Get size of a View in React Native

Question

As of React Native 0.4.2, View components have an onLayout prop. Pass in a function that takes an event object. The event's nativeEvent contains the view's layout.

<View onLayout={(event) => {
  var {x, y, width, height} = event.nativeEvent.layout;
}} />

The onLayout handler will also be invoked whenever the view is resized.

The main caveat is that the onLayout handler is first invoked one frame after your component has mounted, so you may want to hide your UI until you have computed your layout.

This is the only thing that worked for me:

import React, { Component } from 'react';
import {
  AppRegistry,
  StyleSheet,
  Text,
  View,
  Image
} from 'react-native';

export default class Comp extends Component {

  find_dimesions(layout){
    const {x, y, width, height} = layout;
    console.warn(x);
    console.warn(y);
    console.warn(width);
    console.warn(height);
  }
  render() {
    return (
      <View onLayout={(event) => { this.find_dimesions(event.nativeEvent.layout) }} style={styles.container}>
        <Text style={styles.welcome}>
          Welcome to React Native!
        </Text>
        <Text style={styles.instructions}>
          To get started, edit index.android.js
        </Text>
        <Text style={styles.instructions}>
          Double tap R on your keyboard to reload,{'\n'}
          Shake or press menu button for dev menu
        </Text>
      </View>
    );
  }
}

const styles = StyleSheet.create({
  container: {
    flex: 1,
    justifyContent: 'center',
    alignItems: 'center',
    backgroundColor: '#F5FCFF',
  },
  welcome: {
    fontSize: 20,
    textAlign: 'center',
    margin: 10,
  },
  instructions: {
    textAlign: 'center',
    color: '#333333',
    marginBottom: 5,
  },
});

AppRegistry.registerComponent('Comp', () => Comp);

Basically if you want to set size and make it change then set it to state on layout like this:

import React, { Component } from 'react';
import { AppRegistry, StyleSheet, View } from 'react-native';

const styles = StyleSheet.create({
  container: {
    flex: 1,
    backgroundColor: 'yellow',
  },
  View1: {
    flex: 2,
    margin: 10,
    backgroundColor: 'red',
    elevation: 1,
  },
  View2: {
    position: 'absolute',
    backgroundColor: 'orange',
    zIndex: 3,
    elevation: 3,
  },
  View3: {
    flex: 3,
    backgroundColor: 'green',
    elevation: 2,
  },
  Text: {
    fontSize: 25,
    margin: 20,
    color: 'white',
  },
});

class Example extends Component {

  constructor(props) {
    super(props);

    this.state = {
      view2LayoutProps: {
        left: 0,
        top: 0,
        width: 50,
        height: 50,
      }
    };
  }

  onLayout(event) {
    const {x, y, height, width} = event.nativeEvent.layout;
    const newHeight = this.state.view2LayoutProps.height + 1;
    const newLayout = {
        height: newHeight ,
        width: width,
        left: x,
        top: y,
      };

    this.setState({ view2LayoutProps: newLayout });
  }

  render() {
    return (
      <View style={styles.container}>
        <View style={styles.View1}>
          <Text>{this.state.view2LayoutProps.height}</Text>
        </View>
        <View onLayout={(event) => this.onLayout(event)} 
              style={[styles.View2, this.state.view2LayoutProps]} />
        <View style={styles.View3} />
      </View>
    );
  }

}


AppRegistry.registerComponent(Example);

You can create many more variation of how it should be modified, by using this in another component which has Another view as wrapper and create an onResponderRelease callback, which could pass the touch event location into the state, which could be then passed to child component as property, which could override onLayout updated state, by placing {[styles.View2, this.state.view2LayoutProps, this.props.touchEventTopLeft]} and so on.

Maybe you can use measure:

measureProgressBar() {
    this.refs.welcome.measure(this.logProgressBarLayout);
},

logProgressBarLayout(ox, oy, width, height, px, py) {
  console.log("ox: " + ox);
  console.log("oy: " + oy);
  console.log("width: " + width);
  console.log("height: " + height);
  console.log("px: " + px);
  console.log("py: " + py);
}

You can easily get the size of the View by onLayout props.

import React from 'react'
import { View } from 'react-native'

export default function index() {
  const onLayout=(event)=> {
    const {x, y, height, width} = event.nativeEvent.layout;
    
  }
  return (
    <View onLayout={onLayout}>
      <OtherComponent />
    </View>
  )
}

The onLayout handler will also be invoked whenever the view is resized.

The main caveat is that the onLayout handler is first invoked one frame after your component has mounted, so you may want to hide your UI until you have computed your layout.