kernel/media

useSmartScanner() — one API for QR codes, barcodes, and document scanning, backed by each platform’s real, ready-made scanner UI instead of a custom camera view built from scratch.


import { useSmartScanner } from 'react-native-kernel/media';

This is the second (and last) deliberate native-dependency exception, and it’s Android-only: Google Play Services (ML Kit’s GmsBarcodeScanning and GmsDocumentScanning), for the same reason as kernel/auth’s biometric prompt — there’s no dependency-free way to get a polished, ready-made scanner UI. iOS needs nothing extra: QR/barcode scanning is built on AVCaptureMetadataOutput and document scanning on VisionKit’s VNDocumentCameraViewController, both system frameworks.

`useSmartScanner()`


import { useSmartScanner } from 'react-native-kernel/media';
 
function ScanButton() {
  const scanner = useSmartScanner();
 
  const scanQr = async () => {
    const result = await scanner.scan('qr');
    if (result.cancelled) return;
    console.log(result.format, result.value); // 'QR_CODE', 'https://...'
  };
 
  const scanDoc = async () => {
    const result = await scanner.scan('document');
    if (result.cancelled) return;
    console.log(result.imageUris); // ['file:///.../page1.jpg']
  };
 
  return <Button title="Scan QR" onPress={scanQr} disabled={scanner.isScanning} />;
}

mode is one of 'qr' | 'barcode' | 'document'. Every call presents a full-screen system UI — Google’s own code-scanner sheet on Android, or a live AVCaptureMetadataOutput view / VNDocumentCameraViewController on iOS — and resolves once the user finishes or cancels.

Return value

Field	Type	Notes
`isScanning`	`boolean`
`error`	`Error \| null`	Set (and rethrown) when `scan()` rejects
`isAvailable(mode)`	`(ScanMode) => Promise<boolean>`	Checks without showing any UI
`scan(mode)`	`(ScanMode) => Promise<ScanResult>`

`ScanResult`


interface ScanResult {
  cancelled: boolean;
  value?: string;       // decoded text — 'qr' / 'barcode' only
  format?: string;       // e.g. 'QR_CODE', 'EAN_13' — 'qr' / 'barcode' only
  imageUris?: string[]; // file:// URIs, in page order — 'document' only
}

A user backing out of the scanner resolves { cancelled: true } — it never throws for a cancel, only for a real failure (e.g. no camera available).

No camera means scan() rejects, not crashes. Both qr/barcode and document modes check for camera hardware before presenting anything — this matters concretely on the iOS Simulator, which has no camera: scan('qr') there rejects with no_camera instead of presenting a scanner view with nothing to show. (An earlier version of this module didn’t check first, and calling dismissViewControllerAnimated: from inside viewDidLoad — before the presentation transition finished — crashed the app outright.) Always wrap scan() in a try/catch, or check isAvailable(mode) first.

Android: first run may show a Play Services update

The first time a device uses GmsBarcodeScanning or GmsDocumentScanning, Play Services may need to download or update its own module before showing the scanner — you’ll briefly see Google’s own “Downloading updates to Google Play services…” screen. This is normal, one-time, and outside this package’s control; subsequent scans are instant.

Permissions

See Installation for the camera (and, for document scanning, no extra permission beyond camera) entries each platform needs.

Next: kernel/picker.