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ROS2与C++入门教程-话题组件演示

ROS2与C++入门教程-话题组件演示

说明：

  • 介绍如何实现话题组件，利用组件发布话题和订阅话题

步骤：

  • 新建一个包cpp_component_topic
cd ~/dev_ws/src
ros2 pkg create --build-type ament_cmake cpp_component_topic
  • 进入include目录，新建文件talker_component.hpp
cd ~/dev_ws/src/cpp_component_topic/include/cpp_component_topic
touch talker_component.hpp
  • 内容如下：
#ifndef COMPOSITION__TALKER_COMPONENT_HPP_
#define COMPOSITION__TALKER_COMPONENT_HPP_

#include "cpp_component_topic/visibility_control.h"
#include "rclcpp/rclcpp.hpp"
#include "std_msgs/msg/string.hpp"

namespace composition
{

class Talker : public rclcpp::Node
{
public:
  COMPOSITION_PUBLIC
  explicit Talker(const rclcpp::NodeOptions & options);

protected:
  void on_timer();

private:
  size_t count_;
  rclcpp::Publisher<std_msgs::msg::String>::SharedPtr pub_;
  rclcpp::TimerBase::SharedPtr timer_;
};

}  // namespace composition

#endif  // COMPOSITION__TALKER_COMPONENT_HPP_
  • 进入include目录，新建文件listener_component.hpp
cd ~/dev_ws/src/cpp_component_topic/include/cpp_component_topic
touch listener_component.hpp
  • 内容如下：
#ifndef COMPOSITION__LISTENER_COMPONENT_HPP_
#define COMPOSITION__LISTENER_COMPONENT_HPP_

#include "cpp_component_topic/visibility_control.h"
#include "rclcpp/rclcpp.hpp"
#include "std_msgs/msg/string.hpp"

namespace composition
{

class Listener : public rclcpp::Node
{
public:
  COMPOSITION_PUBLIC
  explicit Listener(const rclcpp::NodeOptions & options);

private:
  rclcpp::Subscription<std_msgs::msg::String>::SharedPtr sub_;
};

}  // namespace composition

#endif  // COMPOSITION__LISTENER_COMPONENT_HPP_
  • 进入include目录，新建文件visibility_control.h
cd ~/dev_ws/src/cpp_component_topic/include/cpp_component_topic
touch visibility_control.h
  • 内容如下：
#ifndef COMPOSITION__VISIBILITY_CONTROL_H_
#define COMPOSITION__VISIBILITY_CONTROL_H_

#ifdef __cplusplus
extern "C"
{
#endif

// This logic was borrowed (then namespaced) from the examples on the gcc wiki:
//     https://gcc.gnu.org/wiki/Visibility

#if defined _WIN32 || defined __CYGWIN__
  #ifdef __GNUC__
    #define COMPOSITION_EXPORT __attribute__ ((dllexport))
    #define COMPOSITION_IMPORT __attribute__ ((dllimport))
  #else
    #define COMPOSITION_EXPORT __declspec(dllexport)
    #define COMPOSITION_IMPORT __declspec(dllimport)
  #endif
  #ifdef COMPOSITION_BUILDING_DLL
    #define COMPOSITION_PUBLIC COMPOSITION_EXPORT
  #else
    #define COMPOSITION_PUBLIC COMPOSITION_IMPORT
  #endif
  #define COMPOSITION_PUBLIC_TYPE COMPOSITION_PUBLIC
  #define COMPOSITION_LOCAL
#else
  #define COMPOSITION_EXPORT __attribute__ ((visibility("default")))
  #define COMPOSITION_IMPORT
  #if __GNUC__ >= 4
    #define COMPOSITION_PUBLIC __attribute__ ((visibility("default")))
    #define COMPOSITION_LOCAL  __attribute__ ((visibility("hidden")))
  #else
    #define COMPOSITION_PUBLIC
    #define COMPOSITION_LOCAL
  #endif
  #define COMPOSITION_PUBLIC_TYPE
#endif

#ifdef __cplusplus
}
#endif

#endif  // COMPOSITION__VISIBILITY_CONTROL_H_
  • 进入src目录，新建文件talker_component.cpp
cd ~/dev_ws/src/cpp_component_topic/src
touch talker_component.cpp
  • 内容如下：
#include "cpp_component_topic/talker_component.hpp"

#include <chrono>
#include <iostream>
#include <memory>
#include <utility>

#include "rclcpp/rclcpp.hpp"
#include "std_msgs/msg/string.hpp"

using namespace std::chrono_literals;

namespace composition
{

// Create a Talker "component" that subclasses the generic rclcpp::Node base class.
// Components get built into shared libraries and as such do not write their own main functions.
// The process using the component's shared library will instantiate the class as a ROS node.
Talker::Talker(const rclcpp::NodeOptions & options)
: Node("talker", options), count_(0)
{
  // Create a publisher of "std_mgs/String" messages on the "chatter" topic.
  pub_ = create_publisher<std_msgs::msg::String>("chatter", 10);

  // Use a timer to schedule periodic message publishing.
  timer_ = create_wall_timer(1s, std::bind(&Talker::on_timer, this));
}

void Talker::on_timer()
{
  auto msg = std::make_unique<std_msgs::msg::String>();
  msg->data = "Hello World: " + std::to_string(++count_);
  RCLCPP_INFO(this->get_logger(), "Publishing: '%s'", msg->data.c_str());
  std::flush(std::cout);

  // Put the message into a queue to be processed by the middleware.
  // This call is non-blocking.
  pub_->publish(std::move(msg));
}

}  // namespace composition

#include "rclcpp_components/register_node_macro.hpp"

// Register the component with class_loader.
// This acts as a sort of entry point, allowing the component to be discoverable when its library
// is being loaded into a running process.
RCLCPP_COMPONENTS_REGISTER_NODE(composition::Talker)
  • 进入src目录，新建文件listener_component.cpp
cd ~/dev_ws/src/cpp_component_topic/src
touch listener_component.cpp
  • 内容如下：
#include "cpp_component_topic/listener_component.hpp"

#include <iostream>
#include <memory>

#include "rclcpp/rclcpp.hpp"
#include "std_msgs/msg/string.hpp"

namespace composition
{

// Create a Listener "component" that subclasses the generic rclcpp::Node base class.
// Components get built into shared libraries and as such do not write their own main functions.
// The process using the component's shared library will instantiate the class as a ROS node.
Listener::Listener(const rclcpp::NodeOptions & options)
: Node("listener", options)
{
  // Create a callback function for when messages are received.
  // Variations of this function also exist using, for example, UniquePtr for zero-copy transport.
  auto callback =
    [this](std_msgs::msg::String::ConstSharedPtr msg) -> void
    {
      RCLCPP_INFO(this->get_logger(), "I heard: [%s]", msg->data.c_str());
      std::flush(std::cout);
    };

  // Create a subscription to the "chatter" topic which can be matched with one or more
  // compatible ROS publishers.
  // Note that not all publishers on the same topic with the same type will be compatible:
  // they must have compatible Quality of Service policies.
  sub_ = create_subscription<std_msgs::msg::String>("chatter", 10, callback);
}

}  // namespace composition

#include "rclcpp_components/register_node_macro.hpp"

// Register the component with class_loader.
// This acts as a sort of entry point, allowing the component to be discoverable when its library
// is being loaded into a running process.
RCLCPP_COMPONENTS_REGISTER_NODE(composition::Listener)
  • 编译package.xml
  • 在<buildtool_depend>ament_cmake</buildtool_depend>后增加
  <depend>rclcpp</depend>
  <depend>rclcpp_components</depend>
  <depend>std_msgs</depend>
  • 编译CMakelist.txt
  • 在find_package(ament_cmake REQUIRED)后增加
find_package(rclcpp REQUIRED)
find_package(rclcpp_components REQUIRED)
find_package(std_msgs REQUIRED)
  • 编译为共享库并注册talker_component和listener_component 组件
include_directories(include)
# create ament index resource which references the libraries in the binary dir
set(node_plugins "")

add_library(talker_component SHARED
  src/talker_component.cpp)
target_compile_definitions(talker_component
  PRIVATE "COMPOSITION_BUILDING_DLL")
ament_target_dependencies(talker_component
  "rclcpp"
  "rclcpp_components"
  "std_msgs")
rclcpp_components_register_nodes(talker_component "composition::Talker")
set(node_plugins "${node_plugins}composition::Talker;$<TARGET_FILE:talker_component>\n")

add_library(listener_component SHARED
  src/listener_component.cpp)
target_compile_definitions(listener_component
  PRIVATE "COMPOSITION_BUILDING_DLL")
ament_target_dependencies(listener_component
  "rclcpp"
  "rclcpp_components"
  "std_msgs")
rclcpp_components_register_nodes(listener_component "composition::Listener")
set(node_plugins "${node_plugins}composition::Listener;$<TARGET_FILE:listener_component>\n")
  • 生成和安装相关库文件和执行文件
install(TARGETS
  talker_component
  listener_component
  ARCHIVE DESTINATION lib
  LIBRARY DESTINATION lib
  RUNTIME DESTINATION bin)
  • 安装相关依赖
cd ~/dev_ws/
rosdep install -i --from-path src --rosdistro galactic -y
  • 编译包
colcon build --symlink-install --packages-select cpp_component_topic
  • 加载工作空间
. install/setup.bash
  • 查看工作区中已注册和可用的组件，
  • 执行以下命令：
 ros2 component types
  • 效果如下：
$ ros2 component types
cpp_component_topic
  composition::Talker
  composition::Listener
  • 启动组件容器
ros2 run rclcpp_components component_container
  • 查看组件容器名称
$ ros2 component list
/ComponentManager
  • 加载话题发布组件到容器/ComponentManager
ros2 component load /ComponentManager cpp_component_topic composition::Talker
  • 加载话题订阅组件到容器/ComponentManager
ros2 component load /ComponentManager cpp_component_topic composition::Listener
  • 在运行启动容器组件的终端下显示
  • 效果如下:
$ ros2 run rclcpp_components component_container
[INFO] [1651828582.770254908] [ComponentManager]: Load Library: /home/ubuntu/dev_ws/install/cpp_component_topic/lib/libtalker_component.so
[INFO] [1651828582.771588494] [ComponentManager]: Found class: rclcpp_components::NodeFactoryTemplate<composition::Talker>
[INFO] [1651828582.771636618] [ComponentManager]: Instantiate class: rclcpp_components::NodeFactoryTemplate<composition::Talker>
[INFO] [1651828583.778235165] [talker]: Publishing: 'Hello World: 1'
[INFO] [1651828584.778106888] [talker]: Publishing: 'Hello World: 2'
[INFO] [1651828585.778120521] [talker]: Publishing: 'Hello World: 3'
[INFO] [1651828586.778131945] [talker]: Publishing: 'Hello World: 4'
[INFO] [1651828587.778147302] [talker]: Publishing: 'Hello World: 5'
[INFO] [1651828588.778142863] [talker]: Publishing: 'Hello World: 6'
[INFO] [1651828589.778147971] [talker]: Publishing: 'Hello World: 7'
[INFO] [1651828590.778161248] [talker]: Publishing: 'Hello World: 8'
[INFO] [1651828591.778150505] [talker]: Publishing: 'Hello World: 9'
[INFO] [1651828592.778146954] [talker]: Publishing: 'Hello World: 10'
[INFO] [1651828593.778187735] [talker]: Publishing: 'Hello World: 11'
[INFO] [1651828594.778167919] [talker]: Publishing: 'Hello World: 12'
[INFO] [1651828595.778172696] [talker]: Publishing: 'Hello World: 13'
[INFO] [1651828596.778191892] [talker]: Publishing: 'Hello World: 14'
[INFO] [1651828597.778179234] [talker]: Publishing: 'Hello World: 15'
[INFO] [1651828598.778193295] [talker]: Publishing: 'Hello World: 16'
[INFO] [1651828599.778488985] [talker]: Publishing: 'Hello World: 17'
[INFO] [1651828600.778116399] [talker]: Publishing: 'Hello World: 18'
[INFO] [1651828601.778118538] [talker]: Publishing: 'Hello World: 19'
[INFO] [1651828602.778213187] [talker]: Publishing: 'Hello World: 20'
[INFO] [1651828602.917031454] [ComponentManager]: Load Library: /home/ubuntu/dev_ws/install/cpp_component_topic/lib/liblistener_component.so
[INFO] [1651828602.920950689] [ComponentManager]: Found class: rclcpp_components::NodeFactoryTemplate<composition::Listener>
[INFO] [1651828602.921096170] [ComponentManager]: Instantiate class: rclcpp_components::NodeFactoryTemplate<composition::Listener>
[INFO] [1651828603.778212564] [talker]: Publishing: 'Hello World: 21'
[INFO] [1651828603.778760322] [listener]: I heard: [Hello World: 21]
[INFO] [1651828604.778251609] [talker]: Publishing: 'Hello World: 22'
[INFO] [1651828604.778627732] [listener]: I heard: [Hello World: 22]
[INFO] [1651828605.778229471] [talker]: Publishing: 'Hello World: 23'
[INFO] [1651828605.778546161] [listener]: I heard: [Hello World: 23]
[INFO] [1651828606.778232862] [talker]: Publishing: 'Hello World: 24'
[INFO] [1651828606.778629619] [listener]: I heard: [Hello World: 24]
[INFO] [1651828607.778242430] [talker]: Publishing: 'Hello World: 25'
[INFO] [1651828607.778584759] [listener]: I heard: [Hello World: 25]
[INFO] [1651828608.778185347] [talker]: Publishing: 'Hello World: 26'
[INFO] [1651828608.778519307] [listener]: I heard: [Hello World: 26]
[INFO] [1651828609.778234386] [talker]: Publishing: 'Hello World: 27'
[INFO] [1651828609.778680409] [listener]: I heard: [Hello World: 27]
[INFO] [1651828610.778255996] [talker]: Publishing: 'Hello World: 28'
[INFO] [1651828610.778559937] [listener]: I heard: [Hello World: 28]

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