Height and Width

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

Fixed Dimensions

The general 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 from 'react'; import { View } from 'react-native'; const FixedDimensionsBasics = () => { 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> ); }; export default 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 other components 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 from 'react'; import { View } from 'react-native'; const FlexDimensionsBasics = () => { 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> ); }; export default FlexDimensionsBasics;

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

Percentage Dimensions

If you want to fill a certain portion of the screen, but you don't want to use the flex layout, you can use percentage values in the component's style. Similar to flex dimensions, percentage dimensions require parent with a defined size.

import React from 'react'; import { View } from 'react-native'; const PercentageDimensionsBasics = () => { // Try removing the `height: '100%'` on the parent View. // The parent will not have dimensions, so the children can't expand. return ( <View style={{ height: '100%' }}> <View style={{ height: '15%', backgroundColor: 'powderblue' }} /> <View style={{ width: '66%', height: '35%', backgroundColor: 'skyblue' }} /> <View style={{ width: '33%', height: '50%', backgroundColor: 'steelblue' }} /> </View> ); }; export default PercentageDimensionsBasics;