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API Reference

BarCodeScanner


expo-barcode-scanner provides a React component that renders a viewfinder for the device's camera (either front or back) and will scan bar codes that show up in the frame.

Platform Compatibility

Android DeviceAndroid EmulatoriOS DeviceiOS SimulatorWeb
Status-success-iconStatus-success-iconStatus-success-iconStatus-success-iconStatus-failed-icon
Info-icon

Note: Only one active BarCodeScanner preview is supported currently. When using navigation, the best practice is to unmount any previously rendered BarCodeScanner component so the following screens can use <BarCodeScanner /> without issues.

Installation

Terminal
expo install expo-barcode-scanner

If you're installing this in a bare React Native app, you should also follow these additional installation instructions.

Configuration

In managed apps, scanning barcodes with the camera requires the Permission.CAMERA permission. See the usage example below.

Supported formats

Bar code formatiOSAndroid
aztecYesYes
codabarYesYes
code39YesYes
code93YesYes
code128YesYes
code39mod43YesNo
datamatrixYesYes
ean13YesYes
ean8YesYes
interleaved2of5Yesuse itf14
itf14Yes*Yes
maxicodeNoYes
pdf417YesYes
rss14NoYes
rssexpandedNoYes
upc_aNoYes
upc_eYesYes
upc_eanNoYes
qrYesYes
Info-icon

Notes:

  • When an ITF-14 barcode is recognized, it's type can sometimes be set to interleaved2of5.
  • Scanning for either PDF417 and/or Code39 formats can result in a noticeable increase in battery consumption on iOS. It is recommended to provide only the bar code formats you expect to scan to the barCodeTypes prop.

Usage

You must request permission to access the user's camera before attempting to get it. To do this, you will want to use the Permissions API. You can see this in practice in the following example.

Basic BarCodeScanner usage
import React, { useState, useEffect } from 'react';
import { Text, View, StyleSheet, Button } from 'react-native';
import { BarCodeScanner } from 'expo-barcode-scanner';

export default function App() {
  const [hasPermission, setHasPermission] = useState(null);
  const [scanned, setScanned] = useState(false);

  useEffect(() => {
    (async () => {
      const { status } = await BarCodeScanner.requestPermissionsAsync();
      setHasPermission(status === 'granted');
    })();
  }, []);

  const handleBarCodeScanned = ({ type, data }) => {
    setScanned(true);
    alert(`Bar code with type ${type} and data ${data} has been scanned!`);
  };

  if (hasPermission === null) {
    return <Text>Requesting for camera permission</Text>;
  }
  if (hasPermission === false) {
    return <Text>No access to camera</Text>;
  }

  return (
    <View style={styles.container}>
      <BarCodeScanner
        onBarCodeScanned={scanned ? undefined : handleBarCodeScanned}
        style={StyleSheet.absoluteFillObject}
      />
      {scanned && <Button title={'Tap to Scan Again'} onPress={() => setScanned(false)} />}
    </View>
  );
}

%%placeholder-start%%const styles = StyleSheet.create({ ... }); %%placeholder-end%%const styles = StyleSheet.create({
  container: {
    flex: 1,
    flexDirection: 'column',
    justifyContent: 'center',
  },
});

API

import { BarCodeScanner } from 'expo-barcode-scanner';

Component

BarCodeScanner

Type: React.Component<BarCodeScannerProps>

Props

barCodeTypes

Optional • Type: string[]

An array of bar code types. Usage: BarCodeScanner.Constants.BarCodeType.<codeType> where codeType is one of these listed above. Defaults to all supported bar code types. It is recommended to provide only the bar code formats you expect to scan to minimize battery usage.

For example: barCodeTypes={[BarCodeScanner.Constants.BarCodeType.qr]}.

onBarCodeScanned

Optional • Type: BarCodeScannedCallback

A callback that is invoked when a bar code has been successfully scanned. The callback is provided with an BarCodeScannerResult.

Info-icon

Note: Passing undefined to the onBarCodeScanned prop will result in no scanning. This can be used to effectively "pause" the scanner so that it doesn't continually scan even after data has been retrieved.

type

Optional • Type: 'front' | 'back' | number • Default: Type.back

Camera facing. Use one of BarCodeScanner.Constants.Type. Use either Type.front or Type.back. Same as Camera.Constants.Type.

Inherited Props

  • ViewProps

Hooks

usePermissions(options)

NameTypeDescription
options
(optional)
PermissionHookOptions<object>-

Create a new permission hook with the permission methods built-in. This can be used to quickly create specific permission hooks in every module.

  • Undo-icon[null | PermissionResponse, RequestPermissionMethod<PermissionResponse>, GetPermissionMethod<PermissionResponse>]

usePermissions(options)

NameTypeDescription
options
(optional)
PermissionHookOptions<object>-

Check or request permissions for the barcode scanner. This uses both requestPermissionAsync and getPermissionsAsync to interact with the permissions.

Example

const [status, requestPermission] = BarCodeScanner.usePermissions();

Methods

BarCodeScanner.getPermissionsAsync()

Checks user's permissions for accessing the camera.


Return a promise that fulfills to an object of type PermissionResponse.

BarCodeScanner.requestPermissionsAsync()

Asks the user to grant permissions for accessing the camera.

On iOS this will require apps to specify the NSCameraUsageDescription entry in the Info.plist.


Return a promise that fulfills to an object of type PermissionResponse.

BarCodeScanner.scanFromURLAsync(url, barCodeTypes)

NameTypeDescription
urlstring

URL to get the image from.

barCodeTypes
(optional)
string[]

An array of bar code types. Defaults to all supported bar code types on the platform.

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Note: Only QR codes are supported on iOS.


Scan bar codes from the image given by the URL.


A possibly empty array of objects of the BarCodeScannerResult shape, where the type refers to the bar code type that was scanned and the data is the information encoded in the bar code.

Interfaces

PermissionResponse

An object obtained by getPermissionsAsync and requestPermissionsAsync functions.

NameTypeDescription
canAskAgainboolean

Indicates if user can be asked again for specific permission. If not, one should be directed to the Settings app in order to enable/disable the permission.

expiresPermissionExpiration

Determines time when the permission expires.

grantedboolean

A convenience boolean that indicates if the permission is granted.

statusPermissionStatus

Determines the status of the permission.


Types

BarCodeBounds

NameTypeDescription
originBarCodePoint

The origin point of the bounding box.

sizeBarCodeSize

The size of the bounding box.

BarCodeEvent

BarCodeScannerResult extended by:


NameTypeDescription
target
(optional)
number-

BarCodeEventCallbackArguments

NameTypeDescription
nativeEventBarCodeEvent-

BarCodePoint

Those coordinates are represented in the coordinate space of the barcode source (e.g. when you are using the barcode scanner view, these values are adjusted to the dimensions of the view).

NameTypeDescription
xnumber

The x coordinate value.

ynumber

The y coordinate value.

BarCodeScannedCallback()

NameTypeDescription
paramsBarCodeEvent-

BarCodeScannerResult

Info-icon

Note: bounds and cornerPoints are not always available. On iOS, for code39 and pdf417 you don't get those values. Moreover, on iOS, those values don't have to bounds the whole barcode. For some types, they will represent the area used by the scanner.

NameTypeDescription
bounds
(optional)
BarCodeBounds

The BarCodeBounds object.

cornerPoints
(optional)
BarCodePoint[]

Corner points of the bounding box.

datastring

The information encoded in the bar code.

typestring

The barcode type.

BarCodeSize

NameTypeDescription
heightnumber

The height value.

widthnumber

The width value.

PermissionHookOptions

Acceptable values are: PermissionHookBehavior, Options.

Enums

PermissionStatus

DENIED

PermissionStatus.DENIED = "denied"

User has denied the permission.

GRANTED

PermissionStatus.GRANTED = "granted"

User has granted the permission.

UNDETERMINED

PermissionStatus.UNDETERMINED = "undetermined"

User hasn't granted or denied the permission yet.

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