Documentation

SDK33

FlatList

A performant interface for rendering simple, flat lists, supporting the most handy features:

Fully cross-platform.
Optional horizontal mode.
Configurable viewability callbacks.
Header support.
Footer support.
Separator support.
Pull to Refresh.
Scroll loading.
ScrollToIndex support.
Multiple column support.

If you need section support, use <SectionList>.

Minimal Example:

```javascript

<FlatList
  data={[{key: 'a'}, {key: 'b'}]}
  renderItem={({item}) => <Text>{item.key}</Text>}
/>

```javascript


To render multiple columns, use the [`numColumns`](../flatlist/#numcolumns) prop. Using this approach instead of a `flexWrap` layout can prevent conflicts with the item height logic.

More complex, multi-select example demonstrating PureComponent usage for perf optimization and avoiding bugs.

By binding the onPressItem handler, the props will remain === and PureComponent will prevent wasteful re-renders unless the actual id, selected, or title props change, even if the components rendered in MyListItem did not have such optimizations.
By passing extraData={this.state} to FlatList we make sure FlatList itself will re-render when the state.selected changes. Without setting this prop, FlatList would not know it needs to re-render any items because it is also a PureComponent and the prop comparison will not show any changes.
keyExtractor tells the list to use the ids for the react keys instead of the default key property.

```javascript
class MyListItem extends React.PureComponent {
  _onPress = () => {
    this.props.onPressItem(this.props.id);
  };

  render() {
    const textColor = this.props.selected ? 'red' : 'black';
    return (
      <TouchableOpacity onPress={this._onPress}>
        <View>
          <Text style={{color: textColor}}>{this.props.title}</Text>
        </View>
      </TouchableOpacity>
    );
  }
}

class MultiSelectList extends React.PureComponent {
  state = {selected: (new Map(): Map<string, boolean>)};

  _keyExtractor = (item, index) => item.id;

  _onPressItem = (id: string) => {
    // updater functions are preferred for transactional updates
    this.setState((state) => {
      // copy the map rather than modifying state.
      const selected = new Map(state.selected);
      selected.set(id, !selected.get(id)); // toggle
      return {selected};
    });
  };

  _renderItem = ({item}) => (
    <MyListItem
      id={item.id}
      onPressItem={this._onPressItem}
      selected={!!this.state.selected.get(item.id)}
      title={item.title}
    />
  );

  render() {
    return (
      <FlatList
        data={this.props.data}
        extraData={this.state}
        keyExtractor={this._keyExtractor}
        renderItem={this._renderItem}
      />
    );
  }
}

This is a convenience wrapper around [``](../virtualizedlist/), and thus inherits its props (as well as those of [``](../scrollview/)) that aren't explicitly listed here, along with the following caveats:

- 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.
- This is a `PureComponent` which means that it will not re-render if `props` remain shallow-equal. Make sure that everything your `renderItem` function depends on is passed as a prop (e.g. `extraData`) that is not `===` after updates, otherwise your UI may not update on changes. This includes the `data` prop and parent component state.
- 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 and 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.
- By default, the list looks for a `key` prop on each item and uses that for the React key. Alternatively, you can provide a custom `keyExtractor` prop.

Also inherits [ScrollView Props](../scrollview/#props), unless it is nested in another FlatList of same orientation.

### Props

- [`columnWrapperStyle`](../flatlist/#columnwrapperstyle)
- [`data`](../flatlist/#data)
- [`extraData`](../flatlist/#extradata)
- [`getItemLayout`](../flatlist/#getitemlayout)
- [`horizontal`](../flatlist/#horizontal)
- [`initialNumToRender`](../flatlist/#initialnumtorender)
- [`initialScrollIndex`](../flatlist/#initialscrollindex)
- [`inverted`](../flatlist/#inverted)
- [`ItemSeparatorComponent`](../flatlist/#itemseparatorcomponent)
- [`keyExtractor`](../flatlist/#keyextractor)
- [`legacyImplementation`](../flatlist/#legacyimplementation)
- [`ListEmptyComponent`](../flatlist/#listemptycomponent)
- [`ListFooterComponent`](../flatlist/#listfootercomponent)
- [`ListFooterComponentStyle`](../flatlist/#listfootercomponentstyle)
- [`ListHeaderComponent`](../flatlist/#listheadercomponent)
- [`ListHeaderComponentStyle`](../flatlist/#listheadercomponentstyle)
- [`numColumns`](../flatlist/#numcolumns)
- [`onEndReached`](../flatlist/#onendreached)
- [`onEndReachedThreshold`](../flatlist/#onendreachedthreshold)
- [`onRefresh`](../flatlist/#onrefresh)
- [`onViewableItemsChanged`](../flatlist/#onviewableitemschanged)
- [`progressViewOffset`](../flatlist/#progressviewoffset)
- [`refreshing`](../flatlist/#refreshing)
- [`renderItem`](../flatlist/#renderitem)
- [`removeClippedSubviews`](../flatlist/#removeclippedsubviews)
- [`ScrollView` props...](../scrollview/#props)
- [`viewabilityConfig`](../flatlist/#viewabilityconfig)
- [`viewabilityConfigCallbackPairs`](../flatlist/#viewabilityconfigcallbackpairs)
- [`VirtualizedList` props...](../virtualizedlist/#props)

### Methods

- [`flashScrollIndicators`](../flatlist/#flashscrollindicators)
- [`getScrollResponder`](../flatlist/#getScrollResponder)
- [`getScrollableNode`](../flatlist/#getScrollableNode)
- [`scrollToEnd`](../flatlist/#scrolltoend)
- [`scrollToIndex`](../flatlist/#scrolltoindex)
- [`scrollToItem`](../flatlist/#scrolltoitem)
- [`scrollToOffset`](../flatlist/#scrolltooffset)
- [`recordInteraction`](../flatlist/#recordinteraction)

---

# Reference

## Props

### `renderItem`


```javascript

renderItem({item, index, separators});

Takes an item from data and renders it into the list.

Provides additional metadata like index if you need it, as well as a more generic separators.updateProps function which let you set whatever props you want to change the rendering of either the leading separator or trailing separator in case the more common highlight and unhighlight (which set the highlighted: boolean prop) are insufficient for your use case.

Type	Required
function	Yes

item (Object): The item from data being rendered.
index (number): The index corresponding to this item in the data array.
separators (Object)
- highlight (Function)
- unhighlight (Function)
- updateProps (Function)
  - select (enum('leading', 'trailing'))
  - newProps (Object)

Example usage:

<FlatList
  ItemSeparatorComponent={Platform.OS !== 'android' && ({highlighted}) => (
    <View style={[style.separator, highlighted && {marginLeft: 0}]} />
  )}
  data={[{title: 'Title Text', key: 'item1'}]}
  renderItem={({item, index, separators}) => (
    <TouchableHighlight
      onPress={() => this._onPress(item)}
      onShowUnderlay={separators.highlight}
      onHideUnderlay={separators.unhighlight}>
      <View style={{backgroundColor: 'white'}}>
        <Text>{item.title}</Text>
      </View>
    </TouchableHighlight>
  )}
/>

`data`

For simplicity, data is just a plain array. If you want to use something else, like an immutable list, use the underlying VirtualizedList directly.

Type	Required
array	Yes

`ItemSeparatorComponent`

Rendered in between each item, but not at the top or bottom. By default, highlighted and leadingItem props are provided. renderItem provides separators.highlight/unhighlight which will update the highlighted prop, but you can also add custom props with separators.updateProps.

Type	Required
component	No

`ListEmptyComponent`

Rendered when the list is empty. Can be a React Component Class, a render function, or a rendered element.

Type	Required
component, function, element	No

`ListFooterComponent`

Rendered at the bottom of all the items. Can be a React Component Class, a render function, or a rendered element.

Type	Required
component, function, element	No

`ListFooterComponentStyle`

Styling for internal View for ListFooterComponent

Type	Required
style object	No

`ListHeaderComponent`

Rendered at the top of all the items. Can be a React Component Class, a render function, or a rendered element.

Type	Required
component, function, element	No

`ListHeaderComponentStyle`

Styling for internal View for ListHeaderComponent

Type	Required
style object	No

`columnWrapperStyle`

Optional custom style for multi-item rows generated when numColumns > 1.

Type	Required
style object	No

`extraData`

A marker property for telling the list to re-render (since it implements PureComponent). If any of your renderItem, Header, Footer, etc. functions depend on anything outside of the data prop, stick it here and treat it immutably.

Type	Required
any	No

`getItemLayout`

(data, index) => {length: number, offset: number, index: number}

getItemLayout is an optional optimization that allows skipping the measurement of dynamic content if you know the size (height or width) of items ahead of time. getItemLayout is both efficient and easy to use if you have fixed size items, for example:

  getItemLayout={(data, index) => (
    {length: ITEM_HEIGHT, offset: ITEM_HEIGHT * index, index}
  )}

Adding getItemLayout can be a great performance boost for lists of several hundred items. Remember to include separator length (height or width) in your offset calculation if you specify ItemSeparatorComponent.

Type	Required
function	No

`horizontal`

If true, renders items next to each other horizontally instead of stacked vertically.

Type	Required
boolean	No

`initialNumToRender`

How many items to render in the initial batch. This should be enough to fill the screen but not much more. Note these items will never be unmounted as part of the windowed rendering in order to improve perceived performance of scroll-to-top actions.

Type	Required
number	No

`initialScrollIndex`

Instead of starting at the top with the first item, start at initialScrollIndex. This disables the "scroll to top" optimization that keeps the first initialNumToRender items always rendered and immediately renders the items starting at this initial index. Requires getItemLayout to be implemented.

Type	Required
number	No

`inverted`

Reverses the direction of scroll. Uses scale transforms of -1.

Type	Required
boolean	No

`keyExtractor`

(item: object, index: number) => string;

Used to extract a unique key for a given item at the specified index. Key is used for caching and as the react key to track item re-ordering. The default extractor checks item.key, then falls back to using the index, like React does.

Type	Required
function	No

`numColumns`

Multiple columns can only be rendered with horizontal={false} and will zig-zag like a flexWrap layout. Items should all be the same height - masonry layouts are not supported.

Type	Required
number	No

`onEndReached`

(info: {distanceFromEnd: number}) => void

Called once when the scroll position gets within onEndReachedThreshold of the rendered content.

Type	Required
function	No

`onEndReachedThreshold`

How far from the end (in units of visible length of the list) the bottom edge of the list must be from the end of the content to trigger the onEndReached callback. Thus a value of 0.5 will trigger onEndReached when the end of the content is within half the visible length of the list.

Type	Required
number	No

`onRefresh`

() => void

If provided, a standard RefreshControl will be added for "Pull to Refresh" functionality. Make sure to also set the refreshing prop correctly.

Type	Required
function	No

`onViewableItemsChanged`

(info: {
    viewableItems: array,
    changed: array,
  }) => void

Called when the viewability of rows changes, as defined by the viewabilityConfig prop.

Type	Required
function	No

`progressViewOffset`

Set this when offset is needed for the loading indicator to show correctly.

Type	Required	Platform
number	No	Android

`legacyImplementation`

May not have full feature parity and is meant for debugging and performance comparison.

Type	Required
boolean	No

`refreshing`

Set this true while waiting for new data from a refresh.

Type	Required
boolean	No

`removeClippedSubviews`

This may improve scroll performance for large lists.

Note: May have bugs (missing content) in some circumstances - use at your own risk.

Type	Required
boolean	No

`viewabilityConfig`

See ViewabilityHelper.js for flow type and further documentation.

Type	Required
ViewabilityConfig	No

viewabilityConfig takes a type ViewabilityConfig an object with following properties

Property	Required	Type
minimumViewTime	No	number
viewAreaCoveragePercentThreshold	No	number
itemVisiblePercentThreshold	No	number
waitForInteraction	No	boolean

At least one of the viewAreaCoveragePercentThreshold or itemVisiblePercentThreshold is required. This needs to be done in the constructor to avoid following error (ref):

  Error: Changing viewabilityConfig on the fly is not supported`

constructor (props) {
  super(props)

  this.viewabilityConfig = {
      waitForInteraction: true,
      viewAreaCoveragePercentThreshold: 95
  }
}

<FlatList
    viewabilityConfig={this.viewabilityConfig}
  ...

minimumViewTime

Minimum amount of time (in milliseconds) that an item must be physically viewable before the viewability callback will be fired. A high number means that scrolling through content without stopping will not mark the content as viewable.

viewAreaCoveragePercentThreshold

Percent of viewport that must be covered for a partially occluded item to count as "viewable", 0-100. Fully visible items are always considered viewable. A value of 0 means that a single pixel in the viewport makes the item viewable, and a value of 100 means that an item must be either entirely visible or cover the entire viewport to count as viewable.

itemVisiblePercentThreshold

Similar to viewAreaPercentThreshold, but considers the percent of the item that is visible, rather than the fraction of the viewable area it covers.

waitForInteraction

Nothing is considered viewable until the user scrolls or recordInteraction is called after render.

`viewabilityConfigCallbackPairs`

List of ViewabilityConfig/onViewableItemsChanged pairs. A specific onViewableItemsChanged will be called when its corresponding ViewabilityConfig's conditions are met. See ViewabilityHelper.js for flow type and further documentation.

Type	Required
array of ViewabilityConfigCallbackPair	No

Methods

`scrollToEnd()`

scrollToEnd([params]);

Scrolls to the end of the content. May be janky without getItemLayout prop.

Parameters:

Name	Type	Required	Description
params	object	No	See below.

Valid params keys are:

'animated' (boolean) - Whether the list should do an animation while scrolling. Defaults to true.

`scrollToIndex()`

scrollToIndex(params);

Scrolls to the item at the specified index such that it is positioned in the viewable area such that viewPosition 0 places it at the top, 1 at the bottom, and 0.5 centered in the middle.

Note: Cannot scroll to locations outside the render window without specifying the getItemLayout prop.

Parameters:

Name	Type	Required	Description
params	object	Yes	See below.

Valid params keys are:

'animated' (boolean) - Whether the list should do an animation while scrolling. Defaults to true.
'index' (number) - The index to scroll to. Required.
'viewOffset' (number) - A fixed number of pixels to offset the final target position. Required.
'viewPosition' (number) - A value of 0 places the item specified by index at the top, 1 at the bottom, and 0.5 centered in the middle.

`scrollToItem()`

scrollToItem(params);

Requires linear scan through data - use scrollToIndex instead if possible.

Note: Cannot scroll to locations outside the render window without specifying the getItemLayout prop.

Parameters:

Name	Type	Required	Description
params	object	Yes	See below.

Valid params keys are:

'animated' (boolean) - Whether the list should do an animation while scrolling. Defaults to true.
'item' (object) - The item to scroll to. Required.
'viewPosition' (number)

`scrollToOffset()`

scrollToOffset(params);

Scroll to a specific content pixel offset in the list.

Parameters:

Name	Type	Required	Description
params	object	Yes	See below.

Valid params keys are:

'offset' (number) - The offset to scroll to. In case of horizontal being true, the offset is the x-value, in any other case the offset is the y-value. Required.
'animated' (boolean) - Whether the list should do an animation while scrolling. Defaults to true.

`recordInteraction()`

recordInteraction();

Tells the list an interaction has occurred, which should trigger viewability calculations, e.g. if waitForInteractions is true and the user has not scrolled. This is typically called by taps on items or by navigation actions.

`flashScrollIndicators()`

flashScrollIndicators();

Displays the scroll indicators momentarily.

`getScrollResponder()`

getScrollResponder();

Provides a handle to the underlying scroll responder.

`getScrollableNode()`

getScrollableNode();

Provides a handle to the underlying scroll node.

FlatList

Permalinkdata

PermalinkItemSeparatorComponent

PermalinkListEmptyComponent

PermalinkListFooterComponent

PermalinkListFooterComponentStyle

PermalinkListHeaderComponent

PermalinkListHeaderComponentStyle

PermalinkcolumnWrapperStyle

PermalinkextraData

PermalinkgetItemLayout

Permalinkhorizontal

PermalinkinitialNumToRender

PermalinkinitialScrollIndex

Permalinkinverted

PermalinkkeyExtractor

PermalinknumColumns

PermalinkonEndReached

PermalinkonEndReachedThreshold

PermalinkonRefresh

PermalinkonViewableItemsChanged

PermalinkprogressViewOffset

PermalinklegacyImplementation

Permalinkrefreshing

PermalinkremoveClippedSubviews

PermalinkviewabilityConfig

PermalinkminimumViewTime

PermalinkviewAreaCoveragePercentThreshold

PermalinkitemVisiblePercentThreshold

PermalinkwaitForInteraction

PermalinkviewabilityConfigCallbackPairs

PermalinkMethods

PermalinkscrollToEnd()

PermalinkscrollToIndex()

PermalinkscrollToItem()

PermalinkscrollToOffset()

PermalinkrecordInteraction()

PermalinkflashScrollIndicators()

PermalinkgetScrollResponder()

PermalinkgetScrollableNode()

`data`

`ItemSeparatorComponent`

`ListEmptyComponent`

`ListFooterComponent`

`ListFooterComponentStyle`

`ListHeaderComponent`

`ListHeaderComponentStyle`

`columnWrapperStyle`

`extraData`

`getItemLayout`

`horizontal`

`initialNumToRender`

`initialScrollIndex`

`inverted`

`keyExtractor`

`numColumns`

`onEndReached`

`onEndReachedThreshold`

`onRefresh`

`onViewableItemsChanged`

`progressViewOffset`

`legacyImplementation`

`refreshing`

`removeClippedSubviews`

`viewabilityConfig`

minimumViewTime

viewAreaCoveragePercentThreshold

itemVisiblePercentThreshold

waitForInteraction

`viewabilityConfigCallbackPairs`

Methods

`scrollToEnd()`

`scrollToIndex()`

`scrollToItem()`

`scrollToOffset()`

`recordInteraction()`

`flashScrollIndicators()`

`getScrollResponder()`

`getScrollableNode()`