创建一个话题，里面包括学生的姓名性别年龄，并通过发布者发布，订阅者接收

如何定义话题消息

• 定义msg文件
• 在package.xml中添加功能包依赖
• 在CMakeList.txt添加编译选项
• 编译生成语言相关文件

1.定义msg文件

在learning_topic下创建msg文件夹

    在msg文件夹下创建Person.msg文件  

touch Person.msg

  Person.msg内容  

string name
uint8 sex
uint8 age
uint8 unknown=0
uint8 male=1
uint8 female=2

2.在package.xml中添加功能包依赖

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

3.在CMakeList.txt添加编译选项

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)

message_generation

add_message_files(FILES Person.msg)
generate_messages(DEPENDENCIES std_msgs)

4.在learing_topic创建person_publisher.cpp和person_subscriber.cpp文件

touch person_publisher.cpp

  在文件内输入  

/**
 * 该例程将发布/person_info话题，自定义消息类型learning_topic::Person
 */
 
#include <ros/ros.h>
#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
    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;
}

touch person_subscriber.cpp

  在文件内输入  

/**
 * 该例程将订阅/person_info话题，自定义消息类型learning_topic::Person
 */
 
#include <ros/ros.h>
#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
    ros::Subscriber person_info_sub = n.subscribe("/person_info", 10, personInfoCallback);

    // 循环等待回调函数
    ros::spin();

    return 0;
}

5.编译

在catkin_ws文件下打开终端
输入

catkin_make

编译

6.验证

输入

roscore
rosrun learning_topic person_subscriber
rosrun learning_topic person_publisher

当然，三个命令都是在不同终端下执行的。

结果