说明：
- 介绍如何创建消息msg文件
步骤：
- 使用已经建好的工作空间dev_ws
- 新建包
cd ~/dev-ws/src
ros2 pkg create --build-type ament_cmake tutorial_interfaces
- 新建目录mkdir msg
cd ~/dev-ws/src/tutorial_interfaces
mkdir msg
- 增加msg定义文件
cd ~/dev-ws/src/tutorial_interfaces/msg
vim Num.msg
- 内容如下：
int64 num
- 定义一个64位的整数
- 编辑CMakeLists.txt，增加如下行
find_package(rosidl_default_generators REQUIRED)
rosidl_generate_interfaces(${PROJECT_NAME}
"msg/Num.msg"
)
- 编辑package.xml，增加如下行
<build_depend>rosidl_default_generators</build_depend>
<exec_depend>rosidl_default_runtime</exec_depend>
<member_of_group>rosidl_interface_packages</member_of_group>
- 编译包
cd ~/dev_ws/
colcon build --symlink-install --packages-select tutorial_interfaces
- 接着重新加载工作空间
. install/setup.bash
- 查询消息接口
ros2 interface show tutorial_interfaces/msg/Num
- 效果如下：
int64 num
测试：
- 使用之前的cpp_pubsub包的发布
- 复制publisher_member_function.cpp到publisher_member_function_num.cpp
cd ~/dev_ws/src/cpp_pubsub/src
cp publisher_member_function.cpp publisher_member_function_num.cpp
- 修改为：
#include <chrono>
#include <memory>
#include "rclcpp/rclcpp.hpp"
#include "tutorial_interfaces/msg/num.hpp" // CHANGE
using namespace std::chrono_literals;
class MinimalPublisher : public rclcpp::Node
{
public:
MinimalPublisher()
: Node("minimal_publisher"), count_(0)
{
publisher_ = this->create_publisher<tutorial_interfaces::msg::Num>("topic", 10); // CHANGE
timer_ = this->create_wall_timer(
500ms, std::bind(&MinimalPublisher::timer_callback, this));
}
private:
void timer_callback()
{
auto message = tutorial_interfaces::msg::Num(); // CHANGE
message.num = this->count_++; // CHANGE
RCLCPP_INFO(this->get_logger(), "Publishing: '%d'", message.num); // CHANGE
publisher_->publish(message);
}
rclcpp::TimerBase::SharedPtr timer_;
rclcpp::Publisher<tutorial_interfaces::msg::Num>::SharedPtr publisher_; // CHANGE
size_t count_;
};
int main(int argc, char * argv[])
{
rclcpp::init(argc, argv);
rclcpp::spin(std::make_shared<MinimalPublisher>());
rclcpp::shutdown();
return 0;
}
- 使用之前的cpp_pubsub包的订阅
- 复制subscriber_member_function.cpp到subscriber_member_function_num.cpp
- 修改如下：
#include <memory>
#include "rclcpp/rclcpp.hpp"
#include "tutorial_interfaces/msg/num.hpp" // CHANGE
using std::placeholders::_1;
class MinimalSubscriber : public rclcpp::Node
{
public:
MinimalSubscriber()
: Node("minimal_subscriber")
{
subscription_ = this->create_subscription<tutorial_interfaces::msg::Num>( // CHANGE
"topic", 10, std::bind(&MinimalSubscriber::topic_callback, this, _1));
}
private:
void topic_callback(const tutorial_interfaces::msg::Num::SharedPtr msg) const // CHANGE
{
RCLCPP_INFO(this->get_logger(), "I heard: '%d'", msg->num); // CHANGE
}
rclcpp::Subscription<tutorial_interfaces::msg::Num>::SharedPtr subscription_; // CHANGE
};
int main(int argc, char * argv[])
{
rclcpp::init(argc, argv);
rclcpp::spin(std::make_shared<MinimalSubscriber>());
rclcpp::shutdown();
return 0;
}
- 修改CMakeLists.txt
...
find_package(ament_cmake REQUIRED)
find_package(rclcpp REQUIRED)
find_package(tutorial_interfaces REQUIRED) # CHANGE
add_executable(talker_num src/publisher_member_function_num.cpp) # CHANGE
ament_target_dependencies(talker_num rclcpp tutorial_interfaces) # CHANGE
add_executable(listener_num src/subscriber_member_function_num.cpp) # CHANGE
ament_target_dependencies(listener_num rclcpp tutorial_interfaces) # CHANGE
install(TARGETS
talker
listener
talker_num # CHANGE
listener_num # CHANGE
DESTINATION lib/${PROJECT_NAME})
ament_package()
- 修改package.xml，增加：
<depend>tutorial_interfaces</depend>
- 重新编译包
cd ~/dev_ws/
colcon build --packages-select cpp_pubsub
- 运行测试发布：
ros2 run cpp_pubsub talker_num
[INFO] [minimal_publisher]: Publishing: '0'
[INFO] [minimal_publisher]: Publishing: '1'
[INFO] [minimal_publisher]: Publishing: '2'
- 运行测试订阅
ros2 run cpp_pubsub listener_num
