Fix black screen on QR scanner after first camera permission grant.

Update preview layer layout and session lifecycle when authorization completes asynchronously.

Co-authored-by: Cursor <cursoragent@cursor.com>

suixinkan/UI/Scan/QRCodeScannerViewController.swift

@@ -14,6 +14,7 @@ final class QRCodeScannerViewController: BaseViewController, AVCaptureMetadataOu
 
     private let captureSession = AVCaptureSession()
     private var previewLayer: AVCaptureVideoPreviewLayer?
+    private var isCameraConfigured = false
     private var hasHandledResult = false
 
     private let maskView = UIView()
@@ -60,17 +61,21 @@ final class QRCodeScannerViewController: BaseViewController, AVCaptureMetadataOu
         checkCameraPermission()
     }
 
+    override func viewDidAppear(_ animated: Bool) {
+        super.viewDidAppear(animated)
+        updatePreviewLayout()
+        startCaptureSessionIfNeeded()
+    }
+
     override func viewDidLayoutSubviews() {
         super.viewDidLayoutSubviews()
-        previewLayer?.frame = view.bounds
+        updatePreviewLayout()
         updateMask()
     }
 
     override func viewWillDisappear(_ animated: Bool) {
         super.viewWillDisappear(animated)
-        if captureSession.isRunning {
-            captureSession.stopRunning()
-        }
+        stopCaptureSession()
     }
 
     private func checkCameraPermission() {
@@ -94,11 +99,21 @@ final class QRCodeScannerViewController: BaseViewController, AVCaptureMetadataOu
     }
 
     private func setupCamera() {
+        if isCameraConfigured {
+            updatePreviewLayout()
+            startCaptureSessionIfNeeded()
+            return
+        }
+
         guard let device = AVCaptureDevice.default(for: .video),
               let input = try? AVCaptureDeviceInput(device: device) else {
             showToast("无法打开相机")
             return
         }
+
+        captureSession.beginConfiguration()
+        defer { captureSession.commitConfiguration() }
+
         guard captureSession.canAddInput(input) else { return }
         captureSession.addInput(input)
 
@@ -112,12 +127,30 @@ final class QRCodeScannerViewController: BaseViewController, AVCaptureMetadataOu
         layer.videoGravity = .resizeAspectFill
         view.layer.insertSublayer(layer, at: 0)
         previewLayer = layer
+        isCameraConfigured = true
 
+        updatePreviewLayout()
+        startCaptureSessionIfNeeded()
+    }
+
+    private func updatePreviewLayout() {
+        previewLayer?.frame = view.bounds
+    }
+
+    private func startCaptureSessionIfNeeded() {
+        guard isCameraConfigured, !captureSession.isRunning else { return }
         DispatchQueue.global(qos: .userInitiated).async { [weak self] in
             self?.captureSession.startRunning()
         }
     }
 
+    private func stopCaptureSession() {
+        guard captureSession.isRunning else { return }
+        DispatchQueue.global(qos: .userInitiated).async { [weak self] in
+            self?.captureSession.stopRunning()
+        }
+    }
+
     private func updateMask() {
         maskView.layer.sublayers?.forEach { $0.removeFromSuperlayer() }
         let border = CAShapeLayer()
@@ -139,7 +172,7 @@ final class QRCodeScannerViewController: BaseViewController, AVCaptureMetadataOu
               let value = object.stringValue,
               !value.isEmpty else { return }
         hasHandledResult = true
-        captureSession.stopRunning()
+        stopCaptureSession()
         onScanResult?(value)
         dismiss(animated: true)
     }