0.1ROS2机器人编程简述新书推荐-A Concise Introduction to Robot Programming with ROS2
1.1ROS2机器人编程简述humble-第一章-Introduction
2.1ROS2机器人编程简述humble-第二章-First Steps with ROS2 .1
2.2主要内容是全手工创建一个最简单的自定义节点，其实没啥具体功能，主要是对ROS2节点结构有个更好的理解吧。
使用ros2 pkg create这个命令。
其实-h看一下非常清晰明了。
ros2 pkg create -husage: ros2 pkg create [-h] [--package-format {2,3}] [--description DESCRIPTION] [--license LICENSE] [--destination-directory DESTINATION_DIRECTORY] [--build-type {cmake,ament_cmake,ament_python}] [--dependencies DEPENDENCIES [DEPENDENCIES ...]] [--maintainer-email MAINTAINER_EMAIL] [--maintainer-name MAINTAINER_NAME] [--node-name NODE_NAME] [--library-name LIBRARY_NAME] package_nameCreate a new ROS 2 packagepositional arguments: package_name The package nameoptions: -h, --help show this help message and exit --package-format {2,3}, --package_format {2,3} The package.xml format. --description DESCRIPTION The description given in the package.xml --license LICENSE The license attached to this package; this can be an arbitrary string, but a LICENSE file will only be generated if it is one of the supported licenses (pass '?' to get a list) --destination-directory DESTINATION_DIRECTORY Directory where to create the package directory --build-type {cmake,ament_cmake,ament_python} The build type to process the package with --dependencies DEPENDENCIES [DEPENDENCIES ...] list of dependencies --maintainer-email MAINTAINER_EMAIL email address of the maintainer of this package --maintainer-name MAINTAINER_NAME name of the maintainer of this package --node-name NODE_NAME name of the empty executable --library-name LIBRARY_NAME name of the empty library
创建一个需要 rclcpp std_msgs，节点名为simple_node，功能包名为my_package的命令如下：
ros2 pkg create my package --dependencies rclcpp std_msgs --node-name simple_node
ros2 pkg create my_package --dependencies rclcpp std_msgs --node-name simple_nodegoing to create a new packagepackage name: my_packagedestination directory: /home/zhangrelay/ros_ws/book_ros2/srcpackage format: 3version: 0.0.0description: TODO: Package descriptionmaintainer: ['zhangrelay <zhangrelay@todo.todo>']licenses: ['TODO: License declaration']build type: ament_cmakedependencies: ['rclcpp', 'std_msgs']node_name: simple_nodecreating folder ./my_packagecreating ./my_package/package.xmlcreating source and include foldercreating folder ./my_package/srccreating folder ./my_package/include/my_packagecreating ./my_package/CMakeLists.txtcreating ./my_package/src/simple_node.cpp
这些都是自动生成的，非常方便，当然也有图形化IDE更加方便使用，后续补充。
tree my_package/my_package/├── CMakeLists.txt├── include│ └── my_package├── package.xml└── src └── simple_node.cpp3 directories, 3 filespackage.xml
<?xml version="1.0"?><?xml-model href="http://download.ros.org/schema/package_format3.xsd" schematypens="http://www.w3.org/2001/XMLSchema"?><package format="3"> <name>my_package</name> <version>0.0.0</version> <description>TODO: Package description</description> <maintainer email="zhangrelay@todo.todo">zhangrelay</maintainer> <license>TODO: License declaration</license> <buildtool_depend>ament_cmake</buildtool_depend> <depend>rclcpp</depend> <depend>std_msgs</depend> <test_depend>ament_lint_auto</test_depend> <test_depend>ament_lint_common</test_depend> <export> <build_type>ament_cmake</build_type> </export></package>
simple_node.cpp
#include <cstdio>int main(int argc, char ** argv){ (void) argc; (void) argv; printf("hello world my_package package\n"); return 0;}
参考案例:
#include "rclcpp/rclcpp.hpp"int main(int argc, char * argv[]) { rclcpp::init(argc, argv); auto node = rclcpp::Node::make_shared("simple_node"); rclcpp::spin(node); rclcpp::shutdown(); return 0;}
•#include“rclcpp/rrcpp.hpp”允许访问C++中的大多数ROS2类型和函数。
•rclcpp::init（argc，argv）从启动此进程的参数中提取ROS2应考虑的任何选项。
•第6行创建ROS2节点。node是名称为simplenode的ROS2节点的std::shared_ptr。
rclcpp::Node类配备了许多别名和静态函数，以简化代码。SharedPtr是std::shared-ptr＜rclcppNode＞的别名，
make shared是std:：make shared＜rclcpp::Node＞的静态方法。
以下行是等效的：
std::shared_ptr<rclcpp::Node> node = std::shared_ptr<rclcpp::Node>(new rclcpp::Node("simple_node"));std::shared_ptr<rclcpp::Node> node = std::make_shared<rclcpp::Node>("simple_node");rclcpp::Node::SharedPtr node = std::make_shared<rclcpp::Node>("simple_node");auto node = std::make_shared<rclcpp::Node>("simple_node");auto node = rclcpp::Node::make_shared("simple_node");•在此代码中，spin阻止程序的执行，因此不会立即终止。其重要功能将在后续示例中解释。
•shutdown管理在下一行程序结束之前节点的关闭。
CMakelist.txt
cmake_minimum_required(VERSION 3.8)project(my_package)if(CMAKE_COMPILER_IS_GNUCXX OR CMAKE_CXX_COMPILER_ID MATCHES "Clang") add_compile_options(-Wall -Wextra -Wpedantic)endif()# find dependenciesfind_package(ament_cmake REQUIRED)find_package(rclcpp REQUIRED)find_package(std_msgs REQUIRED)add_executable(simple_node src/simple_node.cpp)target_include_directories(simple_node PUBLIC $<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}/include> $<INSTALL_INTERFACE:include>)target_compile_features(simple_node PUBLIC c_std_99 cxx_std_17) # Require C99 and C++17ament_target_dependencies( simple_node "rclcpp" "std_msgs")install(TARGETS simple_node DESTINATION lib/${PROJECT_NAME})if(BUILD_TESTING) find_package(ament_lint_auto REQUIRED) # the following line skips the linter which checks for copyrights # comment the line when a copyright and license is added to all source files set(ament_cmake_copyright_FOUND TRUE) # the following line skips cpplint (only works in a git repo) # comment the line when this package is in a git repo and when # a copyright and license is added to all source files set(ament_cmake_cpplint_FOUND TRUE) ament_lint_auto_find_test_dependencies()endif()ament_package()
编译：colcon build --symlink-install
[ 50%] Building CXX object CMakeFiles/simple_node.dir/src/simple_node.cpp.o[100%] Linking CXX executable simple_node[100%] Built target simple_node
测试（执行）：ros2 run my_package simple_node
一个最简单的ROS2功能包完工。