ROS学习笔记之——消息的订阅与再发布

在进行ros开发时，最基本的就是对消息进行订阅与发布。

在同一个节点里订阅和发布消息

本博文，暂时订阅ROS自带话题/odometry/filtered

并保存到文档中，同时将其发布～

直接给出代码如下

#include
#include 
#include 
#include 
#include 
#include 
#include 
// #include  
// #include 

using namespace std;

class point_time
{
	//定义这个类的私有成员
	private:
		ros::NodeHandle n; 声明用于ROS系统和通信的节点句柄


		double t;
		double t_past;
		double t_now;
		int flag_past;

		//定义订阅者
		ros::Subscriber point_info_sub;

		//定义发布者与订阅者
		ros::Publisher point_info_pub;
		geometry_msgs::PointStamped ekf_point;

		//写入文件流(写入时间的)
		ofstream fout_time;

		//写入文件流(写入坐标的)--用统一的文件流就好
		// ofstream fout_point;


	//公有成员
	public:
		//定义其构造函数
		point_time()
		{
			t_past = 0;
			t_now = 0;
			flag_past = 1;
			t = 0;
			

			fout_time.open("time_odom_multi_location_ekf_xyz.txt");	//打开一个这样的文件

			fout_time << "x" << "\t" << "y" << "\t"<< "z" << "\t"<< "time" << endl;

			//订阅来自/odometry/filtered的话题
			//消息类型为nav_msgs::Odometry
			//通过函数pointCallback来调回
			point_info_sub = n.subscribe("/odometry/filtered", 1000, &point_time::pointCallback, this);
			
			//发布一个名为/location_ekf_info的话题
			//消息类型为geometry_msgs::PointStamped
			point_info_pub=n.advertise("/location_ekf_info", 1000);
		}

		void pointCallback(const nav_msgs::Odometry::ConstPtr &msgPointStamped)
		{
			nav_msgs::Odometry msgPoseStamped = *msgPointStamped;
			//接收到消息后，给到发布者（发布者是私有成员）
			ekf_point.point.x = msgPoseStamped.pose.pose.position.x;
			ekf_point.point.y = msgPoseStamped.pose.pose.position.y;
			ekf_point.point.z = msgPoseStamped.pose.pose.position.z;

			//给发布者的加入frameid和时间戳
			ekf_point.header.frame_id ="map";
			ekf_point.header.stamp = ros::Time::now();
			//在终端显示定位结果与时间
			ROS_INFO("(%.5f, %.5f, %.5f)", msgPoseStamped.pose.pose.position.x*100, msgPoseStamped.pose.pose.position.y*100, msgPoseStamped.pose.pose.position.z*100);
			cout << "coordinate_out_time:\t" << msgPoseStamped.header.stamp << "secs" << endl;
			
			//保存到文件中。
			fout_time << msgPoseStamped.pose.pose.position.x*100 <<"\t"<< msgPoseStamped.pose.pose.position.y*100 <<"\t"<< msgPoseStamped.pose.pose.position.z*100 << "\t";
			point_info_pub.publish(ekf_point);//发布出去

			//将时间差输出出来
			if(flag_past == 1)
			{
				t_past = msgPoseStamped.header.stamp.toSec();
				flag_past = 0;
				// fout_time << t << endl;
			}
			else
			{
				t_now = msgPoseStamped.header.stamp.toSec();
				flag_past = 1;
			}

			if (t_now != 0)
			{
				t = t_now - t_past;
				if (t_now > t_past)
				{
					t = t;
				}
				else
				{
					t = -t;
				}
				cout << "t_now - t_past = " << t << endl;
				fout_time << t << endl;
			}
			else 
			{
				t=0;
				cout << "t_now - t_past = " << t << endl;
				fout_time << t << endl;
			}
		}

		//构析函数
		~point_time()
		{
			fout_time.close();
			cout << "close file success!" << endl;
		}

};

int main(int argc, char **argv)
{
	ros::init(argc, argv, "ekf_translater");//初始化当前节点的名称（这个名字应该需要跟cmake.list设置的一样）
	// ros::NodeHandle n;

	point_time recordT;//定义了一个类

	// ros::Subscriber point_info_sub = n.subscribe("/location_info", 1000, boost::bind(pointCallback,_1, t_past, t_now, flag_past));
	ros::spin();
	return 0;
}

在同一个节点里订阅和发布消息的另外一种方法

ROS 基础: 在同一个节点里订阅和发布消息_知行合一-CSDN博客

#include 
 
class SubscribeAndPublish
{
public:
  SubscribeAndPublish()
  {
    //Topic you want to publish
    pub_ = n_.advertise("/published_topic", 1);
 
    //Topic you want to subscribe
    sub_ = n_.subscribe("/subscribed_topic", 1, &SubscribeAndPublish::callback, this);
  }
 
  void callback(const SUBSCRIBED_MESSAGE_TYPE& input)
  {
    PUBLISHED_MESSAGE_TYPE output;
    //.... do something with the input and generate the output...
    pub_.publish(output);
  }
 
private:
  ros::NodeHandle n_; 
  ros::Publisher pub_;
  ros::Subscriber sub_;
 
}//End of class SubscribeAndPublish
 
int main(int argc, char **argv)
{
  //Initiate ROS
  ros::init(argc, argv, "subscribe_and_publish");
 
  //Create an object of class SubscribeAndPublish that will take care of everything
  SubscribeAndPublish SAPObject;
 
  ros::spin();
 
  return 0;
}