ROS之创建发布者代码和订阅者代码

╰+攻爆jí腚メ 2023-06-24 15:25 3阅读 0赞

## 如何实现一个发布者 ##

首先要创建一个功能包用于存放该代码文件，  
创建教程:[https://blog.csdn.net/CCCrunner/article/details/103656906][https_blog.csdn.net_CCCrunner_article_details_103656906]

catkin_create_pkg learning_topic roscpp rospy geometry_msgs turtlesim std_msgs

![在这里插入图片描述][20200110173351704.png]  
**发布者代码思路**

*  初始化ROS节点
 *  向ROS Master注册节点信息，包括发布的话题名和话题中的消息类型
 *  创建消息数据
 *  按照一定频率循环发布消息

文件存在位置为：`工作空间/src/功能包名字/src`  
如下图所示：  
![在这里插入图片描述][20200110173933583.png]  
**velocity\_publisher.cpp**

/**
     * 该例程将发布turtle1/cmd_vel话题，消息类型geometry_msgs::Twist
     */
     
    #include <ros/ros.h>
    #include <geometry_msgs/Twist.h>
    
    int main(int argc, char **argv)
    {
        
    	// ROS节点初始化
    	ros::init(argc, argv, "velocity_publisher");
    
    	// 创建节点句柄
    	ros::NodeHandle n;
    
    	// 创建一个Publisher，发布名为/turtle1/cmd_vel的topic，消息类型为geometry_msgs::Twist，队列长度10
    	ros::Publisher turtle_vel_pub = n.advertise<geometry_msgs::Twist>("/turtle1/cmd_vel", 10);
    
    	// 设置循环的频率
    	ros::Rate loop_rate(10);
    
    	int count = 0;
    	while (ros::ok())
    	{
        
    	    // 初始化geometry_msgs::Twist类型的消息
    		geometry_msgs::Twist vel_msg;
    		vel_msg.linear.x = 0.5;
    		vel_msg.angular.z = 0.2;
    
    	    // 发布消息
    		turtle_vel_pub.publish(vel_msg);
    		ROS_INFO("Publsh turtle velocity command[%0.2f m/s, %0.2f rad/s]", 
    				vel_msg.linear.x, vel_msg.angular.z);
    	    // 按照循环频率延时
    	    loop_rate.sleep();
    	}
    	return 0;
    }

最后需要配置`CMakeList.txt`中的编译规则

*  需要配置编译的代码和生成的可执行文件  
    编译命令如下：  
    `add_executable(编译后的名称 编译文件路径)`  
    实例如下：  
    `add_executable(velocity_publisher src/velocity_publisher.cpp)`
 *  设置链接库  
    编译命令如下：  
    `target_link_libraries(编译后的名称 ${catkin_LIBRARIES})`  
    实例如下：  
    `target_link_libraries(velocity_publisher ${catkin_LIBRARIES})`  
    ![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9kcXdhbmcuYmxvZy5jc2RuLm5ldA_size_16_color_FFFFFF_t_70]  
    最后，退到工作空间的目录下，`open Terminal`,`cd catkin_ws`,`catkin_make`,效果如下图:  
    ![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9kcXdhbmcuYmxvZy5jc2RuLm5ldA_size_16_color_FFFFFF_t_70 1]  
    最后开始展示代码执行的效果：

1.  新开一个终端，输入`roscore`

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9kcXdhbmcuYmxvZy5jc2RuLm5ldA_size_16_color_FFFFFF_t_70 2]  
2. `rosrun turtlesim turtlesim_node`,运行一个turtle机器人。  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9kcXdhbmcuYmxvZy5jc2RuLm5ldA_size_16_color_FFFFFF_t_70 3]

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9kcXdhbmcuYmxvZy5jc2RuLm5ldA_size_16_color_FFFFFF_t_70 4]  
3. 在运行重要代码之前，先编译一下`source ~/catkin/devel/setup.zsh`,如果你的shell是默认的bash,那么你就运行`source ~/catkin/devel/setup.bash`  
4. 重点代码来了，运行这个成功，就说明你的publisher代码编写成功。`rosrun learning_topic velocity_publisher`  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9kcXdhbmcuYmxvZy5jc2RuLm5ldA_size_16_color_FFFFFF_t_70 5]  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9kcXdhbmcuYmxvZy5jc2RuLm5ldA_size_16_color_FFFFFF_t_70 6]  
接下来我们要实现的的就是订阅者

## 如何实现一个订阅者 ##

首先，我们需要在`工作空间/src/功能包/src/`，如实例`catkin_ws/src/learning_topic/src`目录下。  
输入`gedit pose_velocity.cpp`来编写订阅者代码，代码如下所示:

#include <ros/ros.h>
    #include "turtlesim/Pose.h"
    void poseCallback(const turtlesim::Pose::ConstPtr& msg)
    {
    	ROS_INFO("turtle subscribe [%.2f]",msg->x);
    }
    
    int main(int argc,char **argv)
    {
    	ros::init(argc,argv,"pose_subscriber");
    	ros::NodeHandle n;
    	ros::Subscriber pose_sub = n.subscribe("/turtle1/pose",10,poseCallback);
    	ros::spin();
    	return 0;
    }

然后编译`CMakeList.txt`文件  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9kcXdhbmcuYmxvZy5jc2RuLm5ldA_size_16_color_FFFFFF_t_70 7]  
最后退到工作目录下，输入`catkin_make`进行编译

然后输入`roscore`启动ros master  
输入`rosrun turtlesim turtlesim_node`启动乌龟节点  
输入`source ~/catkin_ws/devel/setup.zsh`进行编译  
输入`rosrun learning_topic pose_subscriber`进行订阅乌龟节点的Twist信息  
如下图所示:  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9kcXdhbmcuYmxvZy5jc2RuLm5ldA_size_16_color_FFFFFF_t_70 8]

[https_blog.csdn.net_CCCrunner_article_details_103656906]: https://blog.csdn.net/CCCrunner/article/details/103656906
[20200110173351704.png]: https://img-blog.csdnimg.cn/20200110173351704.png
[20200110173933583.png]: https://img-blog.csdnimg.cn/20200110173933583.png
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