iOS的AVFoundation内置了对二维码和条形码扫描的支持。使用AVFoundation扫描二维码的功能需要几件事：
- 创建AVCaptureSession，用于捕获二维码
- 创建预览
- 捕获二维码成功后，委派回调来处理二维码的meta信息
下面的例子是基于UIViewController开发的扫描二维码Controller，使用AVCaptureMetadataOutputObjectsDelegate 获取捕获二维码图片后二维码的值
Swift 3
import AVFoundation
import UIKit
class ScannerViewController: UIViewController, AVCaptureMetadataOutputObjectsDelegate {
var captureSession: AVCaptureSession!
var previewLayer: AVCaptureVideoPreviewLayer!
override func viewDidLoad() {
super.viewDidLoad()
view.backgroundColor = UIColor.black
captureSession = AVCaptureSession()
guard let videoCaptureDevice = AVCaptureDevice.default(for: .video) else { return }
let videoInput: AVCaptureDeviceInput
do {
videoInput = try AVCaptureDeviceInput(device: videoCaptureDevice)
} catch {
return
}
if (captureSession.canAddInput(videoInput)) {
captureSession.addInput(videoInput)
} else {
failed()
return
}
let metadataOutput = AVCaptureMetadataOutput()
if (captureSession.canAddOutput(metadataOutput)) {
captureSession.addOutput(metadataOutput)
metadataOutput.setMetadataObjectsDelegate(self, queue: DispatchQueue.main)
metadataOutput.metadataObjectTypes = [.qr]
} else {
failed()
return
}
previewLayer = AVCaptureVideoPreviewLayer(session: captureSession)
previewLayer.frame = view.layer.bounds
previewLayer.videoGravity = .resizeAspectFill
view.layer.addSublayer(previewLayer)
captureSession.startRunning()
}
func failed() {
let ac = UIAlertController(title: "Scanning not supported", message: "Your device does not support scanning a code from an item. Please use a device with a camera.", preferredStyle: .alert)
ac.addAction(UIAlertAction(title: "OK", style: .default))
present(ac, animated: true)
captureSession = nil
}
override func viewWillAppear(_ animated: Bool) {
super.viewWillAppear(animated)
if (captureSession?.isRunning == false) {
captureSession.startRunning()
}
}
override func viewWillDisappear(_ animated: Bool) {
super.viewWillDisappear(animated)
if (captureSession?.isRunning == true) {
captureSession.stopRunning()
}
}
func captureOutput(_ captureOutput: AVCaptureOutput!, didOutputMetadataObjects metadataObjects: [Any]!, from connection: AVCaptureConnection!) {
captureSession.stopRunning()
if let metadataObject = metadataObjects.first {
guard let readableObject = metadataObject as? AVMetadataMachineReadableCodeObject else { return }
guard let stringValue = readableObject.stringValue else { return }
AudioServicesPlaySystemSound(SystemSoundID(kSystemSoundID_Vibrate))
found(code: stringValue)
}
dismiss(animated: true)
}
func found(code: String) {
print(code)
}
override var prefersStatusBarHidden: Bool {
return true
}
override var supportedInterfaceOrientations: UIInterfaceOrientationMask {
return .portrait
}
例子里的found()函数为自己自定义的功能。
Swift 4
升级到Swift 4后，上面代码失效了，这个主要原因是在AVCaptureMetadataOutputObjectsDelegate委派的回调函数改为了metadataOutput。
上面代码委派的回调函数
func captureOutput(_ captureOutput: AVCaptureOutput!, didOutputMetadataObjects metadataObjects: [Any]!, from connection: AVCaptureConnection!)
改为
func metadataOutput(_ output: AVCaptureMetadataOutput, didOutput metadataObjects: [AVMetadataObject], from connection: AVCaptureConnection)
注意：在Objective-C，委派的回调函数仍然是captureOutput