I am using the react-qr-reader component to build a qr scanner modal for my website.

The modal is created as expected and I can scan different qr codes but after dismissing the ion-modal the scanner keeps the users camera active but stops detecting qr codes.

How can I deactivate the users camera?

In my research I found the following question already asked. There the close function I am using is proposed with

ref.current.stopCamera()

at the end. Somehow I can not define ref because ref is not in "IntrinsicAttributes & QrReaderProps" of the QrReader component.

So, how can I reference the react component and is the close function with the added

ref.current.stopCamera()

the correct way of deactivation the camera?

Thanks for your help!

Here is my code:

export const ScannerModal: React.FC<ScannerProps> = ({ triggerID, handleScannedNode }) => {
  const modal = useRef<HTMLIonModalElement>(null);
  const scannerConstraints: MediaTrackConstraints = {

  }

  function onDissMiss(event: CustomEvent<OverlayEventDetail>){
    console.log(event)
    close()
  }

  function handleScan(result: string){
    close()
    handleScannedNode(result)
  }

  async function close(){
    console.log("closing")
    const stream = await navigator.mediaDevices.getUserMedia({
      audio: false,
      video: true,
  });
  stream.getTracks().forEach(function (track) {
      track.stop();
      track.enabled = false;
  });
  //ref.current.stopCamera()
  }

  return (
  <>
  <IonModal trigger={triggerID} onWillDismiss={onDissMiss} ref={modal}>
    <IonTitle>Scanne einen QR-Code</IonTitle>
    <IonPage>
    <QrReader constraints={scannerConstraints} ref={}
        onResult={(result, error) => {
          if (!!result) {
            handleScan(result?.getText());
          }

          if (!!error) {
            //console.info(error);
          }
        }}/>
    </IonPage>
  </IonModal>
  </>
  );
};

I tried referencing the QrReader component via:

const reader = useRef(null);

<QrReader constraints={scannerConstraints} ref={reader}
        onResult={(result, error) => {
          if (!!result) {
            handleScan(result?.getText());
          }

          if (!!error) {
            //console.info(error);
          }
        }}/>

The error I received was:

Property 'ref' does not exist on type 'IntrinsicAttributes & QrReaderProps'.

CodePudding user response：

access the ref, you can use the useRef hook in your component

const reader = useRef(null);

<QrReader constraints={scannerConstraints} ref={reader}
        onResult={(result, error) => {
          if (!!result) {
            handleScan(result?.getText());
          }

          if (!!error) {
            //console.info(error);
          }
        }}/>

Then, you can stop the camera when you want to close the modal by calling the stopCamera method on the ref.

function close(){
  console.log("closing")
  reader.current.stopCamera();
}

CodePudding user response：

For everybody finding this thread wanting to just implement a simple react qr scanner:

I found a working solution using this qr-scanner project.

I build my component like this:

import { useRef, useState, useEffect } from 'react';   
import { IonModal, IonPage, IonTitle } from '@ionic/react';
import { OverlayEventDetail } from '@ionic/core'; 
import QrScanner from 'qr-scanner';

interface ScannerProps {
  triggerID: string;
}

const QrModal: React.FC<ScannerProps> = ({ triggerID }) => {
  const modal = useRef<HTMLIonModalElement>(null);
  const video = useRef<HTMLVideoElement>(null);
  const [qrScanner, setQrScanner] = useState<QrScanner>();

  function onDissMiss(_event: CustomEvent<OverlayEventDetail>) {
    close();
  }

  function handleScan(result: QrScanner.ScanResult) {
    //Logic with scanned qr code
  }

  async function close() {
    qrScanner?.stop();
    qrScanner?.destroy();
    setQrScanner(undefined);
  }

  useEffect(() => {
    if (video.current) {
      const qrScanner = new QrScanner(video.current, (result) => handleScan(result), {
        highlightScanRegion: true,
      });
      qrScanner.start();
      setQrScanner(qrScanner);
    }
    // Dependency array missing handleScan, since it should not set Scanner on handleScan change
    // eslint-disable-next-line
  }, [video.current]);

  return (
    <>
      <IonModal trigger={triggerID} onWillDismiss={onDissMiss} ref={modal}>
        <IonTitle>Scan your QR-Code</IonTitle>
        <IonPage>
          <video ref={video}></video>
        </IonPage>
      </IonModal>
    </>
  );
};

export default QrModal;