500 lines
18 KiB
JavaScript
500 lines
18 KiB
JavaScript
/**
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* Copyright (c) 2015-present, Facebook, Inc.
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* All rights reserved.
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*
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* This source code is licensed under the BSD-style license found in the
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* LICENSE file in the root directory of this source tree. An additional grant
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* of patent rights can be found in the PATENTS file in the same directory.
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*
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* @providesModule FlatList
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* @flow
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*/
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'use strict';
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const MetroListView = require('MetroListView'); // Used as a fallback legacy option
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const React = require('React');
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const View = require('View');
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const VirtualizedList = require('VirtualizedList');
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const invariant = require('fbjs/lib/invariant');
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import type {StyleObj} from 'StyleSheetTypes';
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import type {ViewabilityConfig, ViewToken} from 'ViewabilityHelper';
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import type {Props as VirtualizedListProps} from 'VirtualizedList';
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type RequiredProps<ItemT> = {
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/**
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* Takes an item from `data` and renders it into the list. Example usage:
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*
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* <FlatList
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* ItemSeparatorComponent={Platform.OS !== 'android' && ({highlighted}) => (
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* <View style={[style.separator, highlighted && {marginLeft: 0}]} />
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* )}
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* data={[{title: 'Title Text', key: 'item1'}]}
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* renderItem={({item, separators}) => (
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* <TouchableHighlight
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* onPress={() => this._onPress(item)}
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* onShowUnderlay={separators.highlight}
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* onHideUnderlay={separators.unhighlight}>
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* <View style={{backgroundColor: 'white'}}>
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* <Text>{item.title}}</Text>
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* </View>
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* </TouchableHighlight>
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* )}
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* />
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*
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* Provides additional metadata like `index` if you need it, as well as a more generic
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* `separators.updateProps` function which let's you set whatever props you want to change the
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* rendering of either the leading separator or trailing separator in case the more common
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* `highlight` and `unhighlight` (which set the `highlighted: boolean` prop) are insufficient for
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* your use-case.
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*/
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renderItem: (info: {
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item: ItemT,
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index: number,
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separators: {
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highlight: () => void,
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unhighlight: () => void,
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updateProps: (select: 'leading' | 'trailing', newProps: Object) => void,
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},
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}) => ?React.Element<any>,
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/**
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* For simplicity, data is just a plain array. If you want to use something else, like an
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* immutable list, use the underlying `VirtualizedList` directly.
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*/
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data: ?$ReadOnlyArray<ItemT>,
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};
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type OptionalProps<ItemT> = {
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/**
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* Rendered in between each item, but not at the top or bottom. By default, `highlighted` and
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* `leadingItem` props are provided. `renderItem` provides `separators.highlight`/`unhighlight`
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* which will update the `highlighted` prop, but you can also add custom props with
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* `separators.updateProps`.
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*/
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ItemSeparatorComponent?: ?ReactClass<any>,
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/**
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* Rendered at the bottom of all the items. Can be a React Component Class, a render function, or
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* a rendered element.
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*/
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ListFooterComponent?: ?(ReactClass<any> | React.Element<any>),
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/**
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* Rendered at the top of all the items. Can be a React Component Class, a render function, or
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* a rendered element.
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*/
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ListHeaderComponent?: ?(ReactClass<any> | React.Element<any>),
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/**
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* Optional custom style for multi-item rows generated when numColumns > 1.
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*/
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columnWrapperStyle?: StyleObj,
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/**
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* A marker property for telling the list to re-render (since it implements `PureComponent`). If
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* any of your `renderItem`, Header, Footer, etc. functions depend on anything outside of the
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* `data` prop, stick it here and treat it immutably.
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*/
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extraData?: any,
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/**
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* `getItemLayout` is an optional optimizations that let us skip measurement of dynamic content if
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* you know the height of items a priori. `getItemLayout` is the most efficient, and is easy to
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* use if you have fixed height items, for example:
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*
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* getItemLayout={(data, index) => (
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* {length: ITEM_HEIGHT, offset: ITEM_HEIGHT * index, index}
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* )}
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*
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* Remember to include separator length (height or width) in your offset calculation if you
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* specify `ItemSeparatorComponent`.
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*/
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getItemLayout?: (data: ?Array<ItemT>, index: number) =>
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{length: number, offset: number, index: number},
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/**
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* If true, renders items next to each other horizontally instead of stacked vertically.
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*/
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horizontal?: ?boolean,
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/**
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* How many items to render in the initial batch. This should be enough to fill the screen but not
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* much more. Note these items will never be unmounted as part of the windowed rendering in order
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* to improve perceived performance of scroll-to-top actions.
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*/
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initialNumToRender: number,
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/**
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* Instead of starting at the top with the first item, start at `initialScrollIndex`. This
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* disables the "scroll to top" optimization that keeps the first `initialNumToRender` items
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* always rendered and immediately renders the items starting at this initial index. Requires
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* `getItemLayout` to be implemented.
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*/
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initialScrollIndex?: ?number,
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/**
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* Used to extract a unique key for a given item at the specified index. Key is used for caching
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* and as the react key to track item re-ordering. The default extractor checks `item.key`, then
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* falls back to using the index, like React does.
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*/
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keyExtractor: (item: ItemT, index: number) => string,
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/**
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* Multiple columns can only be rendered with `horizontal={false}` and will zig-zag like a
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* `flexWrap` layout. Items should all be the same height - masonry layouts are not supported.
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*/
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numColumns: number,
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/**
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* Called once when the scroll position gets within `onEndReachedThreshold` of the rendered
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* content.
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*/
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onEndReached?: ?(info: {distanceFromEnd: number}) => void,
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/**
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* How far from the end (in units of visible length of the list) the bottom edge of the
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* list must be from the end of the content to trigger the `onEndReached` callback.
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* Thus a value of 0.5 will trigger `onEndReached` when the end of the content is
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* within half the visible length of the list.
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*/
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onEndReachedThreshold?: ?number,
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/**
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* If provided, a standard RefreshControl will be added for "Pull to Refresh" functionality. Make
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* sure to also set the `refreshing` prop correctly.
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*/
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onRefresh?: ?() => void,
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/**
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* Called when the viewability of rows changes, as defined by the `viewabilityConfig` prop.
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*/
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onViewableItemsChanged?: ?(info: {
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viewableItems: Array<ViewToken>,
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changed: Array<ViewToken>,
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}) => void,
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legacyImplementation?: ?boolean,
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/**
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* Set this true while waiting for new data from a refresh.
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*/
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refreshing?: ?boolean,
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/**
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* Note: may have bugs (missing content) in some circumstances - use at your own risk.
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*
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* This may improve scroll performance for large lists.
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*/
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removeClippedSubviews?: boolean,
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/**
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* See `ViewabilityHelper` for flow type and further documentation.
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*/
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viewabilityConfig?: ViewabilityConfig,
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};
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type Props<ItemT> = RequiredProps<ItemT> & OptionalProps<ItemT> & VirtualizedListProps;
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const defaultProps = {
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...VirtualizedList.defaultProps,
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numColumns: 1,
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};
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type DefaultProps = typeof defaultProps;
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/**
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* A performant interface for rendering simple, flat lists, supporting the most handy features:
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*
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* - Fully cross-platform.
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* - Optional horizontal mode.
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* - Configurable viewability callbacks.
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* - Header support.
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* - Footer support.
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* - Separator support.
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* - Pull to Refresh.
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* - Scroll loading.
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* - ScrollToIndex support.
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*
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* If you need section support, use [`<SectionList>`](docs/sectionlist.html).
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*
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* Minimal Example:
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*
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* <FlatList
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* data={[{key: 'a'}, {key: 'b'}]}
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* renderItem={({item}) => <Text>{item.key}</Text>}
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* />
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*
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* More complex example demonstrating `PureComponent` usage for perf optimization and avoiding bugs.
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*
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* - By binding the `onPressItem` handler, the props will remain `===` and `PureComponent` will
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* prevent wasteful re-renders unless the actual `id`, `selected`, or `title` props change, even
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* if the inner `SomeOtherWidget` has no such optimizations.
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* - By passing `extraData={this.state}` to `FlatList` we make sure `FlatList` itself will re-render
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* when the `state.selected` changes. Without setting this prop, `FlatList` would not know it
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* needs to re-render any items because it is also a `PureComponent` and the prop comparison will
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* not show any changes.
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* - `keyExtractor` tells the list to use the `id`s for the react keys.
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*
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*
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* class MyListItem extends React.PureComponent {
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* _onPress = () => {
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* this.props.onPressItem(this.props.id);
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* };
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*
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* render() {
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* return (
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* <SomeOtherWidget
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* {...this.props}
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* onPress={this._onPress}
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* />
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* )
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* }
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* }
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*
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* class MyList extends React.PureComponent {
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* state = {selected: (new Map(): Map<string, boolean>)};
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*
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* _keyExtractor = (item, index) => item.id;
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*
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* _onPressItem = (id: string) => {
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* // updater functions are preferred for transactional updates
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* this.setState((state) => {
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* // copy the map rather than modifying state.
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* const selected = new Map(state.selected);
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* selected.set(id, !state.get(id)); // toggle
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* return {selected};
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* });
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* };
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*
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* _renderItem = ({item}) => (
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* <MyListItem
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* id={item.id}
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* onPressItem={this._onPressItem}
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* selected={!!this.state.selected.get(item.id)}
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* title={item.title}
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* />
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* );
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*
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* render() {
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* return (
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* <FlatList
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* data={this.props.data}
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* extraData={this.state}
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* keyExtractor={this._keyExtractor}
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* renderItem={this._renderItem}
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* />
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* );
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* }
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* }
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*
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* This is a convenience wrapper around [`<VirtualizedList>`](docs/virtualizedlist.html),
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* and thus inherits it's props (as well as those of `ScrollView`) that aren't explicitly listed
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* here, along with the following caveats:
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*
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* - Internal state is not preserved when content scrolls out of the render window. Make sure all
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* your data is captured in the item data or external stores like Flux, Redux, or Relay.
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* - This is a `PureComponent` which means that it will not re-render if `props` remain shallow-
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* equal. Make sure that everything your `renderItem` function depends on is passed as a prop
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* (e.g. `extraData`) that is not `===` after updates, otherwise your UI may not update on
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* changes. This includes the `data` prop and parent component state.
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* - In order to constrain memory and enable smooth scrolling, content is rendered asynchronously
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* offscreen. This means it's possible to scroll faster than the fill rate ands momentarily see
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* blank content. This is a tradeoff that can be adjusted to suit the needs of each application,
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* and we are working on improving it behind the scenes.
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* - By default, the list looks for a `key` prop on each item and uses that for the React key.
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* Alternatively, you can provide a custom `keyExtractor` prop.
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*
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*/
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class FlatList<ItemT> extends React.PureComponent<DefaultProps, Props<ItemT>, void> {
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static defaultProps: DefaultProps = defaultProps;
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props: Props<ItemT>;
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/**
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* Scrolls to the end of the content. May be janky without `getItemLayout` prop.
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*/
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scrollToEnd(params?: ?{animated?: ?boolean}) {
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this._listRef.scrollToEnd(params);
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}
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/**
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* Scrolls to the item at a the specified index such that it is positioned in the viewable area
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* such that `viewPosition` 0 places it at the top, 1 at the bottom, and 0.5 centered in the
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* middle. `viewOffset` is a fixed number of pixels to offset the final target position.
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*
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* Note: cannot scroll to locations outside the render window without specifying the
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* `getItemLayout` prop.
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*/
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scrollToIndex(params: {
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animated?: ?boolean, index: number, viewOffset?: number, viewPosition?: number,
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}) {
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this._listRef.scrollToIndex(params);
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}
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/**
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* Requires linear scan through data - use `scrollToIndex` instead if possible.
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*
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* Note: cannot scroll to locations outside the render window without specifying the
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* `getItemLayout` prop.
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*/
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scrollToItem(params: {animated?: ?boolean, item: ItemT, viewPosition?: number}) {
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this._listRef.scrollToItem(params);
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}
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/**
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* Scroll to a specific content pixel offset, like a normal `ScrollView`.
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*/
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scrollToOffset(params: {animated?: ?boolean, offset: number}) {
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this._listRef.scrollToOffset(params);
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}
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/**
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* Tells the list an interaction has occured, which should trigger viewability calculations, e.g.
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* if `waitForInteractions` is true and the user has not scrolled. This is typically called by
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* taps on items or by navigation actions.
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*/
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recordInteraction() {
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this._listRef.recordInteraction();
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}
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/**
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* Provides a handle to the underlying scroll responder.
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*/
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getScrollResponder() {
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if (this._listRef) {
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return this._listRef.getScrollResponder();
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}
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}
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getScrollableNode() {
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if (this._listRef) {
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return this._listRef.getScrollableNode();
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}
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}
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componentWillMount() {
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this._checkProps(this.props);
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}
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componentWillReceiveProps(nextProps: Props<ItemT>) {
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invariant(
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nextProps.numColumns === this.props.numColumns,
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'Changing numColumns on the fly is not supported. Change the key prop on FlatList when ' +
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'changing the number of columns to force a fresh render of the component.'
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);
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this._checkProps(nextProps);
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}
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_hasWarnedLegacy = false;
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_listRef: VirtualizedList;
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_captureRef = (ref) => { this._listRef = ref; };
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_checkProps(props: Props<ItemT>) {
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const {
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getItem,
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getItemCount,
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horizontal,
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legacyImplementation,
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numColumns,
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columnWrapperStyle,
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} = props;
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invariant(!getItem && !getItemCount, 'FlatList does not support custom data formats.');
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if (numColumns > 1) {
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invariant(!horizontal, 'numColumns does not support horizontal.');
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} else {
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invariant(!columnWrapperStyle, 'columnWrapperStyle not supported for single column lists');
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}
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if (legacyImplementation) {
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invariant(numColumns === 1, 'Legacy list does not support multiple columns.');
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// Warning: may not have full feature parity and is meant more for debugging and performance
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// comparison.
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if (!this._hasWarnedLegacy) {
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console.warn(
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'FlatList: Using legacyImplementation - some features not supported and performance ' +
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'may suffer'
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);
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this._hasWarnedLegacy = true;
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}
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}
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}
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_getItem = (data: Array<ItemT>, index: number) => {
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const {numColumns} = this.props;
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if (numColumns > 1) {
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const ret = [];
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for (let kk = 0; kk < numColumns; kk++) {
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const item = data[index * numColumns + kk];
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item && ret.push(item);
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}
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return ret;
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} else {
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return data[index];
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}
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};
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_getItemCount = (data: ?Array<ItemT>): number => {
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return data ? Math.ceil(data.length / this.props.numColumns) : 0;
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};
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_keyExtractor = (items: ItemT | Array<ItemT>, index: number) => {
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const {keyExtractor, numColumns} = this.props;
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if (numColumns > 1) {
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invariant(
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Array.isArray(items),
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'FlatList: Encountered internal consistency error, expected each item to consist of an ' +
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'array with 1-%s columns; instead, received a single item.',
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numColumns,
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);
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return items.map((it, kk) => keyExtractor(it, index * numColumns + kk)).join(':');
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} else {
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return keyExtractor(items, index);
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}
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};
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_pushMultiColumnViewable(arr: Array<ViewToken>, v: ViewToken): void {
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const {numColumns, keyExtractor} = this.props;
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v.item.forEach((item, ii) => {
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invariant(v.index != null, 'Missing index!');
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const index = v.index * numColumns + ii;
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arr.push({...v, item, key: keyExtractor(item, index), index});
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});
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}
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_onViewableItemsChanged = (info) => {
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const {numColumns, onViewableItemsChanged} = this.props;
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if (!onViewableItemsChanged) {
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return;
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}
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if (numColumns > 1) {
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const changed = [];
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const viewableItems = [];
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info.viewableItems.forEach((v) => this._pushMultiColumnViewable(viewableItems, v));
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info.changed.forEach((v) => this._pushMultiColumnViewable(changed, v));
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onViewableItemsChanged({viewableItems, changed});
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} else {
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onViewableItemsChanged(info);
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}
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};
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_renderItem = (info: Object) => {
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const {renderItem, numColumns, columnWrapperStyle} = this.props;
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if (numColumns > 1) {
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const {item, index} = info;
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invariant(Array.isArray(item), 'Expected array of items with numColumns > 1');
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return (
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<View style={[{flexDirection: 'row'}, columnWrapperStyle]}>
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{item.map((it, kk) => {
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const element = renderItem({
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item: it,
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index: index * numColumns + kk,
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separators: info.separators,
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});
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return element && React.cloneElement(element, {key: kk});
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})}
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</View>
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);
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} else {
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return renderItem(info);
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}
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};
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render() {
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if (this.props.legacyImplementation) {
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return <MetroListView {...this.props} items={this.props.data} ref={this._captureRef} />;
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} else {
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return (
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<VirtualizedList
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{...this.props}
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renderItem={this._renderItem}
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getItem={this._getItem}
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getItemCount={this._getItemCount}
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keyExtractor={this._keyExtractor}
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ref={this._captureRef}
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onViewableItemsChanged={this.props.onViewableItemsChanged && this._onViewableItemsChanged}
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/>
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);
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}
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}
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}
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module.exports = FlatList;
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