QR/Barcode Scanning

What is a Code Scanner?

A Code Scanner is a separate Camera output (just like photo or video) that can detect a variety of machine-readable codes, such as:

• QR: Square QR codes
• Aztec: Square Aztec codes
• Data Matrix: Square Data Matrix codes
• Barcode (EAN): EAN-13 or EAN-8 Barcodes
• Barcode (Code): Code-128, Code-39 or Code-93 Barcodes
• Barcode (other): Codabar, ITF-14, UPC-E or PDF-417 Barcodes

Setup

On iOS, the Code Scanner uses the platform-native APIs and can be used out of the box.

On Android, the MLKit Vision Barcode Scanning API will be used, and the model (2.2MB) needs to be included into your app first.

React Native

Inside your gradle.properties file, add the enableCodeScanner flag:

VisionCamera_enableCodeScanner=true

Expo

Add the enableCodeScanner flag to your Expo config (app.json, app.config.json or app.config.js):

{
  "name": "my app",
  "plugins": [
    [
      "react-native-vision-camera",
      {
        // ...
        "enableCodeScanner": true
      }
    ]
  ]
}

Usage

To scan codes, simply create a CodeScanner instance and pass it to the <Camera>:

Hooks API

const codeScanner = useCodeScanner({
  codeTypes: ['qr', 'ean-13'],
  onCodeScanned: (codes) => {
    console.log(`Scanned ${codes.length} codes!`)
  }
})

return <Camera {...props} codeScanner={codeScanner} />

The result of this will automatically be memoized.

Imperative API

const codeScanner: CodeScanner = {
  codeTypes: ['qr', 'ean-13'],
  onCodeScanned: (codes) => {
    console.log(`Scanned ${codes.length} codes!`)
  }
}

Make sure to memoize the result of this, as every change in this will trigger a Camera session re-build.

render() {
  return <Camera {...props} codeScanner={this.codeScanner} />
}

Code result

The Code Scanner will call your onCodeScanned callback with all detected codes (Code), including their decoded string value, and their coordinates on the screen relative to subject area of the Code Scanner (the frame).

UPC-A vs EAN-13 codes

UPC-A is a special case to handle if you need to cater for it. Android's SDK officially supports UPC-A but iOS does not, instead they handle the code as EAN-13. Since EAN-13 is a superset of UPC-A, with an extra 0 digit at the front.

This means, the upc-a types are reported under the ean-13 umbrella type on iOS:

const codeScanner = useCodeScanner({
  codeTypes: ['upc-a'], // <-- ✅ We configure for 'upc-a' types
  onCodeScanned: (codes) => {
    for (const code of codes) {
      console.log(code.type); // <-- ❌ On iOS, we receive 'ean-13'
    }
  }
})

You will need to keep this in mind and do the conversion from EAN-13 to UPC-A yourself. This can be done by removing the front 0 digit from the code to get a UPC-A code.

🚀 Next section: Frame Processors