USB 摄像头适配iPadOS17+ios端的配置

packages/usb_camera_android/ios/Classes/UsbCameraView.swift

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+//
+//  UsbCameraView.swift
+//  usb_camera_android
+//
+//  iOS 原生预览 PlatformView：用 AVCaptureVideoPreviewLayer 直接渲染 session。
+//
+
+import AVFoundation
+import Flutter
+import UIKit
+
+/// 以 AVCaptureVideoPreviewLayer 作为 backing layer 的 UIView。
+final class UsbCameraPreviewUIView: UIView {
+    override class var layerClass: AnyClass { AVCaptureVideoPreviewLayer.self }
+    var previewLayer: AVCaptureVideoPreviewLayer {
+        return layer as! AVCaptureVideoPreviewLayer
+    }
+}
+
+final class UsbCameraView: NSObject, FlutterPlatformView {
+    private let previewView: UsbCameraPreviewUIView
+
+    init(engine: UsbCameraEngine, frame: CGRect) {
+        self.previewView = UsbCameraPreviewUIView(frame: frame)
+        super.init()
+        previewView.previewLayer.session = engine.captureSession
+        previewView.previewLayer.videoGravity = .resizeAspect
+    }
+
+    func view() -> UIView {
+        return previewView
+    }
+}
+
+final class UsbCameraViewFactory: NSObject, FlutterPlatformViewFactory {
+    private let engine: UsbCameraEngine
+
+    init(engine: UsbCameraEngine) {
+        self.engine = engine
+        super.init()
+    }
+
+    func createArgsCodec() -> FlutterMessageCodec & NSObjectProtocol {
+        return FlutterStandardMessageCodec.sharedInstance()
+    }
+
+    func create(withFrame frame: CGRect, viewIdentifier viewId: Int64,
+                arguments args: Any?) -> FlutterPlatformView {
+        return UsbCameraView(engine: engine, frame: frame)
+    }
+}