Timer class - dart:async library

<!DOCTYPE html> <html lang="en"> <head> <meta charset="utf-8"> <meta http-equiv="X-UA-Compatible" content="IE=edge"> <meta name="viewport" content="width=device-width, height=device-height, initial-scale=1, user-scalable=no"> <meta name="description" content="API docs for the Timer class from the dart:async library, for the Dart programming language."> <title>Timer class - dart:async library - Dart API</title> <link rel="canonical" href="https://api.dart.dev/dart-async/Timer-class.html"> <link rel="preconnect" href="https://fonts.gstatic.com"> <link href="https://fonts.googleapis.com/css2?family=Roboto+Mono:ital,wght@0,300;0,400;0,500;0,700;1,400&display=swap" rel="stylesheet"> <link href="https://fonts.googleapis.com/css2?family=Material+Symbols+Outlined:opsz,wght,FILL,GRAD@24,400,0,0" rel="stylesheet"> <link rel="stylesheet" href="../static-assets/github.css?v1"> <link rel="stylesheet" href="../static-assets/styles.css?v1"> <link rel="icon" href="../static-assets/favicon.png?v1">  <script async src="https://www.googletagmanager.com/gtag/js?id=G-VVQ8908SJ5"></script> <script> window.dataLayer = window.dataLayer || []; function gtag(){dataLayer.push(arguments);} gtag('js', new Date()); gtag('config', 'G-VVQ8908SJ5'); </script> <link rel="preconnect" href="https://fonts.googleapis.com"> <link rel="preconnect" href="https://fonts.gstatic.com" crossorigin> <link rel="preload" href="https://fonts.googleapis.com/css2?family=Google+Sans+Text:wght@400&family=Google+Sans:wght@500&display=swap" as="style"> <link rel="stylesheet" href="https://fonts.googleapis.com/css2?family=Google+Sans+Text:wght@400&family=Google+Sans:wght@500&display=swap"> <link rel="stylesheet" href="https://www.gstatic.com/glue/cookienotificationbar/cookienotificationbar.min.css"> </head> <body data-base-href="../" data-using-base-href="false" class="light-theme"> <div id="overlay-under-drawer"></div> <header id="title"> <span id="sidenav-left-toggle" class="material-symbols-outlined" role="button" tabindex="0">menu</span> <ol class="breadcrumbs gt-separated dark hidden-xs"> <li><a href="../index.html">Dart</a></li> <li><a href="../dart-async/dart-async-library.html">dart:async</a></li> <li class="self-crumb">Timer class</li> </ol> <div class="self-name">Timer</div> <form class="search navbar-right" role="search"> <input type="text" id="search-box" autocomplete="off" disabled class="form-control typeahead" placeholder="Loading search..."> </form> <div class="toggle" id="theme-button" title="Toggle brightness"> <label for="theme"> <input type="checkbox" id="theme" value="light-theme"> <span id="dark-theme-button" class="material-symbols-outlined"> dark_mode </span> <span id="light-theme-button" class="material-symbols-outlined"> light_mode </span> </label> </div> </header> <main> <div id="dartdoc-main-content" class="main-content" data-above-sidebar="dart-async/dart-async-library-sidebar.html" data-below-sidebar="dart-async/Timer-class-sidebar.html"> <div> <div id="external-links" class="btn-group"><a title="View source code" class="source-link" href="https://github.com/dart-lang/sdk/blob/88c9758ef131d430d8ce595c6bfb4c90574d3ddd/sdk/lib/async/timer.dart#L31"><span class="material-symbols-outlined">description</span></a></div> <h1><span class="kind-class">Timer</span> class <a href="https://dart.dev/language/class-modifiers#abstract" class="feature feature-abstract" title="This type can not be directly constructed.">abstract</a> <a href="https://dart.dev/language/class-modifiers#interface" class="feature feature-interface" title="This class can only be implemented (not extended or mixed in).">interface</a> </h1></div> <section class="desc markdown"> <p>A countdown timer that can be configured to fire once or repeatedly.</p> <p>The timer counts down from the specified duration to 0. When the timer reaches 0, the timer invokes the specified callback function. Use a periodic timer to repeatedly count down the same interval.</p> <p>A negative duration is treated the same as <a href="../dart-core/Duration/zero-constant.html">Duration.zero</a>. If the duration is statically known to be 0, consider using <a href="../dart-async/Timer/run.html">run</a>.</p> <pre class="language-dart"><code class="language-dart">void main() { Timer(const Duration(seconds: 5), handleTimeout); } void handleTimeout() { // callback function // Do some work. } </code></pre> <p><strong>Note:</strong> If Dart code using <a href="../dart-async/Timer-class.html">Timer</a> is compiled to JavaScript, the finest granularity available in the browser is 4 milliseconds.</p> <p>See also:</p> <ul> <li><a href="../dart-core/Stopwatch-class.html">Stopwatch</a> for measuring elapsed time.</li> </ul> </section> <section> <dl class="dl-horizontal"> <dt>Annotations</dt> <dd> <ul class="annotation-list clazz-relationships"> <li>@vmIsolateUnsendable</li> </ul> </dd> </dl> </section> <section class="summary offset-anchor" id="constructors"> <h2>Constructors</h2> <dl class="constructor-summary-list"> <dt id="Timer" class="callable"> <span class="name"><a href="../dart-async/Timer/Timer.html">Timer</a></span><span class="signature">(<span class="parameter" id="-param-duration"><span class="type-annotation"><a href="../dart-core/Duration-class.html">Duration</a></span> <span class="parameter-name">duration</span>, </span><span class="parameter" id="-param-callback"><span class="type-annotation">void</span> <span class="parameter-name">callback</span>()</span>)</span> </dt> <dd> Creates a new timer. <div class="constructor-modifier features">factory</div> </dd> <dt id="Timer.periodic" class="callable"> <span class="name"><a href="../dart-async/Timer/Timer.periodic.html">Timer.periodic</a></span><span class="signature">(<span class="parameter" id="periodic-param-duration"><span class="type-annotation"><a href="../dart-core/Duration-class.html">Duration</a></span> <span class="parameter-name">duration</span>, </span><span class="parameter" id="periodic-param-callback"><span class="type-annotation">void</span> <span class="parameter-name">callback</span>(<span class="parameter" id="callback-param-timer"><span class="type-annotation"><a href="../dart-async/Timer-class.html">Timer</a></span> <span class="parameter-name">timer</span></span>)</span>)</span> </dt> <dd> Creates a new repeating timer. <div class="constructor-modifier features">factory</div> </dd> </dl> </section> <section class="summary offset-anchor" id="instance-properties"> <h2>Properties</h2> <dl class="properties"> <dt id="hashCode" class="property inherited"> <span class="name"><a href="../dart-core/Object/hashCode.html">hashCode</a></span> <span class="signature">→ <a href="../dart-core/int-class.html">int</a></span> </dt> <dd class="inherited"> The hash code for this object. <div class="features"><span class="feature">no setter</span><span class="feature">inherited</span></div> </dd> <dt id="isActive" class="property"> <span class="name"><a href="../dart-async/Timer/isActive.html">isActive</a></span> <span class="signature">→ <a href="../dart-core/bool-class.html">bool</a></span> </dt> <dd> Returns whether the timer is still active. <div class="features"><span class="feature">no setter</span></div> </dd> <dt id="runtimeType" class="property inherited"> <span class="name"><a href="../dart-core/Object/runtimeType.html">runtimeType</a></span> <span class="signature">→ <a href="../dart-core/Type-class.html">Type</a></span> </dt> <dd class="inherited"> A representation of the runtime type of the object. <div class="features"><span class="feature">no setter</span><span class="feature">inherited</span></div> </dd> <dt id="tick" class="property"> <span class="name"><a href="../dart-async/Timer/tick.html">tick</a></span> <span class="signature">→ <a href="../dart-core/int-class.html">int</a></span> </dt> <dd> The number of durations preceding the most recent timer event. <div class="features"><span class="feature">no setter</span></div> </dd> </dl> </section> <section class="summary offset-anchor" id="instance-methods"> <h2>Methods</h2> <dl class="callables"> <dt id="cancel" class="callable"> <span class="name"><a href="../dart-async/Timer/cancel.html">cancel</a></span><span class="signature">(<wbr>) <span class="returntype parameter">→ void</span> </span> </dt> <dd> Cancels the timer. </dd> <dt id="noSuchMethod" class="callable inherited"> <span class="name"><a href="../dart-core/Object/noSuchMethod.html">noSuchMethod</a></span><span class="signature">(<wbr><span class="parameter" id="noSuchMethod-param-invocation"><span class="type-annotation"><a href="../dart-core/Invocation-class.html">Invocation</a></span> <span class="parameter-name">invocation</span></span>) <span class="returntype parameter">→ dynamic</span> </span> </dt> <dd class="inherited"> Invoked when a nonexistent method or property is accessed. <div class="features"><span class="feature">inherited</span></div> </dd> <dt id="toString" class="callable inherited"> <span class="name"><a href="../dart-core/Object/toString.html">toString</a></span><span class="signature">(<wbr>) <span class="returntype parameter">→ <a href="../dart-core/String-class.html">String</a></span> </span> </dt> <dd class="inherited"> A string representation of this object. <div class="features"><span class="feature">inherited</span></div> </dd> </dl> </section> <section class="summary offset-anchor inherited" id="operators"> <h2>Operators</h2> <dl class="callables"> <dt id="operator ==" class="callable inherited"> <span class="name"><a href="../dart-core/Object/operator_equals.html">operator ==</a></span><span class="signature">(<wbr><span class="parameter" id="==-param-other"><span class="type-annotation"><a href="../dart-core/Object-class.html">Object</a></span> <span class="parameter-name">other</span></span>) <span class="returntype parameter">→ <a href="../dart-core/bool-class.html">bool</a></span> </span> </dt> <dd class="inherited"> The equality operator. <div class="features"><span class="feature">inherited</span></div> </dd> </dl> </section> <section class="summary offset-anchor" id="static-methods"> <h2>Static Methods</h2> <dl class="callables"> <dt id="run" class="callable"> <span class="name"><a href="../dart-async/Timer/run.html">run</a></span><span class="signature">(<wbr><span class="parameter" id="run-param-callback"><span class="type-annotation">void</span> <span class="parameter-name">callback</span>()</span>) <span class="returntype parameter">→ void</span> </span> </dt> <dd> Runs the given <code>callback</code> asynchronously as soon as possible. </dd> </dl> </section> </div>  <div id="dartdoc-sidebar-left" class="sidebar sidebar-offcanvas-left">  <header id="header-search-sidebar" class="hidden-l"> <form class="search-sidebar" role="search"> <input type="text" id="search-sidebar" autocomplete="off" disabled class="form-control typeahead" placeholder="Loading search..."> </form> </header> <ol class="breadcrumbs gt-separated dark hidden-l" id="sidebar-nav"> <li><a href="../index.html">Dart</a></li> <li><a href="../dart-async/dart-async-library.html">dart:async</a></li> <li class="self-crumb">Timer class</li> </ol> <h5>dart:async library</h5> <div id="dartdoc-sidebar-left-content"></div> </div> <div id="dartdoc-sidebar-right" class="sidebar sidebar-offcanvas-right"> </div> </main> <footer> <span class="no-break"> Dart 3.5.4 </span> <span class="glue-footer"> <span class="no-break"> | <a href="https://dart.dev/terms" title="Terms of use">Terms</a> </span> <span class="no-break"> | <a href="https://policies.google.com/privacy" target="_blank" rel="noopener" title="Privacy policy" class="no-automatic-external">Privacy</a> </span> <span class="no-break"> | <a href="https://dart.dev/security" title="Security philosophy and practices">Security</a> </span> <div class="copyright" style="font-size: 0.9em; color: darkgrey; margin-top: 0.5em;"> Except as otherwise noted, this site is licensed under a <a style="color: darkgrey;" 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Timer class - dart:async library - Dart API