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28 lines
13 KiB
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<!DOCTYPE html><html><head><meta charset="utf-8"><meta http-equiv="X-UA-Compatible" content="IE=edge,chrome=1"><title>React Native | Build Native Apps Using React</title><meta name="viewport" content="width=device-width"><meta property="og:title" content="React Native | Build Native Apps Using React"><meta property="og:type" content="website"><meta property="og:url" content="http://facebook.github.io/react-native/index.html"><meta property="og:image" content="http://facebook.github.io/react-native/img/opengraph.png"><meta property="og:description" content="Build Native Apps Using React"><link rel="shortcut icon" href="/react-native/img/favicon.png"><link rel="stylesheet" href="/react-native/css/react-native.css"><script type="text/javascript" src="//use.typekit.net/vqa1hcx.js"></script><script type="text/javascript">try{Typekit.load();}catch(e){}</script></head><body><div class="container"><div class="nav-main"><div class="wrap"><a class="nav-home" href="/react-native/"><img src="/react-native/img/logo.png">React Native</a><ul class="nav-site"><li><a href="/react-native/docs/getting-started.html#content" class="active">docs</a></li><li><a href="/react-native/support.html" class="">support</a></li><li><a href="http://github.com/facebook/react-native" class="">github</a></li></ul></div></div><section class="content wrap documentationContent"><div class="nav-docs"><div class="nav-docs-section"><h3>Quick Start</h3><ul><li><a style="margin-left:0;" class="" href="/react-native/docs/getting-started.html#content">Getting Started</a></li></ul></div><div class="nav-docs-section"><h3>Guides</h3><ul><li><a style="margin-left:0;" class="" href="/react-native/docs/pixels.html#content">Physical vs Logical Pixels</a></li><li><a style="margin-left:0;" class="" href="/react-native/docs/style.html#content">Style</a></li><li><a style="margin-left:0;" class="" href="/react-native/docs/nativemodulesios.html#content">Native Modules (iOS)</a></li></ul></div><div class="nav-docs-section"><h3>components</h3><ul><li><a style="margin-left:0;" class="" href="/react-native/docs/activityindicatorios.html#content">ActivityIndicatorIOS</a></li><li><a style="margin-left:0;" class="" href="/react-native/docs/datepickerios.html#content">DatePickerIOS</a></li><li><a style="margin-left:0;" class="" href="/react-native/docs/image.html#content">Image</a></li><li><a style="margin-left:0;" class="" href="/react-native/docs/listview.html#content">ListView</a></li><li><a style="margin-left:0;" class="" href="/react-native/docs/mapview.html#content">MapView</a></li><li><a style="margin-left:0;" class="" href="/react-native/docs/navigatorios.html#content">NavigatorIOS</a></li><li><a style="margin-left:0;" class="" href="/react-native/docs/pickerios.html#content">PickerIOS</a></li><li><a style="margin-left:0;" class="" href="/react-native/docs/scrollview.html#content">ScrollView</a></li><li><a style="margin-left:0;" class="" href="/react-native/docs/sliderios.html#content">SliderIOS</a></li><li><a style="margin-left:0;" class="" href="/react-native/docs/switchios.html#content">SwitchIOS</a></li><li><a style="margin-left:0;" class="" href="/react-native/docs/tabbarios.html#content">TabBarIOS</a></li><li><a style="margin-left:0;" class="" href="/react-native/docs/text.html#content">Text</a></li><li><a style="margin-left:0;" class="" href="/react-native/docs/textinput.html#content">TextInput</a></li><li><a style="margin-left:0;" class="" href="/react-native/docs/touchablehighlight.html#content">TouchableHighlight</a></li><li><a style="margin-left:0;" class="" href="/react-native/docs/touchableopacity.html#content">TouchableOpacity</a></li><li><a style="margin-left:0;" class="" href="/react-native/docs/touchablewithoutfeedback.html#content">TouchableWithoutFeedback</a></li><li><a style="margin-left:0;" class="" href="/react-native/docs/view.html#content">View</a></li><li><a style="margin-left:0;" class="" href="/react-native/docs/webview.html#content">WebView</a></li></ul></div><div class="nav-docs-section"><h3>apis</h3><ul><li><a style="margin-left:0;" class="" href="/react-native/docs/alertios.html#content">AlertIOS</a></li><li><a style="margin-left:0;" class="" href="/react-native/docs/animation.html#content">Animation</a></li><li><a style="margin-left:0;" class="" href="/react-native/docs/appregistry.html#content">AppRegistry</a></li><li><a style="margin-left:0;" class="" href="/react-native/docs/appstate.html#content">AppState</a></li><li><a style="margin-left:0;" class="" href="/react-native/docs/appstateios.html#content">AppStateIOS</a></li><li><a style="margin-left:0;" class="" href="/react-native/docs/asyncstorage.html#content">AsyncStorage</a></li><li><a style="margin-left:0;" class="" href="/react-native/docs/cameraroll.html#content">CameraRoll</a></li><li><a style="margin-left:0;" class="" href="/react-native/docs/interactionmanager.html#content">InteractionManager</a></li><li><a style="margin-left:0;" class="" href="/react-native/docs/layoutanimation.html#content">LayoutAnimation</a></li><li><a style="margin-left:0;" class="" href="/react-native/docs/netinfo.html#content">NetInfo</a></li><li><a style="margin-left:0;" class="" href="/react-native/docs/pixelratio.html#content">PixelRatio</a></li><li><a style="margin-left:0;" class="" href="/react-native/docs/statusbarios.html#content">StatusBarIOS</a></li><li><a style="margin-left:0;" class="" href="/react-native/docs/stylesheet.html#content">StyleSheet</a></li><li><a style="margin-left:0;" class="" href="/react-native/docs/vibrationios.html#content">VibrationIOS</a></li></ul></div><div class="nav-docs-section"><h3>Polyfills</h3><ul><li><a style="margin-left:0;" class="" href="/react-native/docs/network.html#content">Network</a></li><li><a style="margin-left:0;" class="active" href="/react-native/docs/timers.html#content">Timers</a></li></ul></div></div><div class="inner-content"><a id="content"></a><h1>Timers</h1><div><p>Timers are an important part of an application and React Native implements the <a href="https://developer.mozilla.org/en-US/Add-ons/Code_snippets/Timers" target="_blank">browser timers</a>.</p><h2><a class="anchor" name="timers"></a>Timers <a class="hash-link" href="#timers">#</a></h2><ul><li>setTimeout, clearTimeout</li><li>setInterval, clearInterval</li><li>setImmediate, clearImmediate</li><li>requestAnimationFrame, cancelAnimationFrame</li></ul><p><code>requestAnimationFrame(fn)</code> is the exact equivalent of <code>setTimeout(fn, 0)</code>, they are triggered right after the screen has been flushed.</p><p><code>setImmediate</code> is executed at the end of the current JavaScript execution block, right before sending the batched response back to native. Note that if you call <code>setImmediate</code> within a <code>setImmediate</code> callback, it will be executed right away, it won't yield back to native in between.</p><p>The <code>Promise</code> implementation uses <code>setImmediate</code> as its asynchronicity primitive.</p><h2><a class="anchor" name="interactionmanager"></a>InteractionManager <a class="hash-link" href="#interactionmanager">#</a></h2><p>One reason why well-built native apps feel so smooth is by avoiding expensive operations during interactions and animations. In React Native, we currently have a limitation that there is only a single JS execution thread, but you can use <code>InteractionManager</code> to make sure long-running work is scheduled to start after any interactions/animations have completed.</p><p>Applications can schedule tasks to run after interactions with the following:</p><div class="prism language-javascript">InteractionManager<span class="token punctuation">.</span><span class="token function">runAfterInteractions<span class="token punctuation">(</span></span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token operator">=</span><span class="token operator">></span> <span class="token punctuation">{</span>
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<span class="token comment" spellcheck="true"> // ...long-running synchronous task...
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</span><span class="token punctuation">}</span><span class="token punctuation">)</span><span class="token punctuation">;</span></div><p>Compare this to other scheduling alternatives:</p><ul><li>requestAnimationFrame(): for code that animates a view over time.</li><li>setImmediate/setTimeout/setInterval(): run code later, note this may delay animations.</li><li>runAfterInteractions(): run code later, without delaying active animations.</li></ul><p>The touch handling system considers one or more active touches to be an 'interaction' and will delay <code>runAfterInteractions()</code> callbacks until all touches have ended or been cancelled.</p><p>InteractionManager also allows applications to register animations by creating an interaction 'handle' on animation start, and clearing it upon completion:</p><div class="prism language-javascript"><span class="token keyword">var</span> handle <span class="token operator">=</span> InteractionManager<span class="token punctuation">.</span><span class="token function">createInteractionHandle<span class="token punctuation">(</span></span><span class="token punctuation">)</span><span class="token punctuation">;</span><span class="token comment" spellcheck="true">
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// run animation... (`runAfterInteractions` tasks are queued)
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</span><span class="token comment" spellcheck="true">// later, on animation completion:
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</span>InteractionManager<span class="token punctuation">.</span><span class="token function">clearInteractionHandle<span class="token punctuation">(</span></span>handle<span class="token punctuation">)</span><span class="token punctuation">;</span><span class="token comment" spellcheck="true">
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// queued tasks run if all handles were cleared</span></div><h2><a class="anchor" name="timermixin"></a>TimerMixin <a class="hash-link" href="#timermixin">#</a></h2><p>We found out that the primary cause of fatals in apps created with React Native was due to timers firing after a component was unmounted. To solve this recurring issue, we introduced <code>TimerMixin</code>. If you include <code>TimerMixin</code>, then you can replace your calls to <code>setTimeout(fn, 500)</code> with <code>this.setTimeout(fn, 500)</code> (just prepend <code>this.</code>) and everything will be properly cleaned up for you when the component unmounts.</p><div class="prism language-javascript"><span class="token keyword">var</span> TimerMixin <span class="token operator">=</span> <span class="token function">require<span class="token punctuation">(</span></span><span class="token string">'react-timer-mixin'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
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<span class="token keyword">var</span> Component <span class="token operator">=</span> React<span class="token punctuation">.</span><span class="token function">createClass<span class="token punctuation">(</span></span><span class="token punctuation">{</span>
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mixins<span class="token punctuation">:</span> <span class="token punctuation">[</span>TimerMixin<span class="token punctuation">]</span><span class="token punctuation">,</span>
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componentDidMount<span class="token punctuation">:</span> <span class="token keyword">function</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
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<span class="token keyword">this</span><span class="token punctuation">.</span><span class="token function">setTimeout<span class="token punctuation">(</span></span>
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<span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token operator">=</span><span class="token operator">></span> <span class="token punctuation">{</span> console<span class="token punctuation">.</span><span class="token function">log<span class="token punctuation">(</span></span><span class="token string">'I do not leak!'</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token punctuation">}</span><span class="token punctuation">,</span>
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<span class="token number">500</span>
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<span class="token punctuation">)</span><span class="token punctuation">;</span>
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<span class="token punctuation">}</span>
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<span class="token punctuation">}</span><span class="token punctuation">)</span><span class="token punctuation">;</span></div><p>We highly recommend never using bare timers and always using this mixin, it will save you from a lot of hard to track down bugs.</p></div><div class="docs-prevnext"></div></div></section><footer class="wrap"><div class="right">© 2015 Facebook Inc.</div></footer></div><div id="fb-root"></div><script>
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