Zxing js how to stop scanning properly

[FFParf]

I am integrating Zxing js to my web application. To stop the camera i am calling codeReader.Reset()

But that gives me this error(when i call it before scanning any codes): 'Video stream has ended before any code could be detected.'

My question is, is codeReader.Reset() the right way to stop the scanner/video? and what to do about that error?

Thanks in advance.

[nperepichka]

I have same issue...

[zacharytyhacz]

Hello @FFParf , I have a couple questions about your situation:

• Which code reader module of the package are you using? ( PDF417, QRcode, etc )
• Are you using the codeReader.decodeOnceFromVideoDevice() and codeReader.listVideoInputDevices() methods?

I've used these methods before with PDF417 and they turn off the stream correctly for me. However, yes, that message still shows as a warning for me. But also keep in mind that your browser will persist the camera permission for that page's tab, making it seem like it's still on.

[anton-kirschhock]

Got the same issue when using the Angular component library, but I do think that the issue is in the core library.
Also note that the little LED of my webcam stays on and the camera cannot be used by another program except the website.
I am using Chrome on Windows 10.
Note that this does do work in the Edge Chromium version sometimes... Any ideas?

[KlausHans]

Got the same issue in Angular.
Here is my piece of test code

    this.codeReader = new BrowserMultiFormatReader();
    this.codeReader.listVideoInputDevices()
      .then((videoDeviceList: MediaDeviceInfo[]) => {
        console.log("videoDeviceList", videoDeviceList);
        this.moreThanOneCamera = videoDeviceList.length > 1;
        this.changeDetector.detectChanges();
        this.videoDeviceId = this.localStorageService.getStorageItem<string>(LocalStorageKey.ScanVideoDeviceId);

        this.codeReader.decodeOnceFromVideoDevice(this.videoDeviceId, 'video')
          .then(result => console.log(result))
          .catch(err => console.log(err));
      })
      .catch(err => console.log(err));

If i do nothing in ngOnDestroy() the camerastream is still open if the component is destroyed (before any code is scanned). If i call this.codeReader.reset(); in ngOnDestroy() i get the error NotFoundException: Video stream has ended before any code could be detected. but now the stream is closed properly.
Browser: Firefox 81

[odahcam]

@KlausHans your method is not wrong, you just need to wrap that reset call in a try-catch block so it can [oddly] inform you with exceptions if something didn't endup as expected. This expcetions throw confuses everyone and I'm looking forward to change it.

[odahcam]

Hey guys, take a look on the new browser layer: https://github.com/zxing-js/browser

It features way better scan handling and allows you to stop the continuous scan by simply calling a function received from each continuous decode call. That means we can have now multiple continuous scans running for multiple devices, or videos, etc. As I said, way better scan handling.

[tdelam]

What if we don't want to stop controls after a scan but want to use a lifecycle method such as when a component is unmounting or in stimulus disconnect()?