Google AMP - 动画

Amp-animation 是一个 amp 组件，它定义要在其他 amp 组件上使用的动画。本章详细讨论它们。

要使用 amp-animation，我们需要添加以下脚本 -

<script async custom-element = "amp-animation" 
   src = "https://cdn.ampproject.org/v0/amp-animation-0.1.js">
</script>

动画的详细信息在 json 结构中定义。

amp-animation的基本结构如下所示 -

<amp-animation layout = "nodisplay">
   <script type = "application/json">
      {
         // Timing properties
         ...
         "animations": [
            {
               // animation 1
            },
            ...
            {
               // animation n
            }
         ]
      }
   </script>
</amp-animation>

动画组件由以下部分组成：选择器、变量、计时属性、关键帧等。

{
   "selector": "#target-id",
   // Variables
   // Timing properties
   // Subtargets
   ...
   "keyframes": []
}

选择器

这里我们需要给出将使用动画的元素的类或 id。

变量

它们是定义为在关键帧内使用的值。变量是使用var()定义的。

例子

{
   "--delay": "0.5s",
   "animations": [
      {
         "selector": "#target1",
         "delay": "var(--delay)",
         "--x": "150px",
         "--y" : "200px",
         "keyframes": {
            "transform": "translate(var(--x), var(--y, 0px)"
         }
      }
   ]
}

这里，delay、x 和y是变量，变量的值在所示示例中定义。

时序属性

您可以在此处定义动画的持续时间和延迟。以下是支持的计时属性 -

财产	价值	描述
期间	时间属性。值必须以毫秒为单位。	用于动画的持续时间。
延迟	时间属性。值必须以毫秒为单位。	动画开始执行之前的延迟
结束延迟	时间属性。值必须以毫秒或秒为单位。	动画完成时应用的指定延迟。
迭代	值必须是一个数字。	动画必须重复的次数。
迭代开始	值必须是一个数字。	效果开始动画化的时间偏移。
缓和	值是一个字符串	这用于获得动画的缓动效果。缓动的一些示例是线性、缓动、缓入、缓出、缓入出等
方向	值是一个字符串	“正常”、“反向”、“交替”或“交替反向”之一。
充满	值是一个字符串	值可以是“无”、“向前”、“向后”、“两者”、“自动”。

关键帧

关键帧可以通过多种方式定义，例如对象形式或数组形式。考虑以下示例。

例子

"keyframes": {"transform": "translate(100px,200px)"}

例子

{
   "keyframes": {

      "opacity": [1, 0],
      "transform": ["scale(1)", "scale(2)"]
   }
}

例子

{
   "keyframes": [
      {"opacity": 1, "transform": "scale(1)"},
      {"opacity": 0, "transform": "scale(2)"}
   ]
}

例子

{
   "keyframes": [
      {"easing": "ease-out", "opacity": 1, "transform": "scale(1)"},
      {"opacity": 0, "transform": "scale(2)"}
   ]
}

使用 CSS 的关键帧

<style amp-custom>
   div {
      width: 100px;
      height: 100px;
      background-color: red;
      position: relative;
      margin: 0 auto;
      transform:scale(3);
   }
   @keyframes example { 0% {transform:scale(3)}
      75% {transform:scale(2)}
      100% {transform:scale(1)}
   }

</style>

<amp-animation layout = "nodisplay">
   <script type = "application/json">
      {
         "duration": "4s",
         "keyframes": "example"
      }
   </script>
</amp-animation>

有一些 CSS 属性可以在关键帧内使用。支持的属性称为白名单属性。以下是可在关键帧内使用的白名单属性 -

不透明度
转换
能见度
'偏移距离'

注意- 使用白名单之外的任何其他属性都会在控制台中引发错误。

现在让我们通过一个简单的示例来了解，该示例将在应用动画时旋转图像。在此示例中，我们使用 amp-animation 旋转图像。

例子

<!doctype html>
<html amp lang = "en">
   <head>
      <meta charset = "utf-8">
      <script async src = "https://cdn.ampproject.org/v0.js"></script>
      <title>Google AMP - Amp Video</title>
      <link rel = "canonical" href = "http://example.ampproject.org/article-metadata.html">
      <meta name = "viewport" content = "width = device-width, minimum-scale = 1,initial-scale = 1">
   
      <style amp-boilerplate>
         body{
            -webkit-animation:
            -amp-start 8s steps(1,end) 0s 1 normal both;-moz-animation:
            -amp-start 8s steps(1,end) 0s 1 normal both;-ms
            -amp-start 8s steps(1,end) 0s 1 normal both;animation:
            -amp-start 8s steps(1,end) 0s 1 normal both
         }
         @-webkit-keyframes 
         -amp-start{from{visibility:hidden}to{visibility:visible}}@-moz-keyframes 
         -amp-start{from{visibility:hidden}to{visibility:visible}}@-ms-keyframes 
         -amp-start{from{visibility:hidden}to{visibility:visible}}@-o-keyframes 
         -amp-start{from{visibility:hidden}to{visibility:visible}}@keyframes 
         -amp-start{from{visibility:hidden}to{visibility:visible}}
      </style>
   
      <noscript>
         <style amp-boilerplate>
            body{
               -webkit-animation:none;
               -moz-animation:none;
               -ms-animation:none;
               animation:none
            }
         </style>
      </noscript>
   
      <script async custom-element = "amp-animation" 
         src =" https://cdn.ampproject.org/v0/amp-animation-0.1.js">
      </script>
      <style amp-custom>
         amp-img {
            border: 1px solid black;
            border-radius: 4px;
            padding: 5px;
         }
      </style>
   </head>
   <body>
      <h3>Google AMP - Amp Animation Example</h3>
      <amp-animation id = "anim1" layout = "nodisplay" trigger = "visibility">
         <script type = "application/json">
            {
               "duration": "1s",
               "fill": "both",
               "direction": "alternate",
               "animations": [
                  {
                     "selector": "#image1",
                     "easing": "cubic-bezier(0,0,.21,1)",
                     "keyframes": {
                        "transform": "rotate(20deg)"
                     }
                  }
               ]
            }
         </script>
      </amp-animation>
      <br/>
      <br/>
      <amp-img 
         id = "image1" 
         src = "images/christmas1.jpg" 
         width = 300 
         height = 250 
         layout = "responsive">
      </amp-img>
      <br/>
   </body>
</html>

输出

上面使用的 amp-animation 详细信息在下面所示的代码中给出 -

<amp-animation id = "anim1" layout = "nodisplay" trigger = "visibility">
   <script type = "application/json">
   {
      "duration": "1s",
      "fill": "both",
      "direction": "alternate",
      "animations": [
         {
            "selector": "#image1",
            "easing": "cubic-bezier(0,0,.21,1)",
            "keyframes": {
               "transform": "rotate(20deg)"
            }
         }
      ]
   }
   </script>
</amp-animation>

这里的选择器是应用旋转动画的图像的 id -

<amp-img 
   id = "image1" 
   src = "images/christmas1.jpg" 
   width = 300 
   height = 250 
   layout = "responsive">
</amp-img>

使用 CSS 关键帧的示例

例子

<!doctype html>
<html amp lang = "en">
   <head>
      <meta charset = "utf-8">
      <script async src = "https://cdn.ampproject.org/v0.js"></script>
      <title>Google AMP - Amp Video</title>
      <link rel = "canonical" href = "http://example.ampproject.org/article-metadata.html">
      <meta name = "viewport" content = "width = device-width,minimum-scale = 1,initial-scale = 1">
      <style amp-boilerplate>
         body{
            -webkit-animation:
            -amp-start 8s steps(1,end) 0s 1 normal both;-moz-animation:
            -amp-start 8s steps(1,end) 0s 1 normal both;-ms-animation:
            -amp-start 8s steps(1,end) 0s 1 normal both;animation:
            -amp-start 8s steps(1,end) 0s 1 normal both
         }
         @-webkit-keyframes 
         -amp-start{from{visibility:hidden}to{visibility:visible}}@-moz-keyframes 
         -amp-start{from{visibility:hidden}to{visibility:visible}}@-ms-keyframes 
         -amp-start{from{visibility:hidden}to{visibility:visible}}@-o-keyframes 
         -amp-start{from{visibility:hidden}to{visibility:visible}}@keyframes 
         -amp-start{from{visibility:hidden}to{visibility:visible}}
      </style>
      <noscript>
         <style amp-boilerplate>
            body{
               -webkit-animation:none;
               -moz-animation:none;
               -ms-animation:none;
               animation:none
            }
         </style>
      </noscript>
      <script async custom-element = "amp-animation"
         src = "https://cdn.ampproject.org/v0/amp-animation-0.1.js">
      </script>
      <style amp-custom>
         div {
            width: 100px;
            height: 100px;
            background-color: red;
            position: relative;
            margin: 0 auto;
            transform:scale(3);
         }

         @keyframes example {
            0% {transform:scale(3)}
            75% {transform:scale(2)}
            100% {transform:scale(1)}
         }
      </style>
   </head>
   <body>
      <h3>Google AMP - Amp Animation Example</h3>
      <amp-animation id = "anim1" layout = "nodisplay" trigger = "visibility">
         <script type = "application/json">
            {
               "duration": "3s",
               "fill": "both",
               "direction": "alternate",
               "animations": [{
                  "selector": "#image1",
                  "easing": "cubic-bezier(0,0,.21,1)",
                  "keyframes":"example"
               }]
            }
         </script>
      </amp-animation>
      <br/>
      <br/>
      <div id = "image1"></div>
      <br/>
   </body>
</html>

输出

动画触发

当触发器 = ”visibility” 时，默认应用动画。为了在事件上启动动画，我们必须删除触发器=“visibility”并添加事件以启动动画，如下例所示 -

例子

<!doctype html>
<html amp lang = "en">
   <head>
      <meta charset = "utf-8">
      <script async src = "https://cdn.ampproject.org/v0.js"></script>
      <title>Google AMP - Amp Video</title>
      <link rel = "canonical" href = "http://example.ampproject.org/article-metadata.html">
      <meta name = "viewport" content = "width = device-width,
      minimum-scale = 1,initial-scale = 1">
      <style amp-boilerplate>
         body{
            -webkit-animation:
            -amp-start 8s steps(1,end) 0s 1 normal both;-moz-animation:
            -amp-start 8s steps(1,end) 0s 1 normal both;-ms-animation:
            -amp-start 8s steps(1,end) 0s 1 normal both;animation:
            -amp-start 8s steps(1,end) 0s 1 normal both
         }
         @-webkit-keyframes 
         -amp-start{from{visibility:hidden}to{visibility:visible}}@-moz-keyframes 
         -amp-start{from{visibility:hidden}to{visibility:visible}}@-ms-keyframes 
         -amp-start{from{visibility:hidden}to{visibility:visible}}@-o-keyframes 
         -amp-start{from{visibility:hidden}to{visibility:visible}}@keyframes 
         -amp-start{from{visibility:hidden}to{visibility:visible}}
      </style>
      <noscript>
         <style amp-boilerplate>                      
            body{
               -webkit-animation:none;
               -moz-animation:none;
               -ms-animation:none;
               animation:none}
         </style>
      </noscript>
      <script async custom-element = "amp-animation" 
         src = "https://cdn.ampproject.org/v0/amp-animation-0.1.js">
      </script>
      <style amp-custom>
         div {
            width: 100px;
            height: 100px;
            background-color: red;
            position: relative;
            margin: 0 auto;
            transform:scale(2); 
         }
         @keyframes example {
            0% {transform:scale(2)}
            75% {transform:scale(1)}
            100% {transform:scale(0.5)}
         }
         button{ 
            background-color: #ACAD5C; 
            color: white; 
            padding: 12px 20px; 
            border: none; 
            border-radius: 4px; 
            cursor: pointer; 
            float: left;
         }
      </style>
   </head>
   <body>
      <h3>Google AMP - Amp Animation Example</h3>
      <amp-animation id = "anim1" layout = "nodisplay">
         <script type = "application/json">
            {        
               "duration": "3s",
               "fill": "both",
               "direction": "alternate",
               "animations": [{
                  "selector": "#image1",
                  "easing": "cubic-bezier(0,0,.21,1)",
                  "keyframes":"example"
               }]
            }
         </script>
      </amp-animation>
      <button on = "tap:anim1.start">Start</button>
      <br/>
      <br/>
      <div id = "image1"></div>
   </body>
</html>

请注意，点击开始按钮时动画将开始。

输出

我们使用了名为start on On 的操作来开始动画。同样，还支持其他操作，如下 -

开始
暂停
重新开始
恢复
切换暂停
寻求
撤销
结束
取消

让我们看一个可以使用该操作的工作示例。

例子

<!doctype html>
<html amp lang = "en">
   <head>
      <meta charset = "utf-8">
      <script async src = "https://cdn.ampproject.org/v0.js"></script>
      <title>Google AMP - Amp Video</title>
      <link rel = "canonical" href = "http://example.ampproject.org/article-metadata.html">
      <meta name = "viewport" content = "width=device-width,minimum-scale = 1,initial-scale = 1">
      
      <style amp-boilerplate>
         body{
            -webkit-animation:
            -amp-start 8s steps(1,end) 0s 1 normal both;-moz-animation:
            -amp-start 8s steps(1,end) 0s 1 normal both;-ms-animation:
            -amp-start 8s steps(1,end) 0s 1 normal both;animation:
            -amp-start 8s steps(1,end) 0s 1 normal both
         }
         @-webkit-keyframes 
         -amp-start{from{visibility:hidden}to{visibility:visible}}@-moz-keyframes 
         -amp-start{from{visibility:hidden}to{visibility:visible}}@-ms-keyframes 
         -amp-start{from{visibility:hidden}to{visibility:visible}}@-o-keyframes 
         -amp-start{from{visibility:hidden}to{visibility:visible}}@keyframes 
         -amp-start{from{visibility:hidden}to{visibility:visible}}
      </style>
      
      <noscript>
         <style amp-boilerplate> 
            body{
               -webkit-animation:none;
               -moz-animation:none;
               -ms-animation:none;
               animation:none}
         </style>
      </noscript>
      <script async custom-element = "amp-animation" 
         src = "https://cdn.ampproject.org/v0/amp-animation-0.1.js">
      </script>
      <style amp-custom>
         #image1 {
            width: 100px;
            height: 100px;
            background-color: red;
            position: relative;
            margin: 0 auto;
            transform:scale(2);
         }
         @keyframes example {
            0% {transform:scale(2)}
            75% {transform:scale(1)}
            100% {transform:scale(0.5)}
         }
         button1{
            background-color: #ACAD5C; 
            color: white; 
            padding: 12px 20px; 
            border: none; 
            border-radius: 4px; 
            cursor: pointer; 
            float: left;
         }
      </style>
   </head>
   <body>
      <h3>Google AMP - Amp Animation Example</h3>
      <amp-animation id = "anim1" layout = "nodisplay">
         <script type = "application/json">
            {
               "duration": "3s",
               "fill": "both",
               "direction": "alternate",
               "animations": [{
                  "selector": "#image1",
                  "easing": "cubic-bezier(0,0,.21,1)",
                  "keyframes":"example"
               }]
            }
         </script>
      </amp-animation>
      <button on = "tap:anim1.start">Start</button>
      <button on = "tap:anim1.pause">Pause</button>
      <button on = "tap:anim1.resume">Resume</button>
      <button on = "tap:anim1.reverse">Reverse</button>
      <button on = "tap:anim1.cancel">cancel</button>
      <button on = "tap:anim1.finish">finish</button>
      <button on = "tap:anim1.togglePause">togglePause</button>
      <button on = "tap:anim1.seekTo(percent = 1.00)">seekTo(100%)</button>
      <br/>
      <br/>
      <br/>
      <br/>
      <div id="image1"></div>
   </body>
</html>

输出