小，来形成动画效果。

这样就形成按钮点击粒子动画效果了。

同理，我们可以在背景上面添加同样的粒子效果。代码基本可以copy。

背景粒子效果

.king:before {
  position: absolute;
  content: '';
  display: block;
  width: 100%;
  height: 100%;
  top: 0;
  z-index: 1;
  background-repeat: no-repeat;
  opacity: 0.4;
}
.king:before {
  background-image: 
    radial-gradient(circle, #fff 20%, transparent 20%), 
    radial-gradient(circle, transparent 20%, #fff 20%, transparent 30%), 
    radial-gradient(circle, #fff 20%, transparent 20%), 
    radial-gradient(circle, #fff 20%, transparent 20%), 
    radial-gradient(circle, transparent 10%, #fff 15%, transparent 20%), 
    radial-gradient(circle, #fff 20%, transparent 20%), 
    radial-gradient(circle, #fff 20%, transparent 20%), 
    radial-gradient(circle, #fff 20%, transparent 20%), 
    radial-gradient(circle, #fff 20%, transparent 20%);
  background-size: 
    10% 10%, 
    12% 12%, 
    5% 5%, 
    12% 12%, 
    5% 5%, 
    10% 10%, 
    5% 5%, 
    10% 10%, 
    5% 5%;
  display: block;
  animation: topBubbles ease-in-out 3s forwards infinite;
}