iOS Swift 条码读取

Question

我的应用程序中有条码扫描功能。检测到条形码后，我停止捕获会话以允许处理条形码。但是，在处理完条形码后，我希望扫描控制器保持正常状态并扫描下一个条形码。我曾假设启动捕获会话（startRunning（））会这样做，但图像保持冻结状态。如何重新开始捕获会话？

Answer 1

要停止会话，请使用此代码

self.session.stopRunning()

要重新开始，请使用此代码

self.session.startRunning()

这是实现条码扫描器的所有代码...

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

为 swift 2.0 编辑了上述代码：

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 版本：

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更新

 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
  }