iOS Swift Barcode Reading - ios

Question

I have barcode scanning working in my app. After the barcode is detected I stop the capture session to allow processing of the barcode. However, after the barcode is processed I want the scanning controller to stay up and the next barcode scanned. I had assumed that starting the capture session (startRunning()) would do it but the image stays frozen. How can I start the capture session again?

Answer 1

To Stop The Session use this code
self.session.stopRunning()
To begin it agian, use this code
self.session.startRunning()
Here is all the code to implement a barcode scanner...
import UIKit
import AVFoundation
class ViewController: UIViewController, AVCaptureMetadataOutputObjectsDelegate {
let session : AVCaptureSession = AVCaptureSession()
var previewLayer : AVCaptureVideoPreviewLayer!
var highlightView : UIView = UIView()
override func viewDidLoad() {
super.viewDidLoad()
// Allow the view to resize freely
self.highlightView.autoresizingMask =
UIViewAutoresizing.FlexibleTopMargin |
UIViewAutoresizing.FlexibleBottomMargin |
UIViewAutoresizing.FlexibleLeftMargin |
UIViewAutoresizing.FlexibleRightMargin
// Select the color you want for the completed scan reticle
self.highlightView.layer.borderColor = UIColor.greenColor().CGColor
self.highlightView.layer.borderWidth = 3
// Add it to our controller's view as a subview.
self.view.addSubview(self.highlightView)
// For the sake of discussion this is the camera
let device = AVCaptureDevice.defaultDeviceWithMediaType(AVMediaTypeVideo)
// Create a nilable NSError to hand off to the next method.
// Make sure to use the "var" keyword and not "let"
var error : NSError? = nil
let input : AVCaptureDeviceInput? =
AVCaptureDeviceInput.deviceInputWithDevice(device, error: &error)
as? AVCaptureDeviceInput
// If our input is not nil then add it to the session, otherwise we're kind of done!
if input != nil {
session.addInput(input)
} else {
// This is fine for a demo, do something real with this in your app. :)
println(error)
}
let output = AVCaptureMetadataOutput()
output.setMetadataObjectsDelegate(self, queue: dispatch_get_main_queue())
session.addOutput(output)
output.metadataObjectTypes = output.availableMetadataObjectTypes
previewLayer =
AVCaptureVideoPreviewLayer.layerWithSession(session)
as! AVCaptureVideoPreviewLayer
previewLayer.frame = self.view.bounds
previewLayer.videoGravity = AVLayerVideoGravityResizeAspectFill
self.view.layer.addSublayer(previewLayer)
// Start the scanner. You'll have to end it yourself later.
session.startRunning()
}
// This is called when we find a known barcode type with the camera.
func captureOutput(
captureOutput: AVCaptureOutput!,
didOutputMetadataObjects metadataObjects: [AnyObject]!,
fromConnection connection: AVCaptureConnection!) {
var highlightViewRect = CGRectZero
var barCodeObject : AVMetadataObject!
var detectionString : String!
let barCodeTypes = [AVMetadataObjectTypeUPCECode,
AVMetadataObjectTypeCode39Code,
AVMetadataObjectTypeCode39Mod43Code,
AVMetadataObjectTypeEAN13Code,
AVMetadataObjectTypeEAN8Code,
AVMetadataObjectTypeCode93Code,
AVMetadataObjectTypeCode128Code,
AVMetadataObjectTypePDF417Code,
AVMetadataObjectTypeQRCode,
AVMetadataObjectTypeAztecCode]
// The scanner is capable of capturing multiple 2-dimensional barcodes in one scan.
for metadata in metadataObjects {
for barcodeType in barCodeTypes {
if metadata.type == barcodeType {
barCodeObject = self.previewLayer.transformedMetadataObjectForMetadataObject(metadata as! AVMetadataMachineReadableCodeObject)
highlightViewRect = barCodeObject.bounds
detectionString = (metadata as! AVMetadataMachineReadableCodeObject).stringValue
self.session.stopRunning()
self.alert(detectionString)
break
}
}
}
println(detectionString)
self.highlightView.frame = highlightViewRect
self.view.bringSubviewToFront(self.highlightView)
}
func alert(Code: String){
let actionSheet:UIAlertController =
UIAlertController(
title: "Barcode",
message: "\(Code)",
preferredStyle: UIAlertControllerStyle.Alert)
// for alert add .Alert instead of .Action Sheet
// start copy
let firstAlertAction:UIAlertAction =
UIAlertAction(
title: "OK",
style: UIAlertActionStyle.Default,
handler: { (alertAction: UIAlertAction!) in
// action when pressed
self.session.startRunning()
})
actionSheet.addAction(firstAlertAction)
// end copy
self.presentViewController(actionSheet, animated: true, completion: nil)
}
}

Answer 2

edited the above code for swift 2.0:
import UIKit
import AVFoundation
class BarCodeViewController: UIViewController, AVCaptureMetadataOutputObjectsDelegate {
let session : AVCaptureSession = AVCaptureSession()
var previewLayer : AVCaptureVideoPreviewLayer!
#IBOutlet weak var highlightView: UIView!
override func viewDidLoad() {
super.viewDidLoad()
// Select the color you want for the completed scan reticle
self.highlightView.layer.borderColor = UIColor.greenColor().CGColor
self.highlightView.layer.borderWidth = 3
// Add it to our controller's view as a subview.
self.view.addSubview(self.highlightView)
// For the sake of discussion this is the camera
let device = AVCaptureDevice.defaultDeviceWithMediaType(AVMediaTypeVideo)
// Create a nilable NSError to hand off to the next method.
// Make sure to use the "var" keyword and not "let"
var error : NSError? = nil
var input: AVCaptureDeviceInput = AVCaptureDeviceInput()
do {
input = try AVCaptureDeviceInput(device: device) as AVCaptureDeviceInput
} catch let myJSONError {
print(myJSONError)
}
// If our input is not nil then add it to the session, otherwise we're kind of done!
if input != AVCaptureDeviceInput() {
session.addInput(input)
}
else {
// This is fine for a demo, do something real with this in your app. :)
print(error)
}
let output = AVCaptureMetadataOutput()
output.setMetadataObjectsDelegate(self, queue: dispatch_get_main_queue())
session.addOutput(output)
output.metadataObjectTypes = output.availableMetadataObjectTypes
previewLayer = AVCaptureVideoPreviewLayer(session: session)
previewLayer.frame = self.view.bounds
previewLayer.videoGravity = AVLayerVideoGravityResizeAspectFill
self.view.layer.addSublayer(previewLayer)
// Start the scanner. You'll have to end it yourself later.
session.startRunning()
}
// This is called when we find a known barcode type with the camera.
func captureOutput(captureOutput: AVCaptureOutput!, didOutputMetadataObjects metadataObjects: [AnyObject]!, fromConnection connection: AVCaptureConnection!) {
var highlightViewRect = CGRectZero
var barCodeObject : AVMetadataObject!
var detectionString : String!
let barCodeTypes = [AVMetadataObjectTypeUPCECode,
AVMetadataObjectTypeCode39Code,
AVMetadataObjectTypeCode39Mod43Code,
AVMetadataObjectTypeEAN13Code,
AVMetadataObjectTypeEAN8Code,
AVMetadataObjectTypeCode93Code,
AVMetadataObjectTypeCode128Code,
AVMetadataObjectTypePDF417Code,
AVMetadataObjectTypeQRCode,
AVMetadataObjectTypeAztecCode
]
// The scanner is capable of capturing multiple 2-dimensional barcodes in one scan.
for metadata in metadataObjects {
for barcodeType in barCodeTypes {
if metadata.type == barcodeType {
barCodeObject = self.previewLayer.transformedMetadataObjectForMetadataObject(metadata as! AVMetadataMachineReadableCodeObject)
highlightViewRect = barCodeObject.bounds
detectionString = (metadata as! AVMetadataMachineReadableCodeObject).stringValue
self.session.stopRunning()
self.alert(detectionString)
break
}
}
}
print(detectionString)
self.highlightView.frame = highlightViewRect
self.view.bringSubviewToFront(self.highlightView)
}
func alert(Code: String){
let actionSheet:UIAlertController = UIAlertController(title: "Barcode", message: "\(Code)", preferredStyle: UIAlertControllerStyle.Alert)
// for alert add .Alert instead of .Action Sheet
// start copy
let firstAlertAction:UIAlertAction = UIAlertAction(title: "OK", style: UIAlertActionStyle.Default, handler: {
(alertAction:UIAlertAction!) in
// action when pressed
self.session.startRunning()
})
actionSheet.addAction(firstAlertAction)
// end copy
self.presentViewController(actionSheet, animated: true, completion: nil)
}
}

Answer 3

Swift 3.0 version:
import UIKit
import AVFoundation
class BarCodeViewController: UIViewController, AVCaptureMetadataOutputObjectsDelegate {
let session : AVCaptureSession = AVCaptureSession()
var previewLayer : AVCaptureVideoPreviewLayer!
#IBOutlet weak var highlightView: UIView!
override func viewDidLoad() {
super.viewDidLoad()
self.highlightView.layer.borderColor = UIColor.green.cgColor
self.highlightView.layer.borderWidth = 3
// Add it to our controller's view as a subview.
self.view.addSubview(self.highlightView)
// For the sake of discussion this is the camera
let device = AVCaptureDevice.defaultDevice(withMediaType: AVMediaTypeVideo)
// Create a nilable NSError to hand off to the next method.
// Make sure to use the "var" keyword and not "let"
var error : NSError? = nil
var input: AVCaptureDeviceInput = AVCaptureDeviceInput()
do {
input = try AVCaptureDeviceInput(device: device) as AVCaptureDeviceInput
} catch let myJSONError {
print(myJSONError)
}
// If our input is not nil then add it to the session, otherwise we're kind of done!
if input != AVCaptureDeviceInput() {
session.addInput(input)
}
else {
// This is fine for a demo, do something real with this in your app. :)
print(error!)
}
let output = AVCaptureMetadataOutput()
output.setMetadataObjectsDelegate(self, queue: DispatchQueue.main)
session.addOutput(output)
output.metadataObjectTypes = output.availableMetadataObjectTypes
previewLayer = AVCaptureVideoPreviewLayer(session: session)
previewLayer.frame = self.view.bounds
previewLayer.videoGravity = AVLayerVideoGravityResizeAspectFill
self.view.layer.addSublayer(previewLayer)
// Start the scanner. You'll have to end it yourself later.
session.startRunning()
}
// This is called when we find a known barcode type with the camera.
#nonobjc func captureOutput(
captureOutput: AVCaptureOutput!,
didOutputMetadataObjects metadataObjects: [AnyObject]!,
fromConnection connection: AVCaptureConnection!) {
var highlightViewRect = CGRect()
var barCodeObject : AVMetadataObject!
var detectionString : String!
let barCodeTypes = [AVMetadataObjectTypeUPCECode,
AVMetadataObjectTypeCode39Code,
AVMetadataObjectTypeCode39Mod43Code,
AVMetadataObjectTypeEAN13Code,
AVMetadataObjectTypeEAN8Code,
AVMetadataObjectTypeCode93Code,
AVMetadataObjectTypeCode128Code,
AVMetadataObjectTypePDF417Code,
AVMetadataObjectTypeQRCode,
AVMetadataObjectTypeAztecCode]
// The scanner is capable of capturing multiple 2-dimensional barcodes in one scan.
for metadata in metadataObjects {
for barcodeType in barCodeTypes {
if metadata.type == barcodeType {
barCodeObject = self.previewLayer.transformedMetadataObject(for: metadata as! AVMetadataMachineReadableCodeObject)
highlightViewRect = barCodeObject.bounds
detectionString = (metadata as! AVMetadataMachineReadableCodeObject).stringValue
self.session.stopRunning()
self.alert(Code: detectionString)
break
}
}
}
print(detectionString)
self.highlightView.frame = highlightViewRect
self.view.bringSubview(toFront: self.highlightView)
}
func alert(Code: String){
let actionSheet:UIAlertController = UIAlertController(title: "Barcode", message: "\(Code)", preferredStyle: UIAlertControllerStyle.alert)
// for alert add .Alert instead of .Action Sheet
// start copy
let firstAlertAction:UIAlertAction = UIAlertAction(title: "OK", style: UIAlertActionStyle.default, handler: { (alertAction: UIAlertAction!) in
// action when pressed
self.session.startRunning()
})
actionSheet.addAction(firstAlertAction)
// end copy
self.present(actionSheet, animated: true, completion: nil)
}
}

Answer 4

Swift 5 update
func captureOutput(
captureOutput: AVCaptureOutput,
didOutputMetadataObjects metadataObjects: [AnyObject],
fromConnection connection: AVCaptureConnection,
barCodeType: [AVMetadataObject.ObjectType]) -> String? {
var detectionString: String?
var highlightViewRect = CGRect()
let barCodeTypes = barCodeType
if let metadataObject = metadataObjects.first {
for barcodeType in barCodeTypes {
if metadataObject.type == barcodeType {
guard let readableObject = metadataObject as? AVMetadataMachineReadableCodeObject else { return String()}
guard let barCodeObject = self.previewLayer.transformedMetadataObject(for: readableObject) else { return String()}
highlightViewRect = barCodeObject.bounds
detectionString = readableObject.stringValue
self.captureSession.stopRunning()
break
}
}
}
self.qrView.frame = highlightViewRect
self.view.bringSubviewToFront(self.qrView)
return detectionString
}