ROS学习笔记（3）之ros的topic发送与接收简单实例
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
#include
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("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
//包含自定义msg产生的头文件
#include
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})