Created
May 11, 2017 04:24
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React Native component for measuring text height
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| // @flow | |
| import type { | |
| StyleObj, | |
| } from 'react-native/Libraries/StyleSheet/StyleSheetTypes'; | |
| import React from 'react'; | |
| import PropTypes from 'prop-types'; | |
| import { Text, View, StyleSheet } from 'react-native'; | |
| import invariant from 'invariant'; | |
| import _isEmpty from 'lodash/fp/isEmpty'; | |
| import _map from 'lodash/fp/map'; | |
| import _toArray from 'lodash/fp/toArray'; | |
| const measureBatchSize = 10; | |
| type TextToHeight = { [text: string]: number }; | |
| type Props = { | |
| textToMeasure: string[], | |
| allHeightsMeasuredCallback: ( | |
| textToMeasure: string[], | |
| heights: TextToHeight, | |
| ) => void, | |
| style: StyleObj, | |
| }; | |
| type State = { | |
| currentlyMeasuring: ?Set<string>, | |
| }; | |
| class TextHeightMeasurer extends React.PureComponent { | |
| props: Props; | |
| state: State = { | |
| currentlyMeasuring: null, | |
| }; | |
| static propTypes = { | |
| textToMeasure: PropTypes.arrayOf(PropTypes.string).isRequired, | |
| allHeightsMeasuredCallback: PropTypes.func.isRequired, | |
| style: Text.propTypes.style, | |
| }; | |
| currentTextToHeight: TextToHeight = {}; | |
| nextTextToHeight: ?TextToHeight = null; | |
| leftToMeasure: Set<string> = new Set(); | |
| leftInBatch = 0; | |
| constructor(props: Props) { | |
| super(props); | |
| this.resetInternalState(this.props.textToMeasure); | |
| } | |
| componentDidMount() { | |
| this.newBatch(); | |
| } | |
| componentWillReceiveProps(nextProps: Props) { | |
| if (nextProps.textToMeasure === this.props.textToMeasure) { | |
| return; | |
| } | |
| this.resetInternalState(nextProps.textToMeasure); | |
| this.newBatch(); | |
| } | |
| // resets this.leftToMeasure and this.nextTextToHeight | |
| resetInternalState(newTextToMeasure: string[]) { | |
| this.leftToMeasure = new Set(); | |
| const nextNextTextToHeight = {}; | |
| for (let text of newTextToMeasure) { | |
| if (this.currentTextToHeight[text]) { | |
| nextNextTextToHeight[text] = this.currentTextToHeight[text]; | |
| } else if (this.nextTextToHeight && this.nextTextToHeight[text]) { | |
| nextNextTextToHeight[text] = this.nextTextToHeight[text]; | |
| } else { | |
| this.leftToMeasure.add(text); | |
| } | |
| } | |
| this.nextTextToHeight = nextNextTextToHeight; | |
| } | |
| onTextLayout( | |
| text: string, | |
| event: { nativeEvent: { layout: { height: number }}}, | |
| ) { | |
| invariant(this.nextTextToHeight, "nextTextToHeight should be set"); | |
| this.nextTextToHeight[text] = event.nativeEvent.layout.height; | |
| this.leftToMeasure.delete(text); | |
| this.leftInBatch--; | |
| if (this.leftToMeasure.size === 0) { | |
| // We're done!! | |
| invariant(this.leftInBatch === 0, "batch should be complete"); | |
| invariant(this.nextTextToHeight, "nextTextToHeight should be set"); | |
| this.currentTextToHeight = this.nextTextToHeight; | |
| this.nextTextToHeight = null; | |
| this.props.allHeightsMeasuredCallback( | |
| this.props.textToMeasure, | |
| this.currentTextToHeight, | |
| ); | |
| this.setState({ currentlyMeasuring: null }); | |
| } else if (this.leftInBatch === 0) { | |
| this.newBatch(); | |
| } | |
| } | |
| newBatch() { | |
| let newBatchSize = Math.min(measureBatchSize, this.leftToMeasure.size); | |
| this.leftInBatch = newBatchSize; | |
| const newCurrentlyMeasuring = new Set(); | |
| const leftToMeasureIter = this.leftToMeasure.values(); | |
| for (; newBatchSize > 0; newBatchSize--) { | |
| const value = leftToMeasureIter.next().value; | |
| invariant(value, "item should exist"); | |
| newCurrentlyMeasuring.add(value); | |
| } | |
| this.setState({ currentlyMeasuring: newCurrentlyMeasuring }); | |
| } | |
| render() { | |
| if (_isEmpty(this.state.currentlyMeasuring)) { | |
| return null; | |
| } | |
| const set = this.state.currentlyMeasuring; | |
| invariant(set, "should be set"); | |
| const dummies = _map((text: string) => ( | |
| <Text | |
| style={[styles.text, this.props.style]} | |
| onLayout={(event) => this.onTextLayout(text, event)} | |
| key={text} | |
| > | |
| {text} | |
| </Text> | |
| ))(_toArray(this.state.currentlyMeasuring)); | |
| return <View>{dummies}</View>; | |
| } | |
| } | |
| const styles = StyleSheet.create({ | |
| text: { | |
| opacity: 0, | |
| position: 'absolute', | |
| }, | |
| }); | |
| export default TextHeightMeasurer; |
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