React Native0.41

The Basics

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Layout with Flexbox #

A component can specify the layout of its children using the flexbox algorithm. Flexbox is designed to provide a consistent layout on different screen sizes.

You will normally use a combination of flexDirection, alignItems, and justifyContent to achieve the right layout.

Flexbox works the same way in React Native as it does in CSS on the web, with a few exceptions. The defaults are different, with flexDirection defaulting to column instead of row, and the flex parameter only supporting a single number.

Flex Direction #

Adding flexDirection to a component's style determines the primary axis of its layout. Should the children be organized horizontally (row) or vertically (column)? The default is column.

import React, { Component } from 'react'; import { AppRegistry, View } from 'react-native'; class FlexDirectionBasics extends Component { render() { return ( // Try setting `flexDirection` to `column`. <View style={{flex: 1, flexDirection: 'row'}}> <View style={{width: 50, height: 50, backgroundColor: 'powderblue'}} /> <View style={{width: 50, height: 50, backgroundColor: 'skyblue'}} /> <View style={{width: 50, height: 50, backgroundColor: 'steelblue'}} /> </View> ); } }; AppRegistry.registerComponent('AwesomeProject', () => FlexDirectionBasics);

Justify Content #

Adding justifyContent to a component's style determines the distribution of children along the primary axis. Should children be distributed at the start, the center, the end, or spaced evenly? Available options are flex-start, center, flex-end, space-around, and space-between.

import React, { Component } from 'react'; import { AppRegistry, View } from 'react-native'; class JustifyContentBasics extends Component { render() { return ( // Try setting `justifyContent` to `center`. // Try setting `flexDirection` to `row`. <View style={{ flex: 1, flexDirection: 'column', justifyContent: 'space-between', }}> <View style={{width: 50, height: 50, backgroundColor: 'powderblue'}} /> <View style={{width: 50, height: 50, backgroundColor: 'skyblue'}} /> <View style={{width: 50, height: 50, backgroundColor: 'steelblue'}} /> </View> ); } }; AppRegistry.registerComponent('AwesomeProject', () => JustifyContentBasics);

Align Items #

Adding alignItems to a component's style determines the alignment of children along the secondary axis (if the primary axis is row, then the secondary is column, and vice versa). Should children be aligned at the start, the center, the end, or stretched to fill? Available options are flex-start, center, flex-end, and stretch.

For stretch to have an effect, children must not have a fixed dimension along the secondary axis. In the following example, setting alignItems: stretch does nothing until the width: 50 is removed from the children.

import React, { Component } from 'react'; import { AppRegistry, View } from 'react-native'; class AlignItemsBasics extends Component { render() { return ( // Try setting `alignItems` to 'flex-start' // Try setting `justifyContent` to `flex-end`. // Try setting `flexDirection` to `row`. <View style={{ flex: 1, flexDirection: 'column', justifyContent: 'center', alignItems: 'center', }}> <View style={{width: 50, height: 50, backgroundColor: 'powderblue'}} /> <View style={{width: 50, height: 50, backgroundColor: 'skyblue'}} /> <View style={{width: 50, height: 50, backgroundColor: 'steelblue'}} /> </View> ); } }; AppRegistry.registerComponent('AwesomeProject', () => AlignItemsBasics);

Going Deeper #

We've covered the basics, but there are many other styles you may need for layouts. The full list of props that control layout is documented here.

We're getting close to being able to build a real application. One thing we are still missing is a way to take user input, so let's move on to learn how to handle text input with the TextInput component.

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