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<!DOCTYPE html><html lang="en"><head><meta charSet="utf-8"/><meta http-equiv="X-UA-Compatible" content="IE=edge"/><title>State · React Native</title><meta name="viewport" content="width=device-width"/><meta name="generator" content="Docusaurus"/><meta name="description" content="<p>There are two types of data that control a component: <code>props</code> and <code>state</code>. <code>props</code> are set by the parent and they are fixed throughout the lifetime of a component. For data that is going to change, we have to use <code>state</code>.</p>
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"/><meta name="docsearch:version" content="0.60"/><meta name="docsearch:language" content="en"/><meta property="og:title" content="State · React Native"/><meta property="og:type" content="website"/><meta property="og:url" content="https://facebook.github.io/react-native/"/><meta property="og:description" content="<p>There are two types of data that control a component: <code>props</code> and <code>state</code>. <code>props</code> are set by the parent and they are fixed throughout the lifetime of a component. For data that is going to change, we have to use <code>state</code>.</p>
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class="navListItem"><a class="navItem" href="/react-native/docs/using-a-scrollview">Using a ScrollView</a></li><li class="navListItem"><a class="navItem" href="/react-native/docs/using-a-listview">Using List Views</a></li><li class="navListItem"><a class="navItem" href="/react-native/docs/network">Networking</a></li><li class="navListItem"><a class="navItem" href="/react-native/docs/more-resources">More Resources</a></li></ul></div><div class="navGroup"><h3 class="navGroupCategoryTitle collapsible">Guides<span class="arrow"><svg width="24" height="24" viewBox="0 0 24 24"><path fill="#565656" d="M7.41 15.41L12 10.83l4.59 4.58L18 14l-6-6-6 6z"></path><path d="M0 0h24v24H0z" fill="none"></path></svg></span></h3><ul class="hide"><li class="navListItem"><a class="navItem" href="/react-native/docs/optimizing-flatlist-configuration">Optimizing Flatlist Configuration</a></li><li class="navListItem"><a class="navItem" href="/react-native/docs/components-and-apis">Components and APIs</a></li><li class="navListItem"><a class="navItem" href="/react-native/docs/platform-specific-code">Platform Specific Code</a></li><li class="navListItem"><a class="navItem" href="/react-native/docs/navigation">Navigating Between Screens</a></li><li class="navListItem"><a class="navItem" href="/react-native/docs/images">Images</a></li><li class="navListItem"><a class="navItem" href="/react-native/docs/animations">Animations</a></li><li class="navListItem"><a class="navItem" href="/react-native/docs/accessibility">Accessibility</a></li><li class="navListItem"><a class="navItem" href="/react-native/docs/improvingux">Improving User Experience</a></li><li class="navListItem"><a class="navItem" href="/react-native/docs/timers">Timers</a></li><li class="navListItem"><a class="navItem" href="/react-native/docs/debugging">Debugging</a></li><li class="navListItem"><a class="navItem" href="/react-native/docs/performance">Performance</a></li><li class="navListItem"><a class="navItem" href="/react-native/docs/gesture-responder-system">Gesture Responder System</a></li><li class="navListItem"><a class="navItem" href="/react-native/docs/javascript-environment">JavaScript Environment</a></li><li class="navListItem"><a class="navItem" href="/react-native/docs/direct-manipulation">Direct Manipulation</a></li><li class="navListItem"><a class="navItem" href="/react-native/docs/colors">Color Reference</a></li><li class="navListItem"><a class="navItem" href="/react-native/docs/integration-with-existing-apps">Integration with Existing Apps</a></li><li class="navListItem"><a class="navItem" href="/react-native/docs/building-for-apple-tv">Building For TV Devices</a></li><li class="navListItem"><a class="navItem" href="/react-native/docs/running-on-device">Running On Device</a></li><li class="navListItem"><a class="navItem" href="/react-native/docs/upgrading">Upgrading to new React Native versions</a></li><li class="navListItem"><a class="navItem" href="/react-native/docs/troubleshooting">Troubleshooting</a></li><li class="navListItem"><a class="navItem" href="/react-native/docs/native-modules-setup">Native Modules Setup</a></li><li class="navListItem"><a class="navItem" href="/react-native/docs/out-of-tree-platforms">Out-of-Tree Platforms</a></li></ul></div><div class="navGroup"><h3 class="navGroupCategoryTitle collapsible">Guides (iOS)<span class="arrow"><svg width="24" height="24" viewBox="0 0 24 24"><path fill="#565656" d="M7.41 15.41L12 10.83l4.59 4.58L18 14l-6-6-6 6z"></path><path d="M0 0h24v24H0z" fill="none"></path></svg></span></h3><ul class="hide"><li class="navListItem"><a class="navItem" href="/react-native/docs/native-modules-ios">Native Modules</a></li><li class="navListItem"><a class="navItem" href="/react-native/docs/native-components-ios">Native UI Components</a></li><li class="navListItem"><a class="navItem" href="/react-native/docs/linking-libraries-ios">Linking Libraries</a></li><li class="navListItem"><a class="navItem" href="/react-native/docs/running-on-simulator-ios">Running On Simulator</a></li><li class="navListItem"><a class="navItem" href="/react-native/docs/communication-ios">Communication between native and React Native</a></li><li class="navListItem"><a class="navItem" href="/react-native/docs/app-extensions">App Extensions</a></li></ul></div><div class="navGroup"><h3 class="navGroupCategoryTitle collapsible">Guides (Android)<span class="arrow"><svg width="24" height="24" viewBox="0 0 24 24"><path fill="#565656" d="M7.41 15.41L12 10.83l4.59 4.58L18 14l-6-6-6 6z"></path><path d="M0 0h24v24H0z" fill="none"></path></svg></span></h3><ul class="hide"><li class="navListItem"><a class="navItem" href="/react-native/docs/native-modules-android">Native Modules</a></li><li class="navListItem"><a class="navItem" href="/react-native/docs/native-components-android">Native UI Components</a></li><li class="navListItem"><a class="navItem" href="/react-native/docs/headless-js-android">Headless JS</a></li><li class="navListItem"><a class="navItem" href="/react-native/docs/signed-apk-android">Publishing to Google Play Store</a></li><li class="navListItem"><a class="navItem" href="/react-native/docs/removing-default-permissions">Removing Default Permissions</a></li><li class="navListItem"><a class="navItem" href="/react-native/docs/hermes">Enabling Hermes</a></li></ul></div></div></section></div><script>
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</script></nav></div><div class="container mainContainer"><div class="wrapper"><div class="post"><header class="postHeader"><a class="edit-page-link button" href="https://github.com/facebook/react-native-website/blob/master/docs/state.md" target="_blank" rel="noreferrer noopener">Edit</a><h1 class="postHeaderTitle">State</h1></header><article><div><span><p>There are two types of data that control a component: <code>props</code> and <code>state</code>. <code>props</code> are set by the parent and they are fixed throughout the lifetime of a component. For data that is going to change, we have to use <code>state</code>.</p>
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<p>In general, you should initialize <code>state</code> in the constructor, and then call <code>setState</code> when you want to change it.</p>
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<p>For example, let's say we want to make text that blinks all the time. The text itself gets set once when the blinking component gets created, so the text itself is a <code>prop</code>. The "whether the text is currently on or off" changes over time, so that should be kept in <code>state</code>.</p>
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<div class="web-player"><pre><code class="hljs css javascript"><span class="hljs-keyword">import</span> React, { Component } <span class="hljs-keyword">from</span> <span class="hljs-string">'react'</span>;
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<span class="hljs-keyword">import</span> { AppRegistry, Text, View } <span class="hljs-keyword">from</span> <span class="hljs-string">'react-native'</span>;
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<span class="hljs-class"><span class="hljs-keyword">class</span> <span class="hljs-title">Blink</span> <span class="hljs-keyword">extends</span> <span class="hljs-title">Component</span> </span>{
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componentDidMount(){
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<span class="hljs-comment">// Toggle the state every second</span>
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setInterval(<span class="hljs-function"><span class="hljs-params">()</span> =></span> (
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<span class="hljs-keyword">this</span>.setState(<span class="hljs-function"><span class="hljs-params">previousState</span> =></span> (
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{ <span class="hljs-attr">isShowingText</span>: !previousState.isShowingText }
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))
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), <span class="hljs-number">1000</span>);
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}
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<span class="hljs-comment">//state object</span>
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state = { <span class="hljs-attr">isShowingText</span>: <span class="hljs-literal">true</span> };
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render() {
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<span class="hljs-keyword">if</span> (!<span class="hljs-keyword">this</span>.state.isShowingText) {
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<span class="hljs-keyword">return</span> <span class="hljs-literal">null</span>;
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}
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<span class="hljs-keyword">return</span> (
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<span class="xml"><span class="hljs-tag"><<span class="hljs-name">Text</span>></span>{this.props.text}<span class="hljs-tag"></<span class="hljs-name">Text</span>></span></span>
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);
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}
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}
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<span class="hljs-keyword">export</span> <span class="hljs-keyword">default</span> <span class="hljs-class"><span class="hljs-keyword">class</span> <span class="hljs-title">BlinkApp</span> <span class="hljs-keyword">extends</span> <span class="hljs-title">Component</span> </span>{
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render() {
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<span class="hljs-keyword">return</span> (
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<View>
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<Blink text='I love to blink' />
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<Blink text='Yes blinking is so great' />
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<Blink text='Why did they ever take this out of HTML' />
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<Blink text='Look at me look at me look at me' />
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</View>
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);
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}
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}
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// skip this line if using Create React Native App
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AppRegistry.registerComponent('AwesomeProject', () => BlinkApp);
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</code></pre><iframe style="margin-top: 4" width="100%" height="420" data-src="//cdn.rawgit.com/dabbott/react-native-web-player/gh-v1.10.0/index.html#code=import%20React%2C%20%7B%20Component%20%7D%20from%20'react'%3B%0Aimport%20%7B%20AppRegistry%2C%20Text%2C%20View%20%7D%20from%20'react-native'%3B%0A%0Aclass%20Blink%20extends%20Component%20%7B%0A%0A%20%20componentDidMount()%7B%0A%20%20%20%20%2F%2F%20Toggle%20the%20state%20every%20second%0A%20%20%20%20setInterval(()%20%3D%3E%20(%0A%20%20%20%20%20%20this.setState(previousState%20%3D%3E%20(%0A%20%20%20%20%20%20%20%20%7B%20isShowingText%3A%20!previousState.isShowingText%20%7D%0A%20%20%20%20%20%20))%0A%20%20%20%20)%2C%201000)%3B%0A%20%20%7D%0A%0A%20%20%2F%2Fstate%20object%0A%20%20state%20%3D%20%7B%20isShowingText%3A%20true%20%7D%3B%0A%0A%20%20render()%20%7B%0A%20%20%20%20if%20(!this.state.isShowingText)%20%7B%0A%20%20%20%20%20%20return%20null%3B%0A%20%20%20%20%7D%0A%0A%20%20%20%20return%20(%0A%20%20%20%20%20%20%3CText%3E%7Bthis.props.text%7D%3C%2FText%3E%0A%20%20%20%20)%3B%0A%20%20%7D%0A%7D%0A%0Aexport%20default%20class%20BlinkApp%20extends%20Component%20%7B%0A%20%20render()%20%7B%0A%20%20%20%20return%20(%0A%20%20%20%20%20%20%3CView%3E%0A%20%20%20%20%20%20%20%20%3CBlink%20text%3D'I%20love%20to%20blink'%20%2F%3E%0A%20%20%20%20%20%20%20%20%3CBlink%20text%3D'Yes%20blinking%20is%20so%20great'%20%2F%3E%0A%20%20%20%20%20%20%20%20%3CBlink%20text%3D'Why%20did%20they%20ever%20take%20this%20out%20of%20HTML'%20%2F%3E%0A%20%20%20%20%20%20%20%20%3CBlink%20text%3D'Look%20at%20me%20look%20at%20me%20look%20at%20me'%20%2F%3E%0A%20%20%20%20%20%20%3C%2FView%3E%0A%20%20%20%20)%3B%0A%20%20%7D%0A%7D%0A%0A%2F%2F%20skip%20this%20line%20if%20using%20Create%20React%20Native%20App%0AAppRegistry.registerComponent('AwesomeProject'%2C%20()%20%3D%3E%20BlinkApp)%3B%0A" frame-border="0"></iframe></div>
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<p>In a real application, you probably won't be setting state with a timer. You might set state when you have new data from the server, or from user input. You can also use a state container like <a href="https://redux.js.org/">Redux</a> or <a href="https://mobx.js.org/">Mobx</a> to control your data flow. In that case you would use Redux or Mobx to modify your state rather than calling <code>setState</code> directly.</p>
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<p>When setState is called, BlinkApp will re-render its Component. By calling setState within the Timer, the component will re-render every time the Timer ticks.</p>
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<p>State works the same way as it does in React, so for more details on handling state, you can look at the <a href="https://reactjs.org/docs/react-component.html#setstate">React.Component API</a>. At this point, you might be annoyed that most of our examples so far use boring default black text. To make things more beautiful, you will have to <a href="/react-native/docs/style">learn about Style</a>.</p>
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</span></div></article></div><div class="docs-prevnext"><a class="docs-prev button" href="/react-native/docs/props"><span class="arrow-prev">← </span><span>Props</span></a><a class="docs-next button" href="/react-native/docs/style"><span>Style</span><span class="arrow-next"> →</span></a></div></div></div></div><footer class="nav-footer" id="footer"><section class="sitemap"><a href="/react-native/" class="nav-home"><img src="/react-native/img/header_logo.png" alt="React Native" width="66" height="58"/></a><div><h5><a href="/react-native/docs/getting-started.html">Docs</a></h5><a href="/react-native/docs/getting-started.html">Getting Started</a><a href="/react-native/docs/tutorial.html">Tutorial</a><a href="/react-native/docs/components-and-apis.html">Components and APIs</a><a href="/react-native/docs/more-resources.html">More Resources</a></div><div><h5>Community</h5><a href="/react-native/help.html">The React Native Community</a><a href="/react-native/showcase.html">Who's using React Native?</a><a href="http://stackoverflow.com/questions/tagged/react-native" target="_blank">Ask Questions on Stack Overflow</a><a href="https://github.com/facebook/react-native/blob/master/CONTRIBUTING.md">Contributor Guide</a></div><div><h5>More Resources</h5><a href="/react-native/blog/">Blog</a><a href="https://twitter.com/reactnative" target="_blank">Twitter</a><a href="https://github.com/facebook/react-native" target="_blank">GitHub</a><a href="http://reactjs.org" target="_blank">React</a></div></section><a href="https://code.facebook.com/projects/" target="_blank" class="fbOpenSource"><img src="/react-native/img/oss_logo.png" alt="Facebook Open Source" width="170" height="45"/></a><section class="copyright">Copyright © 2019 Facebook Inc.</section></footer></div><script type="text/javascript" src="https://cdn.jsdelivr.net/docsearch.js/1/docsearch.min.js"></script><script>window.fbAsyncInit = function() {FB.init({appId:'1677033832619985',xfbml:true,version:'v2.7'});};(function(d, s, id){var js, fjs = d.getElementsByTagName(s)[0];if (d.getElementById(id)) {return;}js = d.createElement(s); js.id = id;js.src = '//connect.facebook.net/en_US/sdk.js';fjs.parentNode.insertBefore(js, fjs);}(document, 'script','facebook-jssdk'));
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if (e.keyCode === 191) {
|
||
const search = document.getElementById('search_input_react');
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||
search && search.focus();
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}
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||
});
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||
</script><script>
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||
var search = docsearch({
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||
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||
apiKey: '2c98749b4a1e588efec53b2acec13025',
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||
indexName: 'react-native-versions',
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||
inputSelector: '#search_input_react',
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||
algoliaOptions: {"facetFilters":["tags:0.60"],"hitsPerPage":5}
|
||
});
|
||
</script></body></html> |