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VirtualizedList.js
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VirtualizedList.js
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/**
* Copyright (c) 2013-present, Facebook, Inc.
* All rights reserved.
*
* This source code is licensed under the BSD-style license found in the
* LICENSE file in the root directory of this source tree. An additional grant
* of patent rights can be found in the PATENTS file in the same directory.
*
* Facebook, Inc. ("Facebook") owns all right, title and interest, including
* all intellectual property and other proprietary rights, in and to the React
* Native CustomComponents software (the "Software"). Subject to your
* compliance with these terms, you are hereby granted a non-exclusive,
* worldwide, royalty-free copyright license to (1) use and copy the Software;
* and (2) reproduce and distribute the Software as part of your own software
* ("Your Software"). Facebook reserves all rights not expressly granted to
* you in this license agreement.
*
* THE SOFTWARE AND DOCUMENTATION, IF ANY, ARE PROVIDED "AS IS" AND ANY EXPRESS
* OR IMPLIED WARRANTIES (INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE) ARE DISCLAIMED.
* IN NO EVENT SHALL FACEBOOK OR ITS AFFILIATES, OFFICERS, DIRECTORS OR
* EMPLOYEES BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
* OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
* WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
* OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THE SOFTWARE, EVEN IF
* ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*
* @providesModule VirtualizedList
* @flow
*/
'use strict';
const Batchinator = require('Batchinator');
const React = require('React');
const RefreshControl = require('RefreshControl');
const ScrollView = require('ScrollView');
const View = require('View');
const ViewabilityHelper = require('ViewabilityHelper');
const infoLog = require('infoLog');
const invariant = require('fbjs/lib/invariant');
const {computeWindowedRenderLimits} = require('VirtualizeUtils');
import type {Viewable} from 'ViewabilityHelper';
type Item = any;
type ItemComponentType = ReactClass<{item: Item, index: number}>;
/**
* Renders a virtual list of items given a data blob and accessor functions. Items that are outside
* the render window (except for the initial items at the top) are 'virtualized' e.g. unmounted or
* never rendered in the first place. This improves performance and saves memory for large data
* sets, but will reset state on items that scroll too far out of the render window.
*
* TODO: Note that LayoutAnimation and sticky section headers both have bugs when used with this and
* are therefor not supported, but new Animated impl might work?
* https://github.com/facebook/react-native/pull/11315
*
* TODO: removeClippedSubviews might not be necessary and may cause bugs?
*
*/
type RequiredProps = {
ItemComponent: ItemComponentType,
/**
* The default accessor functions assume this is an Array<{key: string}> but you can override
* getItem, getItemCount, and keyExtractor to handle any type of index-based data.
*/
data: any,
};
type OptionalProps = {
FooterComponent?: ?ReactClass<*>,
HeaderComponent?: ?ReactClass<*>,
SeparatorComponent?: ?ReactClass<*>,
/**
* `debug` will turn on extra logging and visual overlays to aid with debugging both usage and
* implementation.
*/
debug?: ?boolean,
/**
* DEPRECATED: Virtualization provides significant performance and memory optimizations, but fully
* unmounts react instances that are outside of the render window. You should only need to disable
* this for debugging purposes.
*/
disableVirtualization: boolean,
getItem: (items: any, index: number) => ?Item,
getItemCount: (items: any) => number,
getItemLayout?: (items: any, index: number) =>
{length: number, offset: number, index: number}, // e.g. height, y
horizontal: boolean,
initialNumToRender: number,
keyExtractor: (item: Item, index: number) => string,
maxToRenderPerBatch: number,
onEndReached: ({distanceFromEnd: number}) => void,
onEndReachedThreshold: number, // units of visible length
onLayout?: ?Function,
/**
* If provided, a standard RefreshControl will be added for "Pull to Refresh" functionality. Make
* sure to also set the `refreshing` prop correctly.
*/
onRefresh?: ?Function,
/**
* Called when the viewability of rows changes, as defined by the
* `viewablePercentThreshold` prop.
*/
onViewableItemsChanged?: ({viewableItems: Array<Viewable>, changed: Array<Viewable>}) => void,
/**
* Set this true while waiting for new data from a refresh.
*/
refreshing?: boolean,
removeClippedSubviews?: boolean,
renderScrollComponent: (props: Object) => React.Element<*>,
shouldItemUpdate: (
props: {item: Item, index: number},
nextProps: {item: Item, index: number}
) => boolean,
updateCellsBatchingPeriod: number,
/**
* 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.
*/
viewablePercentThreshold: number,
windowSize: number, // units of visible length
};
type Props = RequiredProps & OptionalProps;
let _usedIndexForKey = false;
class VirtualizedList extends React.PureComponent {
props: Props;
// scrollToEnd may be janky without getItemLayout prop
scrollToEnd(params?: ?{animated?: ?boolean}) {
const animated = params ? params.animated : true;
const veryLast = this.props.getItemCount(this.props.data) - 1;
const frame = this._getFrameMetricsApprox(veryLast);
const offset = frame.offset + frame.length + this._footerLength -
this._scrollMetrics.visibleLength;
this._scrollRef.scrollTo(
this.props.horizontal ? {x: offset, animated} : {y: offset, animated}
);
}
// scrollToIndex may be janky without getItemLayout prop
scrollToIndex(params: {animated?: ?boolean, index: number, viewPosition?: number}) {
const {data, horizontal, getItemCount} = this.props;
const {animated, index, viewPosition} = params;
if (!(index >= 0 && index < getItemCount(data))) {
console.warn('scrollToIndex out of range ' + index);
return;
}
const frame = this._getFrameMetricsApprox(index);
const offset = Math.max(
0,
frame.offset - (viewPosition || 0) * (this._scrollMetrics.visibleLength - frame.length),
);
this._scrollRef.scrollTo(horizontal ? {x: offset, animated} : {y: offset, animated});
}
// scrollToItem may be janky without getItemLayout prop. Required linear scan through items -
// use scrollToIndex instead if possible.
scrollToItem(params: {animated?: ?boolean, item: Item, viewPosition?: number}) {
const {item} = params;
const {data, getItem, getItemCount} = this.props;
const itemCount = getItemCount(data);
for (let index = 0; index < itemCount; index++) {
if (getItem(data, index) === item) {
this.scrollToIndex({...params, index});
break;
}
}
}
scrollToOffset(params: {animated?: ?boolean, offset: number}) {
const {animated, offset} = params;
this._scrollRef.scrollTo(
this.props.horizontal ? {x: offset, animated} : {y: offset, animated}
);
}
static defaultProps: OptionalProps = {
disableVirtualization: false,
getItem: (data: any, index: number) => data[index],
getItemCount: (data: any) => data ? data.length : 0,
horizontal: false,
initialNumToRender: 10,
keyExtractor: (item: Item, index: number) => {
if (item.key != null) {
return item.key;
}
_usedIndexForKey = true;
return String(index);
},
maxToRenderPerBatch: 10,
onEndReached: () => {},
onEndReachedThreshold: 2, // multiples of length
removeClippedSubviews: true,
renderScrollComponent: (props: Props) => {
if (props.onRefresh) {
invariant(
typeof props.refreshing === 'boolean',
'`refreshing` prop must be set as a boolean in order to use `onRefresh`, but got `' +
JSON.stringify(props.refreshing) + '`',
);
return (
<ScrollView
{...props}
refreshControl={
<RefreshControl
refreshing={props.refreshing}
onRefresh={props.onRefresh}
/>
}
/>
);
} else {
return <ScrollView {...props} />;
}
},
shouldItemUpdate: (
props: {item: Item, index: number},
nextProps: {item: Item, index: number},
) => true,
updateCellsBatchingPeriod: 50,
viewablePercentThreshold: 10,
windowSize: 21, // multiples of length
};
state = {
first: 0,
last: this.props.initialNumToRender,
};
constructor(props: Props) {
super(props);
this._updateCellsToRenderBatcher = new Batchinator(
this._updateCellsToRender,
this.props.updateCellsBatchingPeriod,
);
this.state = {
first: 0,
last: Math.min(this.props.getItemCount(this.props.data), this.props.initialNumToRender) - 1,
};
}
componentWillUnmount() {
this._updateViewableItems(null);
this._updateCellsToRenderBatcher.dispose();
}
componentWillReceiveProps(newProps: Props) {
const {data, getItemCount, maxToRenderPerBatch} = newProps;
// first and last could be stale (e.g. if a new, shorter items props is passed in), so we make
// sure we're rendering a reasonable range here.
this.setState({
first: Math.max(0, Math.min(this.state.first, getItemCount(data) - 1 - maxToRenderPerBatch)),
last: Math.max(0, Math.min(this.state.last, getItemCount(data) - 1)),
});
this._updateCellsToRenderBatcher.schedule();
}
_pushCells(cells, first, last) {
const {SeparatorComponent, data, getItem, getItemCount, keyExtractor} = this.props;
const end = getItemCount(data) - 1;
last = Math.min(end, last);
for (let ii = first; ii <= last; ii++) {
const item = getItem(data, ii);
invariant(item, 'No item for index ' + ii);
const key = keyExtractor(item, ii);
cells.push(
<CellRenderer
cellKey={key}
index={ii}
item={item}
key={key}
onLayout={this._onCellLayout}
onUnmount={this._onCellUnmount}
parentProps={this.props}
/>
);
if (SeparatorComponent && ii < end) {
cells.push(<SeparatorComponent key={'sep' + ii}/>);
}
}
}
render() {
const {FooterComponent, HeaderComponent} = this.props;
const {data, disableVirtualization, horizontal} = this.props;
const cells = [];
if (HeaderComponent) {
cells.push(
<View key="$header" onLayout={this._onLayoutHeader}>
<HeaderComponent />
</View>
);
}
const itemCount = this.props.getItemCount(data);
if (itemCount > 0) {
_usedIndexForKey = false;
const lastInitialIndex = this.props.initialNumToRender - 1;
const {first, last} = this.state;
this._pushCells(cells, 0, lastInitialIndex);
if (!disableVirtualization && first > lastInitialIndex) {
const initBlock = this._getFrameMetricsApprox(lastInitialIndex);
const firstSpace = this._getFrameMetricsApprox(first).offset -
(initBlock.offset + initBlock.length);
cells.push(
<View key="$lead_spacer" style={{[!horizontal ? 'height' : 'width']: firstSpace}} />
);
}
this._pushCells(cells, Math.max(lastInitialIndex + 1, first), last);
if (!this._hasWarned.keys && _usedIndexForKey) {
console.warn(
'VirtualizedList: missing keys for items, make sure to specify a key property on each ' +
'item or provide a custom keyExtractor.'
);
this._hasWarned.keys = true;
}
if (!disableVirtualization && last < itemCount - 1) {
const lastFrame = this._getFrameMetricsApprox(last);
const end = this.props.getItemLayout ?
itemCount - 1 :
Math.min(itemCount - 1, this._highestMeasuredFrameIndex);
const endFrame = this._getFrameMetricsApprox(end);
const tailSpacerLength =
(endFrame.offset + endFrame.length) -
(lastFrame.offset + lastFrame.length);
cells.push(
<View key="$tail_spacer" style={{[!horizontal ? 'height' : 'width']: tailSpacerLength}} />
);
}
}
if (FooterComponent) {
cells.push(
<View key="$footer" onLayout={this._onLayoutFooter}>
<FooterComponent />
</View>
);
}
const ret = React.cloneElement(
this.props.renderScrollComponent(this.props),
{
onContentSizeChange: this._onContentSizeChange,
onLayout: this._onLayout,
onScroll: this._onScroll,
ref: this._captureScrollRef,
scrollEventThrottle: 50, // TODO: Android support
},
cells,
);
if (this.props.debug) {
return <View style={{flex: 1}}>{ret}{this._renderDebugOverlay()}</View>;
} else {
return ret;
}
}
componentDidUpdate() {
this._updateCellsToRenderBatcher.schedule();
}
_averageCellLength = 0;
_hasWarned = {};
_highestMeasuredFrameIndex = 0;
_headerLength = 0;
_frames = {};
_footerLength = 0;
_scrollMetrics = {
visibleLength: 0, contentLength: 0, offset: 0, dt: 10, velocity: 0, timestamp: 0,
};
_scrollRef = (null: any);
_sentEndForContentLength = 0;
_totalCellLength = 0;
_totalCellsMeasured = 0;
_updateCellsToRenderBatcher: Batchinator;
_viewableKeys: {[key: string]: boolean} = {};
_viewableItems: Array<Viewable> = [];
_captureScrollRef = (ref) => {
this._scrollRef = ref;
};
_onCellLayout = (e, cellKey, index) => {
const layout = e.nativeEvent.layout;
const next = {offset: this._selectOffset(layout), length: this._selectLength(layout), index, inLayout: true};
const curr = this._frames[cellKey];
if (!curr ||
next.offset !== curr.offset ||
next.length !== curr.length ||
index !== curr.index
) {
this._totalCellLength += next.length - (curr ? curr.length : 0);
this._totalCellsMeasured += (curr ? 0 : 1);
this._averageCellLength = this._totalCellLength / this._totalCellsMeasured;
this._frames[cellKey] = next;
this._highestMeasuredFrameIndex = Math.max(this._highestMeasuredFrameIndex, index);
this._updateCellsToRenderBatcher.schedule();
}
};
_onCellUnmount = (cellKey: string) => {
const curr = this._frames[cellKey];
if (curr) {
this._frames[cellKey] = {...curr, inLayout: false};
}
};
_onLayout = (e: Object) => {
this._scrollMetrics.visibleLength = this._selectLength(e.nativeEvent.layout);
this.props.onLayout && this.props.onLayout(e);
this._updateCellsToRenderBatcher.schedule();
};
_onLayoutFooter = (e) => {
this._footerLength = this._selectLength(e.nativeEvent.layout);
};
_onLayoutHeader = (e) => {
this._headerLength = this._selectLength(e.nativeEvent.layout);
};
_renderDebugOverlay() {
const normalize = this._scrollMetrics.visibleLength / this._scrollMetrics.contentLength;
const framesInLayout = [];
const itemCount = this.props.getItemCount(this.props.data);
for (let ii = 0; ii < itemCount; ii++) {
const frame = this._getFrameMetricsApprox(ii);
if (frame.inLayout) {
framesInLayout.push(frame);
}
}
const windowTop = this._getFrameMetricsApprox(this.state.first).offset;
const frameLast = this._getFrameMetricsApprox(this.state.last);
const windowLen = frameLast.offset + frameLast.length - windowTop;
const visTop = this._scrollMetrics.offset;
const visLen = this._scrollMetrics.visibleLength;
const baseStyle = {position: 'absolute', top: 0, right: 0};
return (
<View style={{...baseStyle, bottom: 0, width: 20, borderColor: 'blue', borderWidth: 1}}>
{framesInLayout.map((f, ii) =>
<View key={'f' + ii} style={{
...baseStyle,
left: 0,
top: f.offset * normalize,
height: f.length * normalize,
backgroundColor: 'orange',
}} />
)}
<View style={{
...baseStyle,
left: 0,
top: windowTop * normalize,
height: windowLen * normalize,
borderColor: 'green',
borderWidth: 2,
}} />
<View style={{
...baseStyle,
left: 0,
top: visTop * normalize,
height: visLen * normalize,
borderColor: 'red',
borderWidth: 2,
}} />
</View>
);
}
_selectLength(metrics: {height: number, width: number}): number {
return !this.props.horizontal ? metrics.height : metrics.width;
}
_selectOffset(metrics: {x: number, y: number}): number {
return !this.props.horizontal ? metrics.y : metrics.x;
}
_onContentSizeChange = (width: number, height: number) => {
this._scrollMetrics.contentLength = this._selectLength({height, width});
this._updateCellsToRenderBatcher.schedule();
};
_onScroll = (e: Object) => {
const timestamp = e.timeStamp;
const visibleLength = this._selectLength(e.nativeEvent.layoutMeasurement);
const contentLength = this._selectLength(e.nativeEvent.contentSize);
const offset = this._selectOffset(e.nativeEvent.contentOffset);
const dt = Math.max(1, timestamp - this._scrollMetrics.timestamp);
if (dt > 500 && this._scrollMetrics.dt > 500 && (contentLength > (5 * visibleLength)) &&
!this._hasWarned.perf) {
infoLog(
'VirtualizedList: You have a large list that is slow to update - make sure ' +
'shouldItemUpdate is implemented effectively and consider getItemLayout, PureComponent, ' +
'etc.',
{dt, prevDt: this._scrollMetrics.dt, contentLength},
);
this._hasWarned.perf = true;
}
const dOffset = offset - this._scrollMetrics.offset;
const velocity = dOffset / dt;
this._scrollMetrics = {contentLength, dt, offset, timestamp, velocity, visibleLength};
const {data, getItemCount, onEndReached, onEndReachedThreshold, windowSize} = this.props;
if (!data) {
return;
}
const distanceFromEnd = contentLength - visibleLength - offset;
const itemCount = getItemCount(data);
if (distanceFromEnd < onEndReachedThreshold * visibleLength &&
this._scrollMetrics.contentLength !== this._sentEndForContentLength &&
this.state.last === itemCount - 1) {
// Only call onEndReached for a given content length once.
this._sentEndForContentLength = this._scrollMetrics.contentLength;
onEndReached({distanceFromEnd});
}
const {first, last} = this.state;
if ((first > 0 && velocity < 0) || (last < itemCount - 1 && velocity > 0)) {
const distanceToContentEdge = Math.min(
Math.abs(this._getFrameMetricsApprox(first).offset - offset),
Math.abs(this._getFrameMetricsApprox(last).offset - (offset + visibleLength)),
);
const hiPri = distanceToContentEdge < (windowSize * visibleLength / 4);
if (hiPri) {
// Don't worry about interactions when scrolling quickly; focus on filling content as fast
// as possible.
this._updateCellsToRenderBatcher.dispose({abort: true});
this._updateCellsToRender();
return;
}
}
this._updateCellsToRenderBatcher.schedule();
};
_updateCellsToRender = () => {
const {data, disableVirtualization, getItemCount, onEndReachedThreshold} = this.props;
this._updateViewableItems(data);
if (!data) {
return;
}
this.setState((state) => {
let newState;
if (!disableVirtualization) {
newState = computeWindowedRenderLimits(
this.props, state, this._getFrameMetricsApprox, this._scrollMetrics,
);
} else {
const {contentLength, offset, visibleLength} = this._scrollMetrics;
const distanceFromEnd = contentLength - visibleLength - offset;
const renderAhead = distanceFromEnd < onEndReachedThreshold * visibleLength ?
this.props.maxToRenderPerBatch : 0;
newState = {
first: 0,
last: Math.min(state.last + renderAhead, getItemCount(data) - 1),
};
}
return newState;
});
};
_createViewable(index: number, isViewable: boolean): Viewable {
const {data, getItem, keyExtractor} = this.props;
const item = getItem(data, index);
invariant(item, 'Missing item for index ' + index);
return {index, item, key: keyExtractor(item, index), isViewable};
}
_getFrameMetricsApprox = (index: number): {length: number, offset: number} => {
const frame = this._getFrameMetrics(index);
if (frame && frame.index === index) { // check for invalid frames due to row re-ordering
return frame;
} else {
const {getItemLayout} = this.props;
invariant(
!getItemLayout,
'Should not have to estimate frames when a measurement metrics function is provided'
);
return {
length: this._averageCellLength,
offset: this._averageCellLength * index,
};
}
};
_getFrameMetrics = (index: number): ?{length: number, offset: number, index: number} => {
const {data, getItem, getItemCount, getItemLayout, keyExtractor} = this.props;
invariant(getItemCount(data) > index, 'Tried to get frame for out of range index ' + index);
const item = getItem(data, index);
let frame = item && this._frames[keyExtractor(item, index)];
if (!frame || frame.index !== index) {
if (getItemLayout) {
frame = getItemLayout(data, index);
}
}
return frame;
};
_updateViewableItems(data: any) {
const {getItemCount, onViewableItemsChanged, viewablePercentThreshold} = this.props;
if (!onViewableItemsChanged) {
return;
}
let viewableIndices = [];
if (data) {
viewableIndices = ViewabilityHelper.computeViewableItems(
viewablePercentThreshold,
getItemCount(data),
this._scrollMetrics.offset,
this._scrollMetrics.visibleLength,
this._getFrameMetrics,
this.state,
);
}
const viewableKeys = {};
const viewableItems = viewableIndices.map((ii) => {
const viewable = this._createViewable(ii, true);
viewableKeys[viewable.key] = true;
return viewable;
});
const changed = viewableItems.filter(v => !this._viewableKeys[v.key])
.concat(
this._viewableItems.filter(v => !viewableKeys[v.key])
.map(v => ({...v, isViewable: false}))
);
if (changed.length > 0) {
onViewableItemsChanged({viewableItems, changed});
this._viewableItems = viewableItems;
this._viewableKeys = viewableKeys;
}
}
}
class CellRenderer extends React.Component {
props: {
cellKey: string,
index: number,
item: Item,
onLayout: (event: Object, cellKey: string, index: number) => void,
onUnmount: (cellKey: string) => void,
parentProps: {
ItemComponent: ItemComponentType,
getItemLayout?: ?Function,
shouldItemUpdate: (
props: {item: Item, index: number},
nextProps: {item: Item, index: number}
) => boolean,
},
};
_onLayout = (e) => {
this.props.onLayout(e, this.props.cellKey, this.props.index);
}
componentWillUnmount() {
this.props.onUnmount(this.props.cellKey);
}
shouldComponentUpdate(nextProps, nextState) {
const curr = {item: this.props.item, index: this.props.index};
const next = {item: nextProps.item, index: nextProps.index};
return nextProps.parentProps.shouldItemUpdate(curr, next);
}
render() {
const {item, index, parentProps} = this.props;
const {ItemComponent, getItemLayout} = parentProps;
const element = <ItemComponent item={item} index={index} />;
if (getItemLayout && !parentProps.debug) {
return element;
}
return (
<View onLayout={this._onLayout}>
{element}
</View>
);
}
}
module.exports = VirtualizedList;