refactor(android): 重构Android端实现使用官方SDK替代反射调用

- 移除反射机制，直接集成CH934XLib.jar官方SDK
- 添加CH934XManager初始化逻辑并处理Application上下文兼容性
- 实现设备枚举、串口打开关闭等核心功能的直接调用
- 集成IDataCallback和IModemStatus回调处理
- 更新异常回调机制，支持原生层主动推送异常事件
- 优化设备连接状态管理和USB权限处理
- 为Dart模型类添加相等性比较和哈希码实现
- 更新示例应用UI以适配新的串口索引选择逻辑

example/lib/main.dart

@@ -43,7 +43,9 @@ class _Ch934xSerialExamplePageState extends State<Ch934xSerialExamplePage> {
 
   List<Ch934xDeviceInfo> _devices = const <Ch934xDeviceInfo>[];
   Ch934xDeviceInfo? _selectedDevice;
-  Ch934xSerialPortInfo? _selectedPort;
+  /// 当前选中设备的可用串口索引集合(由 SDK getSerialCount 决定)。
+  List<int> _availablePortIndices = const <int>[];
+  int? _selectedPortIndex;
   StreamSubscription<Ch934xException>? _exceptionSubscription;
   StreamSubscription<Uint8List>? _dataSubscription;
 
@@ -87,26 +89,58 @@ class _Ch934xSerialExamplePageState extends State<Ch934xSerialExamplePage> {
   Future<void> _refreshDeviceList() async {
     try {
       final devices = await _plugin.getDeviceList();
+      if (!mounted) return;
       setState(() {
         _devices = devices;
+        // 清理已不再列表中的旧选项,避免 DropdownButton value 不在 items 中报错。
+        final selected = _selectedDevice;
+        if (selected != null && !devices.contains(selected)) {
+          _selectedDevice = null;
+          _availablePortIndices = const <int>[];
+          _selectedPortIndex = null;
+        } else if (selected != null) {
+          _availablePortIndices = _resolvePortIndices(selected);
+          final current = _selectedPortIndex;
+          if (current == null || !_availablePortIndices.contains(current)) {
+            _selectedPortIndex = _availablePortIndices.isNotEmpty
+                ? _availablePortIndices.first
+                : null;
+          }
+        }
         _status = '已扫描到 ${devices.length} 台 CH934X 设备';
       });
     } on Exception catch (e) {
+      if (!mounted) return;
       setState(() => _status = '设备扫描失败: $e');
     }
   }
 
+  /// 把设备的串口描述转换为可用索引列表。
+  ///
+  /// 优先使用 SDK 返回的 [Ch934xSerialPortInfo.portIndex],缺
+  /// 失时回退到 0..N-1,确保 UI 始终有可选项。
+  List<int> _resolvePortIndices(Ch934xDeviceInfo device) {
+    if (device.serialPorts.isNotEmpty) {
+      return device.serialPorts.map((p) => p.portIndex).toList()..sort();
+    }
+    if (device.interfaceCount > 0) {
+      return List<int>.generate(device.interfaceCount, (i) => i);
+    }
+    // 最坏情况下,允许打开串口 0;用户可通过业务调用切换。
+    return const <int>[0];
+  }
+
   Future<void> _openPort() async {
     final device = _selectedDevice;
-    final port = _selectedPort;
-    if (device == null || port == null) {
+    final portIndex = _selectedPortIndex;
+    if (device == null || portIndex == null) {
       setState(() => _status = '请先选择设备与串口');
       return;
     }
     final target = Ch934xPortTarget(
       deviceId: device.deviceId,
-      interfaceNumber: device.interfaceCount > 0 ? 0 : 0,
-      serialPortIndex: port.portIndex,
+      interfaceNumber: 0,
+      serialPortIndex: portIndex,
     );
     final ok = await _plugin.openPort(target);
     if (!ok) {
@@ -115,7 +149,7 @@ class _Ch934xSerialExamplePageState extends State<Ch934xSerialExamplePage> {
     }
     setState(() {
       _portOpened = true;
-      _status = '串口 ${port.portIndex} 已打开';
+      _status = '串口 $portIndex 已打开';
     });
     _startReceiving();
   }
@@ -215,27 +249,33 @@ class _Ch934xSerialExamplePageState extends State<Ch934xSerialExamplePage> {
                 onChanged: (device) {
                   setState(() {
                     _selectedDevice = device;
-                    _selectedPort = device?.serialPorts.isNotEmpty == true
-                        ? device!.serialPorts.first
-                        : null;
+                    if (device == null) {
+                      _availablePortIndices = const <int>[];
+                      _selectedPortIndex = null;
+                    } else {
+                      _availablePortIndices = _resolvePortIndices(device);
+                      _selectedPortIndex = _availablePortIndices.isNotEmpty
+                          ? _availablePortIndices.first
+                          : null;
+                    }
                   });
                 },
               ),
-            if (_selectedDevice?.serialPorts.isNotEmpty == true) ...[
+            if (_selectedDevice != null) ...[
               const SizedBox(height: 8),
-              DropdownButton<Ch934xSerialPortInfo>(
+              DropdownButton<int>(
                 isExpanded: true,
-                value: _selectedPort,
+                value: _selectedPortIndex,
                 hint: const Text('选择串口'),
-                items: _selectedDevice!.serialPorts
+                items: _availablePortIndices
                     .map(
-                      (p) => DropdownMenuItem<Ch934xSerialPortInfo>(
-                        value: p,
-                        child: Text('port #${p.portIndex}'),
+                      (idx) => DropdownMenuItem<int>(
+                        value: idx,
+                        child: Text('port #$idx'),
                       ),
                     )
                     .toList(),
-                onChanged: (p) => setState(() => _selectedPort = p),
+                onChanged: (idx) => setState(() => _selectedPortIndex = idx),
               ),
             ],
             const SizedBox(height: 16),