react-native/website/versioned_docs/0.49/flatlist.md

---
id: version-0.49-flatlist
title: flatlist
original_id: flatlist
---
<a id="content"></a><h1><a class="anchor" name="flatlist"></a>FlatList <a class="hash-link" href="docs/flatlist.html#flatlist">#</a></h1><div><div><p>A performant interface for rendering simple, flat lists, supporting the most handy features:</p><ul><li>Fully cross-platform.</li><li>Optional horizontal mode.</li><li>Configurable viewability callbacks.</li><li>Header support.</li><li>Footer support.</li><li>Separator support.</li><li>Pull to Refresh.</li><li>Scroll loading.</li><li>ScrollToIndex support.</li></ul><p>If you need section support, use <a href="docs/sectionlist.html" target="_blank"><code>&lt;SectionList&gt;</code></a>.</p><p>Minimal Example:</p><div class="prism language-javascript"><span class="token operator">&lt;</span>FlatList
  data<span class="token operator">=</span><span class="token punctuation">{</span><span class="token punctuation">[</span><span class="token punctuation">{</span>key<span class="token punctuation">:</span> <span class="token string">'a'</span><span class="token punctuation">}</span><span class="token punctuation">,</span> <span class="token punctuation">{</span>key<span class="token punctuation">:</span> <span class="token string">'b'</span><span class="token punctuation">}</span><span class="token punctuation">]</span><span class="token punctuation">}</span>
  renderItem<span class="token operator">=</span><span class="token punctuation">{</span><span class="token punctuation">(</span><span class="token punctuation">{</span>item<span class="token punctuation">}</span><span class="token punctuation">)</span> <span class="token operator">=&gt;</span> <span class="token operator">&lt;</span>Text<span class="token operator">&gt;</span><span class="token punctuation">{</span>item<span class="token punctuation">.</span>key<span class="token punctuation">}</span><span class="token operator">&lt;</span><span class="token operator">/</span>Text<span class="token operator">&gt;</span><span class="token punctuation">}</span>
<span class="token operator">/</span><span class="token operator">&gt;</span></div><p>More complex example demonstrating <code>PureComponent</code> usage for perf optimization and avoiding bugs.</p><ul><li>By binding the <code>onPressItem</code> handler, the props will remain <code>===</code> and <code>PureComponent</code> will
prevent wasteful re-renders unless the actual <code>id</code>, <code>selected</code>, or <code>title</code> props change, even
if the inner <code>SomeOtherWidget</code> has no such optimizations.</li><li>By passing <code>extraData={this.state}</code> to <code>FlatList</code> we make sure <code>FlatList</code> itself will re-render
when the <code>state.selected</code> changes. Without setting this prop, <code>FlatList</code> would not know it
needs to re-render any items because it is also a <code>PureComponent</code> and the prop comparison will
not show any changes.</li><li><code>keyExtractor</code> tells the list to use the <code>id</code>s for the react keys.</li></ul><div class="prism language-javascript"><span class="token keyword">class</span> <span class="token class-name">MyListItem</span> <span class="token keyword">extends</span> <span class="token class-name">React<span class="token punctuation">.</span>PureComponent</span> <span class="token punctuation">{</span>
  _onPress <span class="token operator">=</span> <span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token operator">=&gt;</span> <span class="token punctuation">{</span>
    <span class="token keyword">this</span><span class="token punctuation">.</span>props<span class="token punctuation">.</span><span class="token function">onPressItem</span><span class="token punctuation">(</span><span class="token keyword">this</span><span class="token punctuation">.</span>props<span class="token punctuation">.</span>id<span class="token punctuation">)</span><span class="token punctuation">;</span>
  <span class="token punctuation">}</span><span class="token punctuation">;</span>

  <span class="token function">render</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
    <span class="token keyword">return</span> <span class="token punctuation">(</span>
      <span class="token operator">&lt;</span>SomeOtherWidget
        <span class="token punctuation">{</span><span class="token operator">...</span><span class="token keyword">this</span><span class="token punctuation">.</span>props<span class="token punctuation">}</span>
        onPress<span class="token operator">=</span><span class="token punctuation">{</span><span class="token keyword">this</span><span class="token punctuation">.</span>_onPress<span class="token punctuation">}</span>
      <span class="token operator">/</span><span class="token operator">&gt;</span>
    <span class="token punctuation">)</span>
  <span class="token punctuation">}</span>
<span class="token punctuation">}</span>

<span class="token keyword">class</span> <span class="token class-name">MyList</span> <span class="token keyword">extends</span> <span class="token class-name">React<span class="token punctuation">.</span>PureComponent</span> <span class="token punctuation">{</span>
  state <span class="token operator">=</span> <span class="token punctuation">{</span>selected<span class="token punctuation">:</span> <span class="token punctuation">(</span><span class="token keyword">new</span> <span class="token class-name">Map</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">:</span> Map<span class="token operator">&lt;</span>string<span class="token punctuation">,</span> boolean<span class="token operator">&gt;</span><span class="token punctuation">)</span><span class="token punctuation">}</span><span class="token punctuation">;</span>

  _keyExtractor <span class="token operator">=</span> <span class="token punctuation">(</span>item<span class="token punctuation">,</span> index<span class="token punctuation">)</span> <span class="token operator">=&gt;</span> item<span class="token punctuation">.</span>id<span class="token punctuation">;</span>

  _onPressItem <span class="token operator">=</span> <span class="token punctuation">(</span>id<span class="token punctuation">:</span> string<span class="token punctuation">)</span> <span class="token operator">=&gt;</span> <span class="token punctuation">{</span>
   <span class="token comment" spellcheck="true"> // updater functions are preferred for transactional updates
</span>    <span class="token keyword">this</span><span class="token punctuation">.</span><span class="token function">setState</span><span class="token punctuation">(</span><span class="token punctuation">(</span>state<span class="token punctuation">)</span> <span class="token operator">=&gt;</span> <span class="token punctuation">{</span>
     <span class="token comment" spellcheck="true"> // copy the map rather than modifying state.
</span>      <span class="token keyword">const</span> selected <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">Map</span><span class="token punctuation">(</span>state<span class="token punctuation">.</span>selected<span class="token punctuation">)</span><span class="token punctuation">;</span>
      selected<span class="token punctuation">.</span><span class="token keyword">set</span><span class="token punctuation">(</span>id<span class="token punctuation">,</span> <span class="token operator">!</span>selected<span class="token punctuation">.</span><span class="token keyword">get</span><span class="token punctuation">(</span>id<span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span><span class="token comment" spellcheck="true"> // toggle
</span>      <span class="token keyword">return</span> <span class="token punctuation">{</span>selected<span class="token punctuation">}</span><span class="token punctuation">;</span>
    <span class="token punctuation">}</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
  <span class="token punctuation">}</span><span class="token punctuation">;</span>

  _renderItem <span class="token operator">=</span> <span class="token punctuation">(</span><span class="token punctuation">{</span>item<span class="token punctuation">}</span><span class="token punctuation">)</span> <span class="token operator">=&gt;</span> <span class="token punctuation">(</span>
    <span class="token operator">&lt;</span>MyListItem
      id<span class="token operator">=</span><span class="token punctuation">{</span>item<span class="token punctuation">.</span>id<span class="token punctuation">}</span>
      onPressItem<span class="token operator">=</span><span class="token punctuation">{</span><span class="token keyword">this</span><span class="token punctuation">.</span>_onPressItem<span class="token punctuation">}</span>
      selected<span class="token operator">=</span><span class="token punctuation">{</span><span class="token operator">!</span><span class="token operator">!</span><span class="token keyword">this</span><span class="token punctuation">.</span>state<span class="token punctuation">.</span>selected<span class="token punctuation">.</span><span class="token keyword">get</span><span class="token punctuation">(</span>item<span class="token punctuation">.</span>id<span class="token punctuation">)</span><span class="token punctuation">}</span>
      title<span class="token operator">=</span><span class="token punctuation">{</span>item<span class="token punctuation">.</span>title<span class="token punctuation">}</span>
    <span class="token operator">/</span><span class="token operator">&gt;</span>
  <span class="token punctuation">)</span><span class="token punctuation">;</span>

  <span class="token function">render</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
    <span class="token keyword">return</span> <span class="token punctuation">(</span>
      <span class="token operator">&lt;</span>FlatList
        data<span class="token operator">=</span><span class="token punctuation">{</span><span class="token keyword">this</span><span class="token punctuation">.</span>props<span class="token punctuation">.</span>data<span class="token punctuation">}</span>
        extraData<span class="token operator">=</span><span class="token punctuation">{</span><span class="token keyword">this</span><span class="token punctuation">.</span>state<span class="token punctuation">}</span>
        keyExtractor<span class="token operator">=</span><span class="token punctuation">{</span><span class="token keyword">this</span><span class="token punctuation">.</span>_keyExtractor<span class="token punctuation">}</span>
        renderItem<span class="token operator">=</span><span class="token punctuation">{</span><span class="token keyword">this</span><span class="token punctuation">.</span>_renderItem<span class="token punctuation">}</span>
      <span class="token operator">/</span><span class="token operator">&gt;</span>
    <span class="token punctuation">)</span><span class="token punctuation">;</span>
  <span class="token punctuation">}</span>
<span class="token punctuation">}</span></div><p>This is a convenience wrapper around <a href="docs/virtualizedlist.html" target="_blank"><code>&lt;VirtualizedList&gt;</code></a>,
and thus inherits its props (as well as those of <code>ScrollView</code>) that aren't explicitly listed
here, along with the following caveats:</p><ul><li>Internal state is not preserved when content scrolls out of the render window. Make sure all
your data is captured in the item data or external stores like Flux, Redux, or Relay.</li><li>This is a <code>PureComponent</code> which means that it will not re-render if <code>props</code> remain shallow-
equal. Make sure that everything your <code>renderItem</code> function depends on is passed as a prop
(e.g. <code>extraData</code>) that is not <code>===</code> after updates, otherwise your UI may not update on
changes. This includes the <code>data</code> prop and parent component state.</li><li>In order to constrain memory and enable smooth scrolling, content is rendered asynchronously
offscreen. This means it's possible to scroll faster than the fill rate ands momentarily see
blank content. This is a tradeoff that can be adjusted to suit the needs of each application,
and we are working on improving it behind the scenes.</li><li>By default, the list looks for a <code>key</code> prop on each item and uses that for the React key.
Alternatively, you can provide a custom <code>keyExtractor</code> prop.</li></ul><p>Also inherets <a href="docs/scrollview.html#props" target="_blank">ScrollView Props</a>, unless it is nested in another FlatList of same orientation.</p></div><h3><a class="anchor" name="props"></a>Props <a class="hash-link" href="docs/flatlist.html#props">#</a></h3><div class="props"><div class="prop"><h4 class="propTitle"><a class="anchor" name="numcolumns"></a>numColumns?:  <a class="hash-link" href="docs/flatlist.html#numcolumns">#</a></h4></div></div><span><h3><a class="anchor" name="methods"></a>Methods <a class="hash-link" href="docs/flatlist.html#methods">#</a></h3><div class="props"><div class="prop"><h4 class="methodTitle"><a class="anchor" name="scrolltoend"></a>scrollToEnd<span class="methodType">(params?: object)</span> <a class="hash-link" href="docs/flatlist.html#scrolltoend">#</a></h4><div><p>Scrolls to the end of the content. May be janky without <code>getItemLayout</code> prop.</p></div></div><div class="prop"><h4 class="methodTitle"><a class="anchor" name="scrolltoindex"></a>scrollToIndex<span class="methodType">(params: object)</span> <a class="hash-link" href="docs/flatlist.html#scrolltoindex">#</a></h4><div><p>Scrolls to the item at the specified index such that it is positioned in the viewable area
such that <code>viewPosition</code> 0 places it at the top, 1 at the bottom, and 0.5 centered in the
middle. <code>viewOffset</code> is a fixed number of pixels to offset the final target position.</p><p>Note: cannot scroll to locations outside the render window without specifying the
<code>getItemLayout</code> prop.</p></div></div><div class="prop"><h4 class="methodTitle"><a class="anchor" name="scrolltoitem"></a>scrollToItem<span class="methodType">(params: object)</span> <a class="hash-link" href="docs/flatlist.html#scrolltoitem">#</a></h4><div><p>Requires linear scan through data - use <code>scrollToIndex</code> instead if possible.</p><p>Note: cannot scroll to locations outside the render window without specifying the
<code>getItemLayout</code> prop.</p></div></div><div class="prop"><h4 class="methodTitle"><a class="anchor" name="scrolltooffset"></a>scrollToOffset<span class="methodType">(params: object)</span> <a class="hash-link" href="docs/flatlist.html#scrolltooffset">#</a></h4><div><p>Scroll to a specific content pixel offset in the list.</p><p>Check out <a href="docs/virtualizedlist.html#scrolltooffset" target="_blank">scrollToOffset</a> of VirtualizedList</p></div></div><div class="prop"><h4 class="methodTitle"><a class="anchor" name="recordinteraction"></a>recordInteraction<span class="methodType">()</span> <a class="hash-link" href="docs/flatlist.html#recordinteraction">#</a></h4><div><p>Tells the list an interaction has occured, which should trigger viewability calculations, e.g.
if <code>waitForInteractions</code> is true and the user has not scrolled. This is typically called by
taps on items or by navigation actions.</p></div></div><div class="prop"><h4 class="methodTitle"><a class="anchor" name="flashscrollindicators"></a>flashScrollIndicators<span class="methodType">()</span> <a class="hash-link" href="docs/flatlist.html#flashscrollindicators">#</a></h4><div><p>Displays the scroll indicators momentarily.</p></div></div></div></span></div><p class="edit-page-block"><a target="_blank" href="https://github.com/facebook/react-native/blob/master/Libraries/Lists/FlatList.js">Improve this page</a> by sending a pull request!</p><div class="docs-prevnext"><a class="docs-prev" href="docs/drawerlayoutandroid.html#content">← Prev</a><a class="docs-next" href="docs/image.html#content">Next →</a></div>