添加取消订阅的逻辑

include/mqtt_client.hpp

@@ -1,12 +1,14 @@
 // mqtt_client.hpp
 #pragma once
 
-#include <string>
+#include <mqtt/async_client.h>
+
+#include <atomic>
 #include <functional>
 #include <memory>
-#include <atomic>
 #include <mutex>
-#include <mqtt/async_client.h>
+#include <string>
+
 #include "app_config.hpp"
 #include "logger.hpp"
 
@@ -29,6 +31,7 @@ public:
     void force_disconnect();
     void publish(const std::string& topic, const std::string& payload, int qos = -1);
     void subscribe(const std::string& topic, int qos = -1);
+    void unsubscribe(const std::string& topic);
     void switchServer(const MQTTConfig& newConfig);
 
     bool isConnected() const;

src/mqtt_client.cpp

@@ -137,6 +137,21 @@ void MQTTClient::subscribe(const std::string& topic, int qos)
     }
 }
 
+void MQTTClient::unsubscribe(const std::string& topic)
+{
+    if (!connected_ || topic.empty()) return;
+
+    try
+    {
+        client_->unsubscribe(topic);
+        LOG_INFO("[MQTT] Unsubscribed from topic: " + topic);
+    }
+    catch (const mqtt::exception& e)
+    {
+        LOG_WARN(std::string("[MQTT] Unsubscribe failed: ") + e.what());
+    }
+}
+
 void MQTTClient::switchServer(const MQTTConfig& newConfig)
 {
     std::lock_guard<std::mutex> lock(mutex_);

src/mqtt_client_wrapper.cpp

@@ -25,15 +25,31 @@ static std::string g_last_vid;
 static bool try_activate_mqtt()
 {
     if (g_app_config.runtime_vid.empty()) return false;
+    if (!mqtt_client || !mqtt_client->isConnected()) return false;
 
+    // 如果已激活且 VID 未变化，什么都不做
     if (g_mqtt_activated.load() && g_last_vid == g_app_config.runtime_vid) return true;
 
-    // VID 首次 or 发生变化
+    // ---------- 1. 如果是 VID 变化，先取消旧订阅 ----------
+    if (g_mqtt_activated.load())
+    {
+        LOG_INFO("[MQTT] VID changed, unsubscribe old topics: " + g_last_vid);
+
+        mqtt_client->unsubscribe(g_prev_topics.video_down);
+        mqtt_client->unsubscribe(g_prev_topics.record_query);
+        mqtt_client->unsubscribe(g_prev_topics.record_play);
+        mqtt_client->unsubscribe(g_prev_topics.vehicle_ctrl);
+        mqtt_client->unsubscribe(g_prev_topics.heartbeat_up);
+    }
+
+    // ---------- 2. 切换到新 VID ----------
     g_app_config.mqtt.topics.fill_with_veh_id(g_app_config.runtime_vid);
+    g_prev_topics = g_app_config.mqtt.topics;
     g_last_vid = g_app_config.runtime_vid;
 
     LOG_INFO("[MQTT] Activated with VID=" + g_last_vid);
 
+    // ---------- 3. 订阅新 topic ----------
     mqtt_client->subscribe(g_app_config.mqtt.topics.video_down);
     mqtt_client->subscribe(g_app_config.mqtt.topics.record_query);
     mqtt_client->subscribe(g_app_config.mqtt.topics.record_play);