FlatList
A performant interface for rendering basic, 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>
.
Example
- TypeScript
- JavaScript
To render multiple columns, use the numColumns
prop. Using this approach instead of a flexWrap
layout can prevent conflicts with the item height logic.
More complex, selectable example below.
- By passing
extraData={selectedId}
toFlatList
we make sureFlatList
itself will re-render when the state changes. Without setting this prop,FlatList
would not know it needs to re-render any items because it is aPureComponent
and the prop comparison will not show any changes. keyExtractor
tells the list to use theid
s for the react keys instead of the defaultkey
property.
- TypeScript
- JavaScript
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 ifprops
remain shallow-equal. Make sure that everything yourrenderItem
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 thedata
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 customkeyExtractor
prop.
Reference
Props
VirtualizedList Props
Inherits VirtualizedList Props.
Required renderItem
renderItem({
item: ItemT,
index: number,
separators: {
highlight: () => void;
unhighlight: () => void;
updateProps: (select: 'leading' | 'trailing', newProps: any) => void;
}
}): JSX.Element;
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 |
---|
function |
item
(Object): The item fromdata
being rendered.index
(number): The index corresponding to this item in thedata
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
key={item.key}
onPress={() => this._onPress(item)}
onShowUnderlay={separators.highlight}
onHideUnderlay={separators.unhighlight}>
<View style={{backgroundColor: 'white'}}>
<Text>{item.title}</Text>
</View>
</TouchableHighlight>
)}
/>
Required data
An array (or array-like list) of items to render. Other data types can be used by targeting VirtualizedList
directly.
Type |
---|
ArrayLike |
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
. Can be a React Component (e.g. SomeComponent
), or a React element (e.g. <SomeComponent />
).
Type |
---|
component, function, element |
ListEmptyComponent
Rendered when the list is empty. Can be a React Component (e.g. SomeComponent
), or a React element (e.g. <SomeComponent />
).
Type |
---|
component, element |
ListFooterComponent
Rendered at the bottom of all the items. Can be a React Component (e.g. SomeComponent
), or a React element (e.g. <SomeComponent />
).
Type |
---|
component, element |
ListFooterComponentStyle
Styling for internal View for ListFooterComponent
.
Type |
---|
View Style |
ListHeaderComponent
Rendered at the top of all the items. Can be a React Component (e.g. SomeComponent
), or a React element (e.g. <SomeComponent />
).
Type |
---|
component, element |
ListHeaderComponentStyle
Styling for internal View for ListHeaderComponent
.
Type |
---|
View Style |
columnWrapperStyle
Optional custom style for multi-item rows generated when numColumns > 1
.
Type |
---|
View Style |
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 |
---|
any |
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 efficient 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 |
---|
function |
horizontal
If true
, renders items next to each other horizontally instead of stacked vertically.
Type |
---|
boolean |
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 | Default |
---|---|
number | 10 |
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 |
---|
number |
inverted
Reverses the direction of scroll. Uses scale transforms of -1
.
Type |
---|
boolean |
keyExtractor
(item: ItemT, 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 item.id
, and then falls back to using the index, like React does.
Type |
---|
function |
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 |
---|
number |
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 |
---|
function |
onViewableItemsChanged
Called when the viewability of rows changes, as defined by the viewabilityConfig
prop.
Type |
---|
(callback: {changed: ViewToken[], viewableItems: ViewToken[]} => void; |
progressViewOffset
Set this when offset is needed for the loading indicator to show correctly.
Type |
---|
number |
refreshing
Set this true while waiting for new data from a refresh.
Type |
---|
boolean |
removeClippedSubviews
This may improve scroll performance for large lists. On Android the default value is true
.
Note: May have bugs (missing content) in some circumstances - use at your own risk.
Type |
---|
boolean |
viewabilityConfig
See ViewabilityHelper.js
for flow type and further documentation.
Type |
---|
ViewabilityConfig |
viewabilityConfig
takes a type ViewabilityConfig
an object with following properties
Property | Type |
---|---|
minimumViewTime | number |
viewAreaCoveragePercentThreshold | number |
itemVisiblePercentThreshold | number |
waitForInteraction | 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 viewAreaCoveragePercentThreshold
, 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 |
---|
array of ViewabilityConfigCallbackPair |
Methods
flashScrollIndicators()
flashScrollIndicators();
Displays the scroll indicators momentarily.
getNativeScrollRef()
getNativeScrollRef(): React.ElementRef<typeof ScrollViewComponent>;
Provides a reference to the underlying scroll component
getScrollResponder()
getScrollResponder(): ScrollResponderMixin;
Provides a handle to the underlying scroll responder.
getScrollableNode()
getScrollableNode(): any;
Provides a handle to the underlying scroll node.
scrollToEnd()
scrollToEnd(params?: {animated?: boolean});
Scrolls to the end of the content. May be janky without getItemLayout
prop.
Parameters:
Name | Type |
---|---|
params | object |
Valid params
keys are:
- 'animated' (boolean) - Whether the list should do an animation while scrolling. Defaults to
true
.
scrollToIndex()
scrollToIndex: (params: {
index: number;
animated?: boolean;
viewOffset?: number;
viewPosition?: number;
});
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 |
---|---|
params Required | object |
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.
- 'viewPosition' (number) - A value of
0
places the item specified by index at the top,1
at the bottom, and0.5
centered in the middle.
scrollToItem()
scrollToItem(params: {
animated?: ?boolean,
item: Item,
viewPosition?: number,
});
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 |
---|---|
params Required | object |
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: {
offset: number;
animated?: boolean;
});
Scroll to a specific content pixel offset in the list.
Parameters:
Name | Type |
---|---|
params Required | object |
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
.