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<!DOCTYPE html>
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<html lang="zh">
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<head>
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<meta charset="utf-8" />
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<base href="../../../" />
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<script src="page.js"></script>
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<link type="text/css" rel="stylesheet" href="page.css" />
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</head>
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<body>
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<h1>定时器([name])</h1>
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<p class="desc">
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此类是 [page:Clock] 的替代品，具有不同的 API 设计和行为。目标是避免随着时间的推移 [page:Clock] 中变得明显的概念缺陷。
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<ul>
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<li>[name] 具有 [page:.update]() 方法，用于更新其内部状态。这使得可以在模拟步骤中多次调用 [page:.getDelta]() 和 [page:.getElapsed]() 而不会得到不同的值。
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</li>
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<li>该类使用页面可见性 API（Page Visibility API），以避免在应用程序处于非活动状态（例如切换标签或浏览器隐藏）时出现大的时间差值。</li>
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</ul>
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</p>
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<h2>导入</h2>
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<p>
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[name] 是一个附加组件，必须显式导入。请参阅 [link:#manual/introduction/Installation Installation / Addons].
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</p>
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<code>
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import { Timer } from 'three/addons/misc/Timer.js';
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</code>
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<h2>代码示例</h2>
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<code>
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const timer = new Timer();
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function animate( timestamp ) {
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requestAnimationFrame( animate );
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// timestamp is optional
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timer.update( timestamp );
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const delta = timer.getDelta();
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// do something with delta
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renderer.render( scene, camera );
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}
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</code>
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<h2>例子</h2>
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<p>
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[example:webgl_morphtargets_sphere WebGL / morphtargets / sphere]
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</p>
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<h2>构造函数</h2>
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<h3>Timer()</h3>
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<h2>方法</h2>
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<h3>[method:Number getDelta]()</h3>
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<p>
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返回以秒为单位的时间增量。
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</p>
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<h3>[method:Number getElapsed]()</h3>
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<p>
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返回经过的时间（以秒为单位）。
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</p>
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<h3>[method:this setTimescale]( [param:Number timescale] )</h3>
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<p>
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设置一个时间刻度，缩放 [page:.update]() 中的时间增量。
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</p>
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<h3>[method:this reset]()</h3>
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<p>
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重置当前模拟步骤的时间计算。
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</p>
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<h3>[method:this dispose]()</h3>
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<p>
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可用于释放所有内部资源。通常在不再需要计时器实例时调用。
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</p>
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<h3>[method:this update]( [param:Number timestamp] )</h3>
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<p>
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timestamp -- （可选）当前时间（以毫秒为单位）。可以从
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[link:https://developer.mozilla.org/en-US/docs/Web/API/window/requestAnimationFrame requestAnimationFrame]
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回调参数中获取 。如果未提供，当前时间将由 [link:https://developer.mozilla.org/en-US/docs/Web/API/Performance/now performance.now]
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确定。<br /><br />
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更新定时器的内部状态。该方法应该在每个模拟步骤以及对计时器执行查询之前调用一次（例如通过 [page:.getDelta]()）。
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</p>
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<h2>源代码</h2>
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<p>
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[link:https://github.com/mrdoob/three.js/blob/master/examples/jsm/misc/Timer.js examples/jsm/misc/Timer.js]
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</p>
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</body>
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</html>
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