/** * Copyright (c) Meta Platforms, Inc. and affiliates. * * This source code is licensed under the MIT license found in the * LICENSE file in the root directory of this source tree. * * @flow * @format */ 'use strict'; import type {RNTesterModuleExample} from '../../types/RNTesterTypes'; import type { ViewLayout, ViewLayoutEvent, } from 'react-native/Libraries/Components/View/ViewPropTypes'; import RNTesterText from '../../components/RNTesterText'; import React from 'react'; import {Image, LayoutAnimation, StyleSheet, View} from 'react-native'; type Props = $ReadOnly<{}>; type State = { containerStyle?: {width: number}, extraText?: string, imageLayout?: ViewLayout, textLayout?: ViewLayout, viewLayout?: ViewLayout, viewStyle: {margin: number}, ... }; class LayoutEventExample extends React.Component { state: State = { viewStyle: { margin: 20, }, }; animateViewLayout = () => { LayoutAnimation.configureNext(LayoutAnimation.Presets.spring, () => { console.log('layout animation done.'); this.addWrapText(); }); this.setState({ viewStyle: { margin: this.state.viewStyle.margin > 20 ? 20 : 60, }, }); }; addWrapText = () => { this.setState( {extraText: ' And a bunch more text to wrap around a few lines.'}, this.changeContainer, ); }; changeContainer = () => { this.setState({containerStyle: {width: 280}}); }; onViewLayout = (e: ViewLayoutEvent) => { console.log('received view layout event\n', e.nativeEvent); this.setState({viewLayout: e.nativeEvent.layout}); }; onTextLayout = (e: ViewLayoutEvent) => { console.log('received text layout event\n', e.nativeEvent); this.setState({textLayout: e.nativeEvent.layout}); }; onImageLayout = (e: ViewLayoutEvent) => { console.log('received image layout event\n', e.nativeEvent); this.setState({imageLayout: e.nativeEvent.layout}); }; render(): React.Node { const viewStyle = [styles.view, this.state.viewStyle]; const textLayout = this.state.textLayout || {width: '?', height: '?'}; const imageLayout = this.state.imageLayout || {x: '?', y: '?'}; return ( layout events are called on mount and whenever layout is recalculated. Note that the layout event will typically be received{' '} before the layout has updated on screen, especially when using layout animations. {' '} Press here to change layout. ViewLayout:{' '} { /* $FlowFixMe[incompatible-type] (>=0.95.0 site=react_native_fb) * This comment suppresses an error found when Flow v0.95 was * deployed. To see the error, delete this comment and run Flow. */ // $FlowFixMe[unsafe-addition] JSON.stringify(this.state.viewLayout, null, ' ') + '\n\n' } A simple piece of text.{this.state.extraText} {'\n'} Text w/h: {textLayout.width}/{textLayout.height + '\n'} Image x/y: {imageLayout.x}/{imageLayout.y} ); } } const styles = StyleSheet.create({ view: { padding: 12, borderColor: 'black', borderWidth: 0.5, backgroundColor: 'transparent', }, text: { alignSelf: 'flex-start', borderColor: 'rgba(0, 0, 255, 0.2)', borderWidth: 0.5, }, image: { width: 50, height: 50, marginBottom: 10, alignSelf: 'center', }, pressText: { fontWeight: 'bold', }, italicText: { fontStyle: 'italic', }, }); exports.title = 'Layout Events'; exports.category = 'UI'; exports.description = ('Examples that show how Layout events can be used to ' + 'measure view size and position.': string); exports.examples = [ { title: 'LayoutEventExample', render: function (): React.MixedElement { return ; }, }, ] as Array;