1.创建发布者目录文件

cd d2lros2/
mkdir -p chapt3/chapt3_ws/src
cd chapt3/chapt3_ws/src

2.创建发布者节点
ros2 pkg create example_topic_rclcpp --build-type ament_cmake --dependencies rclcpp

3.新建发布者类
touch example_topic_rclcpp/src/topic_publisher_01.cpp

代码:

#include <chrono>
#include <functional>
#include <memory>
#include <string>

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

using namespace std::chrono_literals;

/* This example creates a subclass of Node and uses std::bind() to register a
* member function as a callback from the timer. */

class TopicPublisher01 : public rclcpp::Node
{
  public:
    TopicPublisher01()
    : Node("topic_publisher_01"), count_(0)
    {
      publisher_ = this->create_publisher<std_msgs::msg::String>("topic", 10);
      timer_ = this->create_wall_timer(
      500ms, std::bind(&TopicPublisher01::timer_callback, this));
    }

  private:
    void timer_callback()
    {
      auto message = std_msgs::msg::String();
      message.data = "Hello, world! " + std::to_string(count_++);
      RCLCPP_INFO(this->get_logger(), "Publishing: '%s'", message.data.c_str());
      publisher_->publish(message);
    }
    rclcpp::TimerBase::SharedPtr timer_;
    rclcpp::Publisher<std_msgs::msg::String>::SharedPtr publisher_;
    size_t count_;
};

int main(int argc, char * argv[])
{
  rclcpp::init(argc, argv);
  rclcpp::spin(std::make_shared<TopicPublisher01>());
  rclcpp::shutdown();
  return 0;
}
 

4.修改CMakeLists.txt

cmake_minimum_required(VERSION 3.8)
project(example_topic_rclcpp)

if(CMAKE_COMPILER_IS_GNUCXX OR CMAKE_CXX_COMPILER_ID MATCHES "Clang")
  add_compile_options(-Wall -Wextra -Wpedantic)
endif()

# find dependencies
find_package(ament_cmake REQUIRED)
find_package(rclcpp REQUIRED)
find_package(std_msgs REQUIRED)

if(BUILD_TESTING)
  find_package(ament_lint_auto REQUIRED)
  # the following line skips the linter which checks for copyrights
  # comment the line when a copyright and license is added to all source files
  set(ament_cmake_copyright_FOUND TRUE)
  # the following line skips cpplint (only works in a git repo)
  # comment the line when this package is in a git repo and when
  # a copyright and license is added to all source files
  set(ament_cmake_cpplint_FOUND TRUE)
  ament_lint_auto_find_test_dependencies()
endif()

ament_package()

add_executable(topic_publisher_01 src/topic_publisher_01.cpp)
ament_target_dependencies(topic_publisher_01 rclcpp std_msgs)

install(TARGETS
  topic_publisher_01
  DESTINATION lib/${PROJECT_NAME}
)

add_executable(topic_publisher_02 src/topic_publisher_02.cpp)

ament_target_dependencies(topic_publisher_02 rclcpp)

install(TARGETS
  topic_publisher_02
  DESTINATION lib/${PROJECT_NAME}
)

5.编译运行节点

cd chapt3/chapt3_ws/
colcon build --packages-select example_topic_rclcpp
source install/setup.bash
ros2 run example_topic_rclcpp topic_publisher_01
 

2.创建订阅者节点

tourch src/topic_subscribe_01.cpp

#include <memory>  
#include "rclcpp/rclcpp.hpp"   
#include "std_msgs/msg/string.hpp"   
using std::placeholders::_1;   
class TopicSubscribe01 : public rclcpp::Node   
{
  public:    
    TopicSubscribe01()    
    : Node("minimal_subscriber")    
    {
      subscription_ = this->create_subscription<std_msgs::msg::String>(
      "topic", 10, std::bind(&TopicSubscribe01::topic_callback, this, _1));
    }
  private:    
    void topic_callback(const std_msgs::msg::String & msg) const
    {
      RCLCPP_INFO(this->get_logger(), "I heard: '%s'", msg.data.c_str());
    }
    rclcpp::Subscription<std_msgs::msg::String>::SharedPtr subscription_;
};

int main(int argc, char * argv[])    
{
  rclcpp::init(argc, argv);    
  rclcpp::spin(std::make_shared<TopicSubscribe01>());
  rclcpp::shutdown();    
  return 0;    
}

3.修改CMakeLists.txt

cmake_minimum_required(VERSION 3.8)
project(example_topic_rclcpp)

if(CMAKE_COMPILER_IS_GNUCXX OR CMAKE_CXX_COMPILER_ID MATCHES "Clang")
  add_compile_options(-Wall -Wextra -Wpedantic)
endif()

# find dependencies
find_package(ament_cmake REQUIRED)
find_package(rclcpp REQUIRED)
find_package(std_msgs REQUIRED)

if(BUILD_TESTING)
  find_package(ament_lint_auto REQUIRED)
  # the following line skips the linter which checks for copyrights
  # comment the line when a copyright and license is added to all source files
  set(ament_cmake_copyright_FOUND TRUE)
  # the following line skips cpplint (only works in a git repo)
  # comment the line when this package is in a git repo and when
  # a copyright and license is added to all source files
  set(ament_cmake_cpplint_FOUND TRUE)
  ament_lint_auto_find_test_dependencies()
endif()

ament_package()

add_executable(topic_publisher_01 src/topic_publisher_01.cpp)
ament_target_dependencies(topic_publisher_01 rclcpp std_msgs)

add_executable(topic_publisher_02 src/topic_publisher_02.cpp)
ament_target_dependencies(topic_publisher_02 rclcpp)

add_executable(topic_subscribe_01 src/topic_subscribe_01.cpp)
ament_target_dependencies(topic_subscribe_01 rclcpp std_msgs)

install(TARGETS
  topic_publisher_01
  topic_publisher_02
  topic_subscribe_01
  DESTINATION lib/${PROJECT_NAME}
)
 

修改package.xml

<?xml version="1.0"?>
<?xml-model href="http://download.ros.org/schema/package_format3.xsd" schematypens="http://www.w3.org/2001/XMLSchema"?>
<package format="3">
  <name>example_topic_rclcpp</name>
  <version>0.0.0</version>
  <description>TODO: Package description</description>
  <maintainer email="joe@todo.todo">joe</maintainer>
  <license>TODO: License declaration</license>

  <buildtool_depend>ament_cmake</buildtool_depend>

  <depend>rclcpp</depend>
  <depend>std_msgs</depend>

  <test_depend>ament_lint_auto</test_depend>
  <test_depend>ament_lint_common</test_depend>

  <export>
    <build_type>ament_cmake</build_type>
  </export>
</package>
 

4.编译、运行节点

colcon build --packages-select example_topic_rclcpp
source install/setup.bash