16.ROS编程学习：乌龟背景改变——参数服务器参数“改”

目录

准备工作

c++实现对背景色的修改

 python实现对背景色的修改

准备工作

分开启动ROS Master和乌龟GUI界面，因为之后的操作要改动参数服务器的参数，如果roscore关闭再重启，参数服务器会回到初始状态。

roscore
rosrun turtlesim turtlesim_node 

 列出参数服务器所有参数

rosparam list

rosmelodic@rosmelodic-virtual-machine:~/catkin_ws$ rosparam list
/rosdistro
/roslaunch/uris/host_rosmelodic_virtual_machine__33639
/rosversion
/run_id
/turtlesim/background_b
/turtlesim/background_g
/turtlesim/background_r

如下为背景色的参数的键名。

/turtlesim/background_b
/turtlesim/background_g
/turtlesim/background_r

 如下是背景色参数键名对应的键值。

rosmelodic@rosmelodic-virtual-machine:~/catkin_ws$ rosparam get /turtlesim/background_g
86
rosmelodic@rosmelodic-virtual-machine:~/catkin_ws$ rosparam get /turtlesim/background_b
255
rosmelodic@rosmelodic-virtual-machine:~/catkin_ws$ rosparam get /turtlesim/background_r
69

根据之前的参数服务器学习，改颜色属于对参数服务器的参数“改”，利用的是覆盖的方法。

10.ROS编程学习：参数管理机制c++实现_机械专业的计算机小白的博客-CSDN博客https://blog.csdn.net/wzfafabga/article/details/127413670?spm=1001.2014.3001.550111.ROS编程学习：参数管理机制python实现_机械专业的计算机小白的博客-CSDN博客https://blog.csdn.net/wzfafabga/article/details/127432682?spm=1001.2014.3001.5501

c++实现对背景色的修改

wugui_param_beijing.cpp

#include "ros/ros.h"

/* 
    1.被修改键值的键名：/turtlesim/background_b  /turtlesim/background_g  /turtlesim/background_r
    2.两种方法一种是通过节点句柄，另一种是通过ros::param
*/
int main(int argc, char  *argv[])
{
    // 防止控制台中文乱码
    setlocale(LC_ALL,"");
    // 初始化ROS节点
    ros::init(argc,argv,"wugui_beijing_set");
    // 初始化节点句柄
    ros::NodeHandle n;
    // 通过节点句柄修改参数服务器参数(第一次覆盖),背景白色
    n.setParam("/turtlesim/background_b",255);
    n.setParam("/turtlesim/background_g",255);
    n.setParam("/turtlesim/background_r",255);
    // 通过ros::param修改参数服务器参数(第二次覆盖),背景黑色
    ros::param::set("/turtlesim/background_b",0);
    ros::param::set("/turtlesim/background_g",0);
    ros::param::set("/turtlesim/background_r",0); 
    return 0; 
}

 这个程序首先将背景改为白色，然后又将背景改为黑色。

CMakeList.txt配置

add_executable(wugui_param_beijing src/wugui_param_beijing.cpp)
add_dependencies(wugui_param_beijing ${${PROJECT_NAME}_EXPORTED_TARGETS} ${catkin_EXPORTED_TARGETS})
target_link_libraries(wugui_param_beijing
  ${catkin_LIBRARIES}
)

编译

catkin_make

启动ROS Master

roscore

启动改参数的可执行文件节点

rosmelodic@rosmelodic-virtual-machine:~/catkin_ws$ source ./devel/setup.bash 
rosmelodic@rosmelodic-virtual-machine:~/catkin_ws$ rosrun wugui_ttest wugui_param_beijing 

查看修改情况

rosmelodic@rosmelodic-virtual-machine:~/catkin_ws$ rosparam get /turtlesim/background_b
0
rosmelodic@rosmelodic-virtual-machine:~/catkin_ws$ rosparam get /turtlesim/background_g
0
rosmelodic@rosmelodic-virtual-machine:~/catkin_ws$ rosparam get /turtlesim/background_r
0

启动乌龟GUI

rosrun turtlesim turtlesim_node 

结果

问题

依次手动启动各种节点很麻烦，而且将修改背景颜色的节点直接加入launch文件会出现问题，因为launch文件中的各个节点没有启动顺序，故要利用到launch的参数设置功能。

主要部分

 注意的是这次的node节点加入了尾，这是为了把指向turtlesim中的参数。

还有注意报错：

RLException: Invalid roslaunch XML syntax: mismatched tag: line ？？？, column ？？？
The traceback for the exception was written to the log file

ROS改错：launch文件中标签的结束符号问题_机械专业的计算机小白的博客-CSDN博客https://blog.csdn.net/wzfafabga/article/details/127514851?csdn_share_tail=%7B%22type%22%3A%22blog%22%2C%22rType%22%3A%22article%22%2C%22rId%22%3A%22127514851%22%2C%22source%22%3A%22wzfafabga%22%7D

启动launch文件

roslaunch wugui_ttest wugui_start.launch 

 python实现对背景色的修改

wugui_param_beijing_p.py

#! /usr/bin/env python
# -*- coding: UTF-8 -*-

import rospy

if __name__ == "__main__":
    # 初始化ROS节点
    rospy.init_node("wugui_beijing_p")
    # 通过rospy.set_param调节参数
    rospy.set_param("/turtlesim/background_r",255)
    rospy.set_param("/turtlesim/background_g",255)
    rospy.set_param("/turtlesim/background_b",255)

添加可执行权限

chmod +x *.py

CMakeList.txt配置

catkin_install_python(PROGRAMS
  scripts/wugui_param_beijing_p.py
  DESTINATION ${CATKIN_PACKAGE_BIN_DESTINATION}
)

依次启动

roscore

rosrun wugui_ttest wugui_param_beijing_p.py 

rosrun turtlesim turtlesim_node