ROS 5: 自定义消息话题

实现目标：完成宝可梦信息的话题传输

自定义话题的流程：

graph TB
a(定义msg文件)
a -->b(package.xml中添加依赖)
b -->c(CMakeLists.txt添加编译选项)
c -->d(编译生成相关文件)

一、定义消息

先定义消息类型，ros使用*.msg格式存储消息。

msg文件不是编程语言，所以在编译的时候，会根据不同的编程语言动态扩展层不同的数据类型。

string name		#名字
string type		#属性
uint8  gender	#性别

uint8 unknown = 0
uint8 male    = 1
uint8 female  = 2

二、修改package.xml

在功能包的package.xml里，增加两句话，为其增加依赖包。包名如下：

<build_depend>message_generation</build_depend>
<exec_depend>message_runtime</exec_depend>

三、调整CMakeLists.txt

在CMakeLists.txt中补充以下内容

1、在第十行find_package的最后补充上message_generation.

find_package(catkin REQUIRED COMPONENTS
  geometry_msgs
  roscpp
  rospy
  std_msgs
  turtlesim
  message_generation
)

2、声明ROS消息。在Declare ROS dynamic reconfigure parameters上方，有关于msg编译的指导。

## 在“msg”文件夹中生成消息
# add_message_files(
#   FILES
#   Message1.msg
#   Message2.msg
# )

## 在“srv”文件夹中生成服务
# add_service_files(
#   FILES
#   Service1.srv
#   Service2.srv
# )

## 在“action”文件夹中生成操作
# add_action_files(
#   FILES
#   Action1.action
#   Action2.action
# )

## 生成具有在此处列出的任何依赖项的添加消息和服务
# generate_messages(
#   DEPENDENCIES
#   geometry_msgs#   std_msgs
# )

我们只需写入：

add_message_files(
  FILES
  Pokemon.msg
)

generate_messages(
  DEPENDENCIES
  std_msgs
)

################################################
## Declare ROS dynamic reconfigure parameters ##
################################################

3、在catkin_package增加运行依赖

###################################
## catkin specific configuration ##
###################################

catkin_package(
  CATKIN_DEPENDS geometry_msgs roscpp rospy std_msgs turtlesim message_runtime
  )

完成上述修改后，在工作空间使用catkin_make编译，然后在工作空间的devel中就可以找到这个功能包的文件夹，里面就含有一个Pokemon.h头文件。

四，编写代码

c++

publisher

#include <ros/ros.h>
#include "learn_topic/Pokemon.h"

int main(int argc,char **argv){
    
    ros::init(argc,argv,"pokemon_pub_topic");
    ros::NodeHandle n;
    ros::Publisher Pub_Pokemon = n.advertise<learn_topic::Pokemon>("/pokemon_info",10);
    ros::Rate loop_rate(10);

    while (ros::ok())
    {
    	learn_topic::Pokemon pokemon_msg;
		pokemon_msg.name = "pikachu";
		pokemon_msg.type  = "electric";
		pokemon_msg.gender  = learn_topic::Pokemon::male;

		Pub_Pokemon.publish(pokemon_msg);
        ROS_INFO("Publish Pokemon INfo\n\t name:%s type:%s gender:%d",     pokemon_msg.name.c_str(),pokemon_msg.type.c_str(),pokemon_msg.gender);
        loop_rate.sleep();
    }
    return 0;
}

subscriber

#include <ros/ros.h>
#include "learn_topic/Pokemon.h"

void pokemonInfoCallback(const learn_topic::Pokemon::ConstPtr& msg)
{
    ROS_INFO("Subcribe Pokemon Info: name:%s type:%s gender:%d", 
			 msg->name.c_str(), msg->type.c_str(), msg->gender);
}

int main(int argc,char **argv){
    ros::init(argc, argv, "pokemon_sub_topic");
    ros::NodeHandle n;
    ros::Subscriber Sub_Pokemon = n.subscribe<learn_topic::Pokemon>("/pokemon_info",10,pokemonInfoCallback);
    ros::spin();
    return 0;
}

cmake

add_executable(pub_pokemon src/pub_pokemon.cpp)
target_link_libraries(pub_pokemon ${catkin_LIBRARIES})
add_dependencies(pub_pokemon ${PROJECT_NAME}_generate_messages_cpp)

add_executable(sub_pokemon src/sub_pokemon.cpp)
target_link_libraries(sub_pokemon ${catkin_LIBRARIES})
add_dependencies(sub_pokemon ${PROJECT_NAME}_generate_messages_cpp)

python

publisher

import rospy
from learn_topic.msg import Pokemon
def pub_pokemon():
    rospy.init_node('py_pokemon_pub_topic', anonymous=True)
    Pub_Pokemon = rospy.Publisher('/pokemon_info', Pokemon, queue_size=10)
    rate = rospy.Rate(10)

    count = 0

    while not rospy.is_shutdown():
        pokemon_msg = Pokemon()
        pokemon_msg.name = "psyduck"
        pokemon_msg.type = "water"
        pokemon_msg.gender = 2

        Pub_Pokemon.publish(pokemon_msg)
        rospy.loginfo("Publiish pokemon message[%s-%s-%d]",pokemon_msg.name,pokemon_msg.type,pokemon_msg.gender)

        rate.sleep()

if __name__ == '__main__':
    try:
        pub_pokemon()
    except rospy.ROSInterruptException:
        pass

subscriber

import rospy
from learn_topic.msg import Pokemon

def pokemonInfoCallback(msg):
    rospy.loginfo("Subscribe pokemon info: name:%s type:%s gender:%d",
        msg.name,msg.type,msg.gender)

def sub_pokemon():
    rospy.init_node('py_pokemon_sub_topic',anonymous=True)
    rospy.Subscriber('/pokemon_info',Pokemon,pokemonInfoCallback)
    rospy.spin()

if __name__ == '__main__':
    sub_pokemon()