Height and Width #

A component's height and width determine its size on the screen.

Fixed Dimensions #

The simplest way to set the dimensions of a component is by adding a fixed width and height to style. All dimensions in React Native are unitless, and represent density-independent pixels.

import React, { Component } from 'react'; import { AppRegistry, View } from 'react-native'; export default class FixedDimensionsBasics extends Component { render() { return ( <View> <View style={{width: 50, height: 50, backgroundColor: 'powderblue'}} /> <View style={{width: 100, height: 100, backgroundColor: 'skyblue'}} /> <View style={{width: 150, height: 150, backgroundColor: 'steelblue'}} /> </View> ); } } // skip this line if using Create React Native App AppRegistry.registerComponent('AwesomeProject', () => FixedDimensionsBasics);

Setting dimensions this way is common for components that should always render at exactly the same size, regardless of screen dimensions.

Flex Dimensions #

Use flex in a component's style to have the component expand and shrink dynamically based on available space. Normally you will use flex: 1, which tells a component to fill all available space, shared evenly amongst each other component with the same parent. The larger the flex given, the higher the ratio of space a component will take compared to its siblings.

A component can only expand to fill available space if its parent has dimensions greater than 0. If a parent does not have either a fixed width and height or flex, the parent will have dimensions of 0 and the flex children will not be visible.

import React, { Component } from 'react'; import { AppRegistry, View } from 'react-native'; export default class FlexDimensionsBasics extends Component { render() { return ( // Try removing the `flex: 1` on the parent View. // The parent will not have dimensions, so the children can't expand. // What if you add `height: 300` instead of `flex: 1`? <View style={{flex: 1}}> <View style={{flex: 1, backgroundColor: 'powderblue'}} /> <View style={{flex: 2, backgroundColor: 'skyblue'}} /> <View style={{flex: 3, backgroundColor: 'steelblue'}} /> </View> ); } } // skip this line if using Create React Native App AppRegistry.registerComponent('AwesomeProject', () => FlexDimensionsBasics);

After you can control a component's size, the next step is to learn how to lay it out on the screen.

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