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.