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ROS学习笔记（3）之ros的topic发送与接收简单实例

程序员文章站 2022-07-12 09:49:41
...

建立package

cd ~/catkin_ws/src   
catkin_create_pkg first_pkg roscpp ros_py std_msgs

编辑msg文件

cd first_pkg
mkdir msg#创建msg文件夹,这个文件夹一定要是这个名字
cd msg #进入文件夹
vi test_1.msg //怎么编译这个文件，根据跟人喜好

,msg文件中的代码：

float32 x
float32 y
string state

这里的数据类型是ros自己定义的，都在std_msgs中，与传统的cpp中的有一定出入。

编写c++源文件

源文件都写在first_pkg/src中

talker.cpp

#include<ros/ros.h>
#include<first_pkg/text_1.h>

int main(int argc,char** argv){
    ros::init(argc,argv,"talker");//节点初始化
    ros::NodeHandle nh; //定义节点的句柄，实例化节点。
    first_pkg::text_1 msg ;//定义msg变量，类型为topic_demo命名空间下的gps
    msg.x=1.0;
    msg.y=1.0;
    msg.state="working";//定义变量的值
    //创建publisher
    ros::Publisher pub = nh.advertise<first_pkg::text_1>("test_1_info", 1); 
    //first_pkg::text_1话题传送的信息格式
    //("test_1_info", 1)话题的名字，缓存队列
    //定义发布的频率 
    ros::Rate loop_rate(1.0); //循环发送的频率为1，即一秒钟1次
    while (ros::ok())
    {
        //以指数增长，每隔1秒更新一次
        msg.x = 1.03 * msg.x ;
        msg.y = 1.01 * msg.y;
        ROS_INFO("msg.x = %f,msg.y = %f,msg.state = %s",msg.x,msg.y,msg.state.c_str());
        //将当前的信息打印处理，类似于printf。
        //c_str()将std_msgs::string转换为std::string
        //以1Hz的频率发布msg
        pub.publish(msg);
        //根据前面定义的频率, sleep 1s
        loop_rate.sleep();//根据前面的定义的loop_rate,设置1s的暂停
    }

    return 0;
}

listen.cpp

//ROS头文件
#include <ros/ros.h>
//包含自定义ms*生的头文件
#include<first_pkg/text_1.h>

void Callback(const first_pkg::text_1::ConstPtr& msg_p)
//topic_demo::gps::ConstPtr为gps.msg文件编译生成的头文件中定义的数据类型，是一个常指针。
{  
    ROS_INFO("msg.x = %f,msg.y = %f,msg.state = %s",msg_p->x,msg_p->y,msg_p->state.c_str());
}

int main(int argc, char **argv)
{
  ros::init(argc, argv, "listener");//初始化，且节点名为listener
  ros::NodeHandle n; //节点句柄为n
  ros::Subscriber sub = n.subscribe("test_1_info", 1, Callback);
   //gpsCallback为回调函数，即当Subscriber接收到信息后，会调用回调函数进行处理。
   //gps_info为接收到的msg，1为缓冲队列的长度。
  ros::spin(); 
  //ros::spin()用于调用所有可触发的回调函数。
  //反复循环检测与调用，若缓存队列中含有msg，则会通过回调函数进行处理，而队列中没有msg，
  //则不会进行回调。相当于一个循环。是阻塞的。
  //类似于在循环里反复调用ros::spinOnce()。ros::spinOnce()是指检测并调用回调函数一次。
  return 0;
}

修改MackList.txt

.xml文件不需要修改

#版本
cmake_minimum_required(VERSION 2.8.3)
#功能包名
project(first_pkg)

## Compile as C++11, supported in ROS Kinetic and newer
# add_compile_options(-std=c++11)

## Find catkin macros and libraries
## if COMPONENTS list like find_package(catkin REQUIRED COMPONENTS xyz)
## is used, also find other catkin packages
#依赖包
find_package(catkin REQUIRED COMPONENTS
  roscpp
  std_msgs
  message_generation #用于将我们写的.msg文件转换成头文件
)

## System dependencies are found with CMake's conventions
# find_package(Boost REQUIRED COMPONENTS system)


## Uncomment this if the package has a setup.py. This macro ensures
## modules and global scripts declared therein get installed
## See http://ros.org/doc/api/catkin/html/user_guide/setup_dot_py.html
# catkin_python_setup()

################################################
## Declare ROS messages, services and actions ##
################################################

## To declare and build messages, services or actions from within this
## package, follow these steps:
## * Let MSG_DEP_SET be the set of packages whose message types you use in
##   your messages/services/actions (e.g. std_msgs, actionlib_msgs, ...).
## * In the file package.xml:
##   * add a build_depend tag for "message_generation"
##   * add a build_depend and a exec_depend tag for each package in MSG_DEP_SET
##   * If MSG_DEP_SET isn't empty the following dependency has been pulled in
##     but can be declared for certainty nonetheless:
##     * add a exec_depend tag for "message_runtime"
## * In this file (CMakeLists.txt):
##   * add "message_generation" and every package in MSG_DEP_SET to
##     find_package(catkin REQUIRED COMPONENTS ...)
##   * add "message_runtime" and every package in MSG_DEP_SET to
##     catkin_package(CATKIN_DEPENDS ...)
##   * uncomment the add_*_files sections below as needed
##     and list every .msg/.srv/.action file to be processed
##   * uncomment the generate_messages entry below
##   * add every package in MSG_DEP_SET to generate_messages(DEPENDENCIES ...)

## Generate messages in the 'msg' folder
#产生自定义msg
add_message_files(
  FILES
  text_1.msg
 )

## Generate services in the 'srv' folder
# add_service_files(
#   FILES
#   Service1.srv
#   Service2.srv
# )

## Generate actions in the 'action' folder
# add_action_files(
#   FILES
#   Action1.action
#   Action2.action
# )

## Generate added messages and services with any dependencies listed here
#产生自定义msg，所需要的依赖
generate_messages(
  DEPENDENCIES
  std_msgs
)

################################################
## Declare ROS dynamic reconfigure parameters ##
################################################

## To declare and build dynamic reconfigure parameters within this
## package, follow these steps:
## * In the file package.xml:
##   * add a build_depend and a exec_depend tag for "dynamic_reconfigure"
## * In this file (CMakeLists.txt):
##   * add "dynamic_reconfigure" to
##     find_package(catkin REQUIRED COMPONENTS ...)
##   * uncomment the "generate_dynamic_reconfigure_options" section below
##     and list every .cfg file to be processed

## Generate dynamic reconfigure parameters in the 'cfg' folder
# generate_dynamic_reconfigure_options(
#   cfg/DynReconf1.cfg
#   cfg/DynReconf2.cfg
# )

###################################
## catkin specific configuration ##
###################################
## The catkin_package macro generates cmake config files for your package
## Declare things to be passed to dependent projects
## INCLUDE_DIRS: uncomment this if your package contains header files
## LIBRARIES: libraries you create in this project that dependent projects also need
## CATKIN_DEPENDS: catkin_packages dependent projects also need
## DEPENDS: system dependencies of this project that dependent projects also need
catkin_package(
#  INCLUDE_DIRS include
#  LIBRARIES first_pkg
#  CATKIN_DEPENDS roscpp std_msgs
#  DEPENDS system_lib
)

###########
## Build ##
###########

## Specify additional locations of header files
## Your package locations should be listed before other locations
#保证topic可以被其他package收听到，这里也可以不用
include_directories(
 include
  ${catkin_INCLUDE_DIRS}
)

## Declare a C++ library
# add_library(${PROJECT_NAME}
#   src/${PROJECT_NAME}/first_pkg.cpp
# )

## Add cmake target dependencies of the library
## as an example, code may need to be generated before libraries
## either from message generation or dynamic reconfigure
# add_dependencies(${PROJECT_NAME} ${${PROJECT_NAME}_EXPORTED_TARGETS} ${catkin_EXPORTED_TARGETS})

## Declare a C++ executable
## With catkin_make all packages are built within a single CMake context
## The recommended prefix ensures that target names across packages don't collide
# add_executable(${PROJECT_NAME}_node src/first_pkg_node.cpp)

## Rename C++ executable without prefix
## The above recommended prefix causes long target names, the following renames the
## target back to the shorter version for ease of user use
## e.g. "rosrun someones_pkg node" instead of "rosrun someones_pkg someones_pkg_node"
# set_target_properties(${PROJECT_NAME}_node PROPERTIES OUTPUT_NAME node PREFIX "")

## Add cmake target dependencies of the executable
## same as for the library above
# add_dependencies(${PROJECT_NAME}_node ${${PROJECT_NAME}_EXPORTED_TARGETS} ${catkin_EXPORTED_TARGETS})

## Specify libraries to link a library or executable target against
# target_link_libraries(${PROJECT_NAME}_node
#   ${catkin_LIBRARIES}
# )

#############
## Install ##
#############

# all install targets should use catkin DESTINATION variables
# See http://ros.org/doc/api/catkin/html/adv_user_guide/variables.html

## Mark executable scripts (Python etc.) for installation
## in contrast to setup.py, you can choose the destination
# install(PROGRAMS
#   scripts/my_python_script
#   DESTINATION ${CATKIN_PACKAGE_BIN_DESTINATION}
# )

## Mark executables and/or libraries for installation
# install(TARGETS ${PROJECT_NAME} ${PROJECT_NAME}_node
#   ARCHIVE DESTINATION ${CATKIN_PACKAGE_LIB_DESTINATION}
#   LIBRARY DESTINATION ${CATKIN_PACKAGE_LIB_DESTINATION}
#   RUNTIME DESTINATION ${CATKIN_PACKAGE_BIN_DESTINATION}
# )

## Mark cpp header files for installation
# install(DIRECTORY include/${PROJECT_NAME}/
#   DESTINATION ${CATKIN_PACKAGE_INCLUDE_DESTINATION}
#   FILES_MATCHING PATTERN "*.h"
#   PATTERN ".svn" EXCLUDE
# )

## Mark other files for installation (e.g. launch and bag files, etc.)
# install(FILES
#   # myfile1
#   # myfile2
#   DESTINATION ${CATKIN_PACKAGE_SHARE_DESTINATION}
# )

#############
## Testing ##
#############

## Add gtest based cpp test target and link libraries
# catkin_add_gtest(${PROJECT_NAME}-test test/test_first_pkg.cpp)
# if(TARGET ${PROJECT_NAME}-test)
#   target_link_libraries(${PROJECT_NAME}-test ${PROJECT_NAME})
# endif()

## Add folders to be run by python nosetests
# catkin_add_nosetests(test)
#生成可执行文件
add_executable(talker ./src/talker.cpp)
target_link_libraries(talker ${catkin_LIBRARIES})
add_executable(listener ./src/listener.cpp)
target_link_libraries(listener ${catkin_LIBRARIES})

 

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