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import 'dart:async';
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import 'package:flutter/material.dart';
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import 'package:pj_supermarket_cloud/common/models/plugs/face_recognition_session_models.dart';
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import 'package:pj_supermarket_cloud/common/utils/plugs/face_discern_plugs.dart';
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import 'package:pj_supermarket_cloud/common/widgets/face/face_camera_preview.dart';
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/// 主副屏共用的常驻人脸摄像头预览。
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///
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/// 组件只持有当前 Flutter Engine 的 Texture 和原生状态订阅，不创建、结束或重试
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/// 业务识别 Session，因此查询结果展示的十秒内仍能保持实时画面。
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class FaceLiveCameraPreview extends StatefulWidget {
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/// 创建跟随宿主页面生命周期的实时预览区域。
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const FaceLiveCameraPreview({
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super.key,
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required this.statusText,
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required this.statusColor,
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this.scale = 1,
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});
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/// 查询状态对应的可见文案，避免原生空闲态被误解为仍在识别下一位。
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final String statusText;
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/// 查询状态对应的语义颜色，必须与文字同时表达状态。
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final Color statusColor;
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/// 宿主 Engine 自己计算的尺寸比例，默认按 1920 x 1080 设计尺寸一比一展示。
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final double scale;
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/// 创建当前 Flutter Engine 的 Texture 生命周期状态。
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@override
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State<FaceLiveCameraPreview> createState() => _FaceLiveCameraPreviewState();
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}
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/// [FaceLiveCameraPreview] 的 Texture、原生事件和异常状态所有者。
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class _FaceLiveCameraPreviewState extends State<FaceLiveCameraPreview> {
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/// 当前 Flutter Engine 持有的原生预览纹理。
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FaceRecognitionPreviewTexture? _texture;
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/// 最近一次原生人脸会话事件，用于方向、人脸框和设备状态渲染。
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FaceRecognitionSessionEvent? _event;
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/// 常驻原生会话事件订阅，页面销毁时必须取消。
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StreamSubscription<FaceRecognitionSessionEvent>? _eventSubscription;
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/// Texture 异步创建序号，用于释放页面销毁或重建后迟到的旧资源。
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int _textureRequestId = 0;
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/// 当前预览初始化失败信息；为空表示按 Texture 和原生状态正常展示。
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String? _previewError;
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/// 订阅原生状态并创建当前 Engine 独立的输出 Texture。
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@override
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void initState() {
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super.initState();
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_eventSubscription = FaceDiscernPlugs.sessionStream.listen(
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_handleEvent,
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onError: _handleEventError,
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);
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unawaited(_loadInitialState());
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unawaited(_initializeTexture());
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}
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/// 读取挂载前已存在的热摄像头状态，避免页面刚进入时长期停留在初始化提示。
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Future<void> _loadInitialState() async {
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try {
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final event = await FaceDiscernPlugs.getRecognitionState();
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// EventChannel 可能先送达真实检测帧；迟到的 MethodChannel 快照不含 faceBoxes，
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// 只能用于尚未收到任何事件的首次占位，不能把已经显示的人脸框清空。
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if (mounted && _event == null) setState(() => _event = event);
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} catch (_) {
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// 后续 EventChannel 仍可恢复状态，首次快照失败不覆盖真实 Texture 画面。
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}
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}
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/// 更新最近原生状态；致命失败后的冷重试需要替换已经失效的 Renderer 输出。
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void _handleEvent(FaceRecognitionSessionEvent event) {
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if (!mounted || !_shouldAcceptEvent(event)) return;
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final previousStatus = _event?.status;
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final shouldReplace =
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(previousStatus == FaceRecognitionSessionStatus.cold ||
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previousStatus == FaceRecognitionSessionStatus.failed) &&
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(event.status == FaceRecognitionSessionStatus.initializing ||
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event.status == FaceRecognitionSessionStatus.detecting);
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setState(() {
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_event = event;
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_previewError = null;
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});
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if (shouldReplace) unawaited(_initializeTexture(replace: true));
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}
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/// 按原生单调序号拒绝乱序快照，避免跨会话的旧空框覆盖较新的多人检测结果。
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bool _shouldAcceptEvent(FaceRecognitionSessionEvent event) {
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final current = _event;
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if (current == null) return true;
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if (current.eventSequence > 0 && event.eventSequence > 0) {
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if (event.eventSequence != current.eventSequence) {
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return event.eventSequence > current.eventSequence;
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}
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// MethodChannel 快照不含框；允许相同序号的真实 EventChannel 事件补齐它。
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return current.faceBoxes.isEmpty && event.faceBoxes.isNotEmpty;
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}
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if (event.sessionId != current.sessionId) {
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// 兼容旧版原生事件：活动识别期间不得让迟到的空闲资源快照清掉当前人脸框。
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return !(current.isActive && event.sessionId.isEmpty);
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}
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return event.revision >= current.revision;
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}
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/// 将原生事件通道异常收敛为预览内提示，不中断主屏查询状态机。
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void _handleEventError(Object error) {
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if (mounted) setState(() => _previewError = '摄像头状态连接异常，请检查设备');
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}
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/// 创建或替换预览 Texture，并释放异步迟到或已被替换的输出。
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Future<void> _initializeTexture({bool replace = false}) async {
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final requestId = ++_textureRequestId;
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if (replace) {
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final previous = _texture;
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_texture = null;
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if (previous != null) {
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try {
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await FaceDiscernPlugs.releasePreviewTexture(previous.textureId);
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} catch (_) {
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// 原生 Renderer 已冷释放时旧端点可能失效，仍要继续创建新 Texture 恢复画面。
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}
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}
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if (mounted) setState(() {});
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}
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try {
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final texture = await FaceDiscernPlugs.createPreviewTexture();
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if (!mounted || requestId != _textureRequestId) {
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await FaceDiscernPlugs.releasePreviewTexture(texture.textureId);
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return;
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}
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setState(() {
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_texture = texture;
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_previewError = null;
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});
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} catch (_) {
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// 已被新一轮 Texture 请求替代的旧异常不得覆盖新画面。
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if (mounted && requestId == _textureRequestId) {
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setState(() => _previewError = '摄像头画面暂不可用，请检查设备');
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}
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}
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}
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/// 取消事件订阅并释放当前 Engine 的 Texture，不触碰业务识别 Session。
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@override
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void dispose() {
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_textureRequestId++;
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unawaited(_eventSubscription?.cancel());
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final texture = _texture;
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_texture = null;
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if (texture != null) {
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unawaited(FaceDiscernPlugs.releasePreviewTexture(texture.textureId));
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}
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super.dispose();
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}
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/// 构建不会因 Session 暂停或结果展示而移除的实时画面。
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@override
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Widget build(BuildContext context) {
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final status = _previewError == null
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? _event?.status ?? FaceRecognitionSessionStatus.initializing
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: FaceRecognitionSessionStatus.failed;
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return Stack(
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fit: StackFit.expand,
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children: [
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FaceCameraPreview(
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texture: _texture,
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event: _event,
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status: status,
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statusText: widget.statusText,
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statusColor: widget.statusColor,
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scale: widget.scale,
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),
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if (_previewError != null)
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Center(
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child: Text(
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_previewError!,
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textAlign: TextAlign.center,
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style: TextStyle(
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color: Colors.white,
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fontSize: 16 * widget.scale,
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fontWeight: FontWeight.w700,
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),
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),
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),
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],
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);
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}
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}
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