我试图让应用程序在ios 10和Swift 3中扫描QR码。但是，我的QRScannerController无法检测到QR码但显示了摄像头视图。
我不明白代码有什么问题。这是控制器的实现：
import UIKit
import AVFoundation
class QRScannerController: UIViewController, AVCaptureMetadataOutputObjectsDelegate {
@IBOutlet var messageLabel:UILabel!
@IBOutlet var topbar: UIView!
//TESTING
var captureSession: AVCaptureSession?
var videoPreviewLayer: AVCaptureVideoPreviewLayer?
var qrCodeFrameView: UIView?
override func viewDidLoad() {
super.viewDidLoad()
// Do any additional setup after loading the view.
// Get an instance of the AVCaptureDevice class to initialize a device object and provide the video as the media type parameter
let captureDevice = AVCaptureDevice.defaultDevice(withMediaType: AVMediaTypeVideo)
do {
view.bringSubview(toFront: messageLabel)
view.bringSubview(toFront: topbar)
// Get an instance of the AVCaptureDeviceInput class using the previous deivce object
let input = try AVCaptureDeviceInput(device: captureDevice)
// Initialize the captureSession object
captureSession = AVCaptureSession()
// Set the input devcie on the capture session
captureSession?.addInput(input)
// Initialize a AVCaptureMetadataOutput object and set it as the input device
let captureMetadataOutput = AVCaptureMetadataOutput()
captureSession?.addOutput(captureMetadataOutput)
// Set delegate and use the default dispatch queue to execute the call back
captureMetadataOutput.setMetadataObjectsDelegate(self, queue: DispatchQueue.main)
captureMetadataOutput.metadataObjectTypes = [AVMetadataObjectTypeQRCode]
//Initialise the video preview layer and add it as a sublayer to the viewPreview view's layer
videoPreviewLayer = AVCaptureVideoPreviewLayer(session: captureSession)
videoPreviewLayer?.videoGravity = AVLayerVideoGravityResizeAspectFill
videoPreviewLayer?.frame = view.layer.bounds
view.layer.addSublayer(videoPreviewLayer!)
//start video capture
captureSession?.startRunning()
//Initialize QR Code Frame to highlight the QR code
qrCodeFrameView = UIView()
if let qrCodeFrameView = qrCodeFrameView {
qrCodeFrameView.layer.borderColor = UIColor.green.cgColor
qrCodeFrameView.layer.borderWidth = 2
view.addSubview(qrCodeFrameView)
view.bringSubview(toFront: qrCodeFrameView)
}
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 code is detected"
return
}
// Get the metadata object.
let metadataObj = metadataObjects[0] as! AVMetadataMachineReadableCodeObject
if metadataObj.type == AVMetadataObjectTypeQRCode {
// If the found metadata is equal to the QR code metadata then update the status label's text and set the bounds
let barCodeObject = videoPreviewLayer?.transformedMetadataObject(for: metadataObj)
qrCodeFrameView?.frame = barCodeObject!.bounds
if metadataObj.stringValue != nil {
messageLabel.text = metadataObj.stringValue
}
}
}
} catch {
//If any error occurs, simply print it out
print(error)
return
}
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// Dispose of any resources that can be recreated.
}