Added simple API to listen for ros2 system component state change (o3de#599)

Signed-off-by: Mateusz Wasilewski <[email protected]>

Author: mateuszwasilewski

Gems/ROS2/Code/Include/ROS2/ROS2Bus.h

@@ -8,10 +8,11 @@
 #pragma once
 
 #include <AzCore/EBus/EBus.h>
+#include <AzCore/EBus/Event.h>
 #include <AzCore/Interface/Interface.h>
+#include <ROS2/Clock/SimulationClock.h>
 #include <builtin_interfaces/msg/time.hpp>
 #include <geometry_msgs/msg/transform_stamped.hpp>
-#include <ROS2/Clock/SimulationClock.h>
 #include <rclcpp/node.hpp>
 
 namespace ROS2
@@ -24,6 +25,8 @@ namespace ROS2
     class ROS2Requests
     {
     public:
+        using NodeChangedEvent = AZ::Event<std::shared_ptr<rclcpp::Node>>;
+
         AZ_RTTI(ROS2Requests, "{a9bdbff6-e644-430d-8096-cdb53c88e8fc}");
         virtual ~ROS2Requests() = default;
 
@@ -33,6 +36,12 @@ namespace ROS2
         //! @note Alternatively, you can use your own node along with an executor.
         virtual std::shared_ptr<rclcpp::Node> GetNode() const = 0;
 
+        //! Attach handler to ROS2 node change events.
+        //! You can use this method to correctly initialize SystemComponents that depend on ROS2Node.
+        //! @param handler which will be connected to NodeChangedEvent.
+        //! @note callback is active as long as handler is not destroyed.
+        virtual void ConnectOnNodeChanged(NodeChangedEvent::Handler& handler) = 0;
+
         //! Acquire current time as ROS2 timestamp.
         //! Timestamps provide temporal context for messages such as sensor data.
         //! @code
@@ -55,7 +64,6 @@ namespace ROS2
         //! Obtains a simulation clock that is used across simulation.
         //! @returns constant reference to currently running clock.
         virtual const SimulationClock& GetSimulationClock() const = 0;
-
     };
 
     class ROS2BusTraits : public AZ::EBusTraits

Gems/ROS2/Code/Source/ROS2SystemComponent.cpp

@@ -151,6 +151,7 @@ namespace ROS2
 
         ROS2RequestBus::Handler::BusConnect();
         AZ::TickBus::Handler::BusConnect();
+        m_nodeChangedEvent.Signal(m_ros2Node);
     }
 
     void ROS2SystemComponent::Deactivate()
@@ -165,6 +166,7 @@ namespace ROS2
         m_executor.reset();
         m_simulationClock.reset();
         m_ros2Node.reset();
+        m_nodeChangedEvent.Signal(m_ros2Node);
     }
 
     builtin_interfaces::msg::Time ROS2SystemComponent::GetROSTimestamp() const
@@ -177,6 +179,11 @@ namespace ROS2
         return m_ros2Node;
     }
 
+    void ROS2SystemComponent::ConnectOnNodeChanged(NodeChangedEvent::Handler& handler)
+    {
+        handler.Connect(m_nodeChangedEvent);
+    }
+
     const SimulationClock& ROS2SystemComponent::GetSimulationClock() const
     {
         return *m_simulationClock;

Gems/ROS2/Code/Source/ROS2SystemComponent.h

@@ -61,6 +61,7 @@ namespace ROS2
         //////////////////////////////////////////////////////////////////////////
         // ROS2RequestBus::Handler overrides
         std::shared_ptr<rclcpp::Node> GetNode() const override;
+        void ConnectOnNodeChanged(NodeChangedEvent::Handler& handler) override;
         builtin_interfaces::msg::Time GetROSTimestamp() const override;
         void BroadcastTransform(const geometry_msgs::msg::TransformStamped& t, bool isDynamic) override;
         const SimulationClock& GetSimulationClock() const override;
@@ -90,6 +91,7 @@ namespace ROS2
         AZStd::unique_ptr<tf2_ros::TransformBroadcaster> m_dynamicTFBroadcaster;
         AZStd::unique_ptr<tf2_ros::StaticTransformBroadcaster> m_staticTFBroadcaster;
         AZStd::unique_ptr<SimulationClock> m_simulationClock;
+        NodeChangedEvent m_nodeChangedEvent;
         //! Load the pass templates of the ROS2 gem.
         void LoadPassTemplateMappings();
         AZ::RPI::PassSystemInterface::OnReadyLoadTemplatesEvent::Handler m_loadTemplatesHandler;