fix(MqttManager): 防止MQTT客户端重复连接

添加 `isConnecting` 标志位以跟踪连接状态，避免在连接过程中发起新的连接请求。
在连接失败时安全重置客户端，并在连接完成或丢失时正确更新状态标志。

app/src/main/java/com/example/lzwcai_terminal_temi/MqttManager.kt

@@ -36,6 +36,8 @@ class MqttManager(
     private val job = SupervisorJob()
     private val scope = CoroutineScope(Dispatchers.IO + job)
     private var reconnectJob: Job? = null
+    @Volatile
+    private var isConnecting: Boolean = false
     private val prefs = appContext.getSharedPreferences("app_prefs", Context.MODE_PRIVATE)
     private val agentDempIdKey = "agent_demp_id"
 
@@ -57,10 +59,15 @@ class MqttManager(
     private var danceJob: Job? = null
 
     init {
+        createMqttClient()
+    }
+
+    private fun createMqttClient() {
         try {
             mqttClient = MqttClient(brokerUri, clientId, MemoryPersistence())
             mqttClient?.setCallback(object : MqttCallbackExtended {
                 override fun connectComplete(reconnect: Boolean, serverURI: String?) {
+                    isConnecting = false
                     Log.i(TAG, "MQTT connection complete. Reconnect: $reconnect")
                     subscribeTopic("robot/cmd")
                     subscribeTopic("soul2user")
@@ -68,6 +75,7 @@ class MqttManager(
                 }
 
                 override fun connectionLost(cause: Throwable?) {
+                    isConnecting = false
                     Log.e(TAG, "Connection lost: ${cause?.message}")
                     updateConnectionStatus(false)
                     scheduleReconnect()
@@ -96,6 +104,10 @@ class MqttManager(
                 updateConnectionStatus(true)
                 return@launch
             }
+            if (isConnecting) {
+                Log.d(TAG, "MQTT connect skipped: already connecting.")
+                return@launch
+            }
             val username = prefs.getString(HttpManager.PREF_KEY_MQTT_USERNAME, "").orEmpty().trim()
             val password = prefs.getString(HttpManager.PREF_KEY_MQTT_PASSWORD, "").orEmpty()
             if (username.isEmpty() || password.isEmpty()) {
@@ -103,8 +115,12 @@ class MqttManager(
                 updateConnectionStatus(false)
                 return@launch
             }
+            if (mqttClient == null) {
+                createMqttClient()
+            }
             Log.i(TAG, "Attempting to connect to MQTT broker at $brokerUri")
             try {
+                isConnecting = true
                 val options = MqttConnectOptions().apply {
                     isAutomaticReconnect = false
                     isCleanSession = true
@@ -114,8 +130,10 @@ class MqttManager(
                     this.password = password.toCharArray()
                 }
                 mqttClient?.connect(options)
-            } catch (e: MqttException) {
-                Log.e(TAG, "Initial connection failed: ${e.message}")
+            } catch (t: Throwable) {
+                Log.e(TAG, "Initial connection failed", t)
+                isConnecting = false
+                resetClientSafely()
                 updateConnectionStatus(false)
                 scheduleReconnect()
             }
@@ -137,6 +155,7 @@ class MqttManager(
         scope.launch {
             try {
                 reconnectJob?.cancel() 
+                isConnecting = false
                 if (mqttClient?.isConnected == true) {
                     mqttClient?.disconnect()
                     Log.i(TAG, "Disconnected from MQTT broker.")
@@ -151,7 +170,7 @@ class MqttManager(
 
     fun shutdown() {
         reconnectJob?.cancel()
-        job.cancel()
+        isConnecting = false
         try {
             if (mqttClient?.isConnected == true) {
                 mqttClient?.disconnect()
@@ -165,6 +184,16 @@ class MqttManager(
         }
     }
 
+    private fun resetClientSafely() {
+        try {
+            mqttClient?.close()
+        } catch (_: Exception) {
+        } finally {
+            mqttClient = null
+        }
+        createMqttClient()
+    }
+
     private fun updateConnectionStatus(connected: Boolean) {
         Handler(Looper.getMainLooper()).post {
             statusListener(connected)