定义msg文件

//在文件夹learning_topic中新建一个命名为msg的文件夹,存放消息类文件,方便管理
//创建.msg文件 touch Person.msg
//打开该文件,输入以下信息后保存
string name
uint8 sex
uint8 age

uint8 unknown = 0
uint8 male = 1
uint8 female = 2
//这里写的并不是cpp,也不是python。但他在编译过程中会由ros自动编译成cpp或python

在package.xml中添加功能包依赖

//打开文件夹learning_topic,打开package.xml
//gedit package.xml
//保存到最下方/<build_depend>类中
<build_depend>message_generation</build_depend>
<exec_depend>message_runtime</exec_depend>
//<build_depend>用于添加编译依赖,这里添加message_generation功能包
//<exec_depend<用于添加执行依赖,这里添加message_runtime功能包

在CMakeLists.txt添加编译选项

//打开文件夹learning_topic,打开CMakeLists.txt。
//在最上方的find_package中添加以下语句
message_generation
//找到Declare ROS dynamic reconfigure parameters的位置,在上方添加以下语句
add_message_files(FILES Person.msg)
generate_messages(DEPENDENCIES std_msgs)
//第一句,告诉编译器Person.msg是我们定义的消息接口
//第二句,告诉编译器在编译Person.msg文件的时候,需要依赖ROS哪些已有的库或者包。
//找到catkin specific configuration(即Build上方),添加以下语句
CATKIN_DEPENDS geometry_msgs roscpp rospy std_msgs turtlesim message_runtime

编译生成语言相关文件

//回到工作空间的根目录catkin_ws下,打开命令行,尝试进行编译。输入指令
catkin_make

创建publisher和subscriber

//person_publisher.cpp
/**
 * 该例程将发布/person_info话题,自定义消息类型learning_topic::Person
 */
 
#include <ros/ros.h>
//!!!!!关键!!!!!
#include "learning_topic/Person.h"

int main(int argc, char **argv)
{
    // ROS节点初始化
    ros::init(argc, argv, "person_publisher");

    // 创建节点句柄
    ros::NodeHandle n;

    // 创建一个Publisher,发布名为/person_info的topic,消息类型为learning_topic::Person,队列长度10
    //!!!!!关键!!!!!
    ros::Publisher person_info_pub = n.advertise<learning_topic::Person>("/person_info", 10);

    // 设置循环的频率
    ros::Rate loop_rate(1);

    int count = 0;
    while (ros::ok())
    {
        // 初始化learning_topic::Person类型的消息
        learning_topic::Person person_msg;
        person_msg.name = "Tom";
        person_msg.age  = 18;
        person_msg.sex  = learning_topic::Person::male;

        // 发布消息
        person_info_pub.publish(person_msg);

        ROS_INFO("Publish Person Info: name:%s  age:%d  sex:%d", 
                  person_msg.name.c_str(), person_msg.age, person_msg.sex);

        // 按照循环频率延时
        loop_rate.sleep();
    }

    return 0;
}

//person_subscriber.cpp
/**
 * 该例程将订阅/person_info话题,自定义消息类型learning_topic::Person
 */
 
#include <ros/ros.h>
//!!!!!关键!!!!!
#include "learning_topic/Person.h"

// 接收到订阅的消息后,会进入消息回调函数
void personInfoCallback(const learning_topic::Person::ConstPtr& msg)
{
    // 将接收到的消息打印出来
    ROS_INFO("Subcribe Person Info: name:%s  age:%d  sex:%d", 
             msg->name.c_str(), msg->age, msg->sex);
}

int main(int argc, char **argv)
{
    // 初始化ROS节点
    ros::init(argc, argv, "person_subscriber");

    // 创建节点句柄
    ros::NodeHandle n;

    // 创建一个Subscriber,订阅名为/person_info的topic,注册回调函数personInfoCallback
    //!!!!!关键!!!!!
    ros::Subscriber person_info_sub = n.subscribe("/person_info", 10, personInfoCallback);

    // 循环等待回调函数
    ros::spin();

    return 0;
}

配置CMakeLists.txt中的编译规则
*设置需要编译的代码和生成的可执行文件;
*设置链接库;
*添加依赖项.

//这里相比之前配置CMakeLists.txt,多了add_dependencies的语句目的是让可执行文件(前两句做的工作)和动态生成的文件产生依赖关系
//位置依旧,找到Install位置的上方,添加以下语句,保存.
add_executable(person_publisher src/person_publisher.cpp)
target_link_libraries(person_publisher ${catkin_LIBRARIES})
add_dependencies(person_publisher ${PROJECT_NAME}_generate_messages_cpp)

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


编译并运行publisher和subscriber

cd ~/catkin_ws
catkin_make
source devel/setup.bash
roscore
//新开一个终端,运行subscriber
rosrun learning_topic person_subscriber
//新开一个终端,运行publisher
rosrun learning_topic person_publisher
//ROS Master是帮助节点的创建和链接的。节点一旦创建和链接后,就不受ROS Master影响

publisher和subscriber(python)

#!/usr/bin/env python
# -*- coding: utf-8 -*-
# 该例程将发布/person_info话题,自定义消息类型learning_topic::Person

import rospy
from learning_topic.msg import Person

def velocity_publisher():
    # ROS节点初始化
    rospy.init_node('person_publisher', anonymous=True)

    # 创建一个Publisher,发布名为/person_info的topic,消息类型为learning_topic::Person,队列长度10
    person_info_pub = rospy.Publisher('/person_info', Person, queue_size=10)

    #设置循环的频率
    rate = rospy.Rate(10) 

    while not rospy.is_shutdown():
        # 初始化learning_topic::Person类型的消息
        person_msg = Person()
        person_msg.name = "Tom";
        person_msg.age  = 18;
        person_msg.sex  = Person.male;

        # 发布消息
        person_info_pub.publish(person_msg)
        rospy.loginfo("Publsh person message[%s, %d, %d]", 
                person_msg.name, person_msg.age, person_msg.sex)

        # 按照循环频率延时
        rate.sleep()

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

#!/usr/bin/env python
# -*- coding: utf-8 -*-
# 该例程将订阅/person_info话题,自定义消息类型learning_topic::Person

import rospy
from learning_topic.msg import Person

def personInfoCallback(msg):
    rospy.loginfo("Subcribe Person Info: name:%s  age:%d  sex:%d", 
             msg.name, msg.age, msg.sex)

def person_subscriber():
    # ROS节点初始化
    rospy.init_node('person_subscriber', anonymous=True)

    # 创建一个Subscriber,订阅名为/person_info的topic,注册回调函数personInfoCallback
    rospy.Subscriber("/person_info", Person, personInfoCallback)

    # 循环等待回调函数
    rospy.spin()

if __name__ == '__main__':
    person_subscriber()