ROS.2 消息订阅接收

1、创建目录

mkdir aa
mkdir aa/src
cd aa/src
catkin_init_workspace #src目录下
cd ..
catkin_make  #src上一级执行

目录结束

加入到环境变量

source devel/setup.bash
echo $ROS_PACKAGE_PATH
#/root/catkin_ws/src:/opt/ros/melodic/share

devel文件结构，放置编译生成的可执行文件

2、创建包

进入src目录
cd aa/src
catkin_create_pkg learning2 std_msgs rospy roscpp

创建成功后会在src目录下生成learning2 的文件夹结构

查找功能包

rospack find turtlesim 
/opt/ros/melodic/share/turtlesim

3、消息发送订阅

http://wiki.ros.org/cn/ROS/Tutorials/WritingPublisherSubscriber%28python%29
在功能包的src目录下创建

#!/usr/bin/env python
# license removed for brevity
# talker.py 消息发送
# chmod +x talker.py 注意执行否则无法运行
import rospy
from std_msgs.msg import String
 
def talker():
     pub = rospy.Publisher('chatter', String, queue_size=10)
     rospy.init_node('talker', anonymous=True)
     rate = rospy.Rate(10) # 10hz
     while not rospy.is_shutdown():
           hello_str = "hello world %s" % rospy.get_time()
           rospy.loginfo(hello_str)
           pub.publish(hello_str)
           rate.sleep()
   
if __name__ == '__main__':
       try:
           talker()
       except rospy.ROSInterruptException:
           pass

#!/usr/bin/env python
# listener.py 消息接收
# chmod +x talker.py
import rospy
from std_msgs.msg import String
 
def callback(data):
     rospy.loginfo(rospy.get_caller_id() + "I heard %s", data.data)
     
def listener():
 
     # In ROS, nodes are uniquely named. If two nodes with the same
     # node are launched, the previous one is kicked off. The
     # anonymous=True flag means that rospy will choose a unique
     # name for our 'listener' node so that multiple listeners can
     # run simultaneously.
     rospy.init_node('listener', anonymous=True)
 
     rospy.Subscriber("chatter", String, callback)
 
     # spin() simply keeps python from exiting until this node is stopped
     rospy.spin()
 
if __name__ == '__main__':
     listener()

rqt_graph

查看消息

image.png

#!/usr/bin/env python
# -*- coding: UTF-8 -*-
import rospy
from std_msgs.msg import String
import time
import sys
def _publish():
    rospy.init_node("Ppublish",anonymous=True)
    rpy=rospy.Publisher("chatter",String,queue_size=10)
    rate = rospy.Rate(10) 
    while not rospy.is_shutdown():
        print("loop...")
        rpy.publish("aaa")
        rate.sleep()

def _listener():
    rospy.init_node("Llistener",anonymous=True)
    rospy.Subscriber("chatter",String,lambda str:rospy.loginfo(str))
    rospy.spin()

if __name__ == "__main__":
    try:
        arg1=sys.argv[1]
        print(arg1)
        x = int(arg1)
        if x==1:
            _publish()
        else:
            _listener()
    except Exception as err:
        rospy.loginfo("err") #为何为不显示出来呀
        print(err)
        print("请输入参数")

turtlesim 乌龟事件的

https://gitee.com/hupinghit/ros_21_tutorials.git

<launch>

    <param name="/turtle_number"   value="2"/>

    <node pkg="turtlesim" type="turtlesim_node" name="turtlesim_node">
        <param name="turtle_name1"   value="Tom"/>
        <param name="turtle_name2"   value="Jerry"/>

        <rosparam file="$(find learning_launch)/config/param.yaml" command="load"/>
    </node>

    <node pkg="turtlesim" type="turtle_teleop_key" name="turtle_teleop_key" output="screen"/>

</launch>

image.png

#!/usr/bin/env python
# -*- coding: utf-8 -*-
# 该例程将发布turtle1/cmd_vel话题，消息类型geometry_msgs::Twist

import rospy
from geometry_msgs.msg import Twist

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

    # 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
    turtle_vel_pub = rospy.Publisher('/turtle1/cmd_vel', Twist, queue_size=10)

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

    while not rospy.is_shutdown():
        # 初始化geometry_msgs::Twist类型的消息
        vel_msg = Twist()
        vel_msg.linear.x = 0.5  #线速度
        vel_msg.angular.z = 0.2  #角速度  一直画圈

        # 发布消息
        turtle_vel_pub.publish(vel_msg)
        rospy.loginfo("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
        rate.sleep()

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

接收

#!/usr/bin/env python
# -*- coding: utf-8 -*-
# 该例程将订阅/turtle1/pose话题，消息类型turtlesim::Pose

import rospy
from turtlesim.msg import Pose

def poseCallback(msg):
    rospy.loginfo("Turtle pose: x:%0.6f, y:%0.6f", msg.x, msg.y)

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

    # 创建一个Subscriber，订阅名为/turtle1/pose的topic，注册回调函数poseCallback
    rospy.Subscriber("/turtle1/pose", Pose, poseCallback)

    # 循环等待回调函数
    rospy.spin()

if __name__ == '__main__':
    pose_subscriber()