Google AMP - 动画

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amp-animation 是一个 AMP 组件，用于定义可在其他 AMP 组件上使用的动画。本章将详细讨论它们。

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>

动画的详细信息定义在 JSON 结构内。

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>

animation 组件包含以下内容：选择器、变量、时间属性、关键帧等。

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

选择器

这里需要指定将使用动画的元素的类或 ID。

变量

它们是在关键帧内定义并使用的值。变量使用var()定义。

示例

{
   "--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。

时间属性

在这里，您可以为动画定义持续时间和延迟。支持以下时间属性：

属性 值 描述
duration 时间属性。值必须以毫秒为单位。 动画使用的持续时间。
delay 时间属性。值必须以毫秒为单位。 动画开始执行之前的延迟
endDelay 时间属性。值必须以毫秒或秒为单位。 动画完成后应用的延迟。
iterations 值必须为数字。 动画需要重复的次数。
iterationStart 值必须为数字。 效果开始动画的时间偏移量。
easing 值为字符串 用于为动画获得缓动效果。缓动的一些示例包括 linear、ease、ease-in、ease-out、ease-in-out 等
direction 值为字符串 "normal"、"reverse"、"alternate" 或 "alternate-reverse" 之一。
fill 值为字符串 值可以是 "none"、"forwards"、"backwards"、"both"、"auto"。

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。请考虑以下示例。

示例

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

示例

{
   "keyframes": {

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

示例

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

示例

{
   "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>

关键帧内可以使用一些 CSS 属性。支持的属性称为白名单属性。以下是在关键帧内可以使用白名单属性：

  • opacity (不透明度)
  • transform (变换)
  • visibility (可见性)
  • 'offsetDistance'

注意 - 使用除白名单属性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一下，该示例将在应用动画时旋转图像。在这个示例中，我们使用 amp-animation 旋转图像。

示例

<!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

Rotate Image

上面使用的 amp-animation 详细信息在下面显示的代码中给出：

<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>

使用来自 CSS 的关键帧的示例

示例

<!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

AMP Keyframes

动画触发器

使用 trigger = ”visibility”，动画默认应用。为了在事件上启动动画，我们必须删除 trigger = ”visibility” 并添加事件以启动动画，如下例所示：

示例

<!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，动画将在点击“开始”按钮时启动。

输出

Animation Trigger

我们在 On 上使用了名为start 的动作来启动动画。类似地，还支持其他动作，如下所示：

  • start (开始)
  • pause (暂停)
  • restart (重新开始)
  • resume (继续)
  • togglePause (切换暂停)
  • seekTo (跳转到)
  • reverse (反转)
  • finish (结束)
  • cancel (取消)

让我们看一个可以应用该动作的实际示例。

示例

<!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

Animation Start
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