Fill in payments by scanning a QR code or picking one from photos

2026-09-20 02:00:52 +08:00
parent 399502cf72
commit c0903f4f02
8 changed files with 423 additions and 11 deletions
@@ -0,0 +1,141 @@
+import AVFoundation
+import SwiftUI
+
+/// Camera QR scanner, presented as a sheet. On a simulator (no capture device)
+/// it explains that instead of showing a dead viewfinder.
+struct QRScannerView: UIViewControllerRepresentable {
+  var onScan: (String) -> Void
+  var onCancel: () -> Void
+
+  func makeUIViewController(context: Context) -> ScannerViewController {
+    let controller = ScannerViewController()
+    controller.onScan = onScan
+    controller.onCancel = onCancel
+    return controller
+  }
+
+  func updateUIViewController(_ controller: ScannerViewController, context: Context) {}
+}
+
+final class ScannerViewController: UIViewController, AVCaptureMetadataOutputObjectsDelegate {
+  var onScan: ((String) -> Void)?
+  var onCancel: (() -> Void)?
+
+  private let session = AVCaptureSession()
+  private var previewLayer: AVCaptureVideoPreviewLayer?
+  private var hasScanned = false
+  private var messageLabel: UILabel?
+
+  override func viewDidLoad() {
+    super.viewDidLoad()
+    view.backgroundColor = .black
+
+    let cancel = UIButton(type: .system)
+    cancel.setTitle("Cancel", for: .normal)
+    cancel.setTitleColor(.white, for: .normal)
+    cancel.titleLabel?.font = .systemFont(ofSize: 16, weight: .semibold)
+    cancel.addTarget(self, action: #selector(cancelTapped), for: .touchUpInside)
+    cancel.translatesAutoresizingMaskIntoConstraints = false
+    view.addSubview(cancel)
+    NSLayoutConstraint.activate([
+      cancel.topAnchor.constraint(equalTo: view.safeAreaLayoutGuide.topAnchor, constant: 12),
+      cancel.leadingAnchor.constraint(equalTo: view.leadingAnchor, constant: 20),
+    ])
+
+    let label = UILabel()
+    label.numberOfLines = 0
+    label.textAlignment = .center
+    label.textColor = .white
+    label.font = .systemFont(ofSize: 14)
+    label.translatesAutoresizingMaskIntoConstraints = false
+    view.addSubview(label)
+    NSLayoutConstraint.activate([
+      label.centerYAnchor.constraint(equalTo: view.centerYAnchor),
+      label.leadingAnchor.constraint(equalTo: view.leadingAnchor, constant: 32),
+      label.trailingAnchor.constraint(equalTo: view.trailingAnchor, constant: -32),
+    ])
+    messageLabel = label
+
+    requestCamera()
+  }
+
+  override func viewDidLayoutSubviews() {
+    super.viewDidLayoutSubviews()
+    previewLayer?.frame = view.bounds
+  }
+
+  override func viewWillDisappear(_ animated: Bool) {
+    super.viewWillDisappear(animated)
+    if session.isRunning { session.stopRunning() }
+  }
+
+  @objc private func cancelTapped() {
+    onCancel?()
+  }
+
+  private func requestCamera() {
+    guard let device = AVCaptureDevice.default(for: .video) else {
+      showMessage("This device has no camera. Use “Photo” to pick a QR from the library instead.")
+      return
+    }
+
+    switch AVCaptureDevice.authorizationStatus(for: .video) {
+    case .authorized:
+      configure(device: device)
+    case .notDetermined:
+      AVCaptureDevice.requestAccess(for: .video) { [weak self] granted in
+        DispatchQueue.main.async {
+          if granted {
+            self?.configure(device: device)
+          } else {
+            self?.showMessage("Camera access is off. Enable it in Settings, or use “Photo”.")
+          }
+        }
+      }
+    default:
+      showMessage("Camera access is off. Enable it in Settings, or use “Photo”.")
+    }
+  }
+
+  private func configure(device: AVCaptureDevice) {
+    guard let input = try? AVCaptureDeviceInput(device: device), session.canAddInput(input) else {
+      showMessage("The camera could not be started. Use “Photo” instead.")
+      return
+    }
+    session.addInput(input)
+
+    let output = AVCaptureMetadataOutput()
+    guard session.canAddOutput(output) else {
+      showMessage("The camera could not be started. Use “Photo” instead.")
+      return
+    }
+    session.addOutput(output)
+    output.setMetadataObjectsDelegate(self, queue: .main)
+    output.metadataObjectTypes = [.qr]
+
+    let layer = AVCaptureVideoPreviewLayer(session: session)
+    layer.videoGravity = .resizeAspectFill
+    layer.frame = view.bounds
+    view.layer.insertSublayer(layer, at: 0)
+    previewLayer = layer
+
+    DispatchQueue.global(qos: .userInitiated).async { [weak self] in
+      self?.session.startRunning()
+    }
+  }
+
+  private func showMessage(_ text: String) {
+    messageLabel?.text = text
+  }
+
+  func metadataOutput(_ output: AVCaptureMetadataOutput,
+                      didOutput metadataObjects: [AVMetadataObject],
+                      from connection: AVCaptureConnection) {
+    guard !hasScanned else { return }
+    guard let object = metadataObjects.first as? AVMetadataMachineReadableCodeObject,
+          let value = object.stringValue, !value.isEmpty else { return }
+    hasScanned = true
+    session.stopRunning()
+    onScan?(value)
+  }
+}