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VirtualizedList

Base implementation for the more convenient <FlatList> and <SectionList> components, which are also better documented. In general, this should only really be used if you need more flexibility than FlatList provides, e.g. for use with immutable data instead of plain arrays.

Virtualization massively improves memory consumption and performance of large lists by maintaining a finite render window of active items and replacing all items outside of the render window with appropriately sized blank space. The window adapts to scrolling behavior, and items are rendered incrementally with low-pri (after any running interactions) if they are far from the visible area, or with hi-pri otherwise to minimize the potential of seeing blank space.

Some 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 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.
• 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.

Props

• last
• first
• horizontal
• initialNumToRender
• keyExtractor
• disableVirtualization
• maxToRenderPerBatch
• onEndReachedThreshold
• scrollEventThrottle
• updateCellsBatchingPeriod
• windowSize

Methods

• scrollToEnd
• scrollToIndex
• scrollToItem
• scrollToOffset
• recordInteraction
• flashScrollIndicators

Type Definitions

• renderItemType

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Reference

Props

last

Type	Required
number	Yes

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first

Type	Required
number	Yes

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horizontal

Type	Required
	No

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initialNumToRender

Type	Required
	No

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keyExtractor

Type	Required
	No

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disableVirtualization

Type	Required
	No

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maxToRenderPerBatch

Type	Required
	No

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onEndReachedThreshold

Type	Required
	No

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scrollEventThrottle

Type	Required
	No

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updateCellsBatchingPeriod

Type	Required
	No

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windowSize

Type	Required
	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.

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scrollToIndex()

scrollToIndex(params);

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.

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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)

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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.

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recordInteraction()

recordInteraction();

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flashScrollIndicators()

flashScrollIndicators();

Type Definitions

renderItemType

A renderItem function that takes an object and returns a React element.

Type
function