如何在AVcapture会话中启动动作

Question

I wrote a code for scanning barcodes. I want to display a view when a barcode has been scanned. This is my barcode scanner code

    func captureOutput(_ captureOutput: AVCaptureOutput!, didOutputMetadataObjects metadataObjects: [Any]!, from connection: AVCaptureConnection!) {

    // Check if the metadataObjects array is not nil and it contains at least one object.
    if metadataObjects == nil || metadataObjects.count == 0 {
        qrCodeFrameView?.frame = CGRect.zero
        messageLabel.text = "No QR/barcode is detected"
        return
    }
    //Get metadata object
    let metadataObj = metadataObjects[0] as! AVMetadataMachineReadableCodeObject
    if supportedCodeTypes.contains(metadataObj.type) {
        //if the found metadata is equal to the QR code metadata then update the status label's text and set the the bounds
        let barCodeObject = videoPreviewLayer?.transformedMetadataObject(for: metadataObj)
        qrCodeFrameView?.frame = barCodeObject!.bounds

        if metadataObj.stringValue != nil {
            var productbarcode = metadataObj.stringValue
            messageLabel.text = productbarcode
            print("Barcode detected")

        }
    }
}

The view I want to display is setup in func Setupproductcontainer() . It works fine when I add it to viewDidLoad but I don't want it to display until a barcode is detected. So I tried adding Setupproductcontainer() under the print("Barcode detected") statement but nothing happens. how can I initiate the Setupproductcontainer() when the barcode is detected?

Answer 1

It's possible that you are trying to make a UI change on a background thread.

I suggest you call your function inside a DispatchQueue.main code block to run it on the main thread. The reason you should do this is every change made on the UI should be done in the main thread. If you try to change it in a background thread nothing will happen.

DispatchQueue.main.async {
    self.Setupproductcontainer() 
}