目标:在ROS2中学习更多的实现自定义接口
背景
在指定的接口包中声明接口,有时在一个包中声明、创建、使用所有接口很方便。
本教程关注msg接口类型,但是步骤对于其他所有接口类型适用。
任务
1、创建一个包
ros2 pkg create --build-type ament_cmake more_interfaces
mkdir more_interfaces/msg
2、创建一个msg文件
AddressBook.msg
uint8 PHONE_TYPE_HOME=0
uint8 PHONE_TYPE_WORK=1
uint8 PHONE_TYPE_MOBILE=2
string first_name
string last_name
string phone_number
uint8 phone_type
See About ROS 2 interfaces for more ways you can customize interfaces.
2.1 编译msg文件
package.xml
<buildtool_depend>rosidl_default_generators</buildtool_depend>
<exec_depend>rosidl_default_runtime</exec_depend>
<member_of_group>rosidl_interface_packages</member_of_group>
CMakeLists.txt
cmake_minimum_required(VERSION 3.8)
project(more_interfaces)
if(CMAKE_COMPILER_IS_GNUCXX OR CMAKE_CXX_COMPILER_ID MATCHES "Clang")
add_compile_options(-Wall -Wextra -Wpedantic)
endif()
# find dependencies
find_package(ament_cmake REQUIRED)
find_package(rosidl_default_generators REQUIRED)
# uncomment the following section in order to fill in
# further dependencies manually.
# find_package(<dependency> REQUIRED)
set(msg_files
"msg/AddressBook.msg"
)
rosidl_generate_interfaces(${PROJECT_NAME}
${msg_files}
)
ament_export_dependencies(rosidl_default_runtime)
if(BUILD_TESTING)
find_package(ament_lint_auto REQUIRED)
# the following line skips the linter which checks for copyrights
# comment the line when a copyright and license is added to all source files
set(ament_cmake_copyright_FOUND TRUE)
# the following line skips cpplint (only works in a git repo)
# comment the line when this package is in a git repo and when
# a copyright and license is added to all source files
set(ament_cmake_cpplint_FOUND TRUE)
ament_lint_auto_find_test_dependencies()
endif()
ament_package()
2.2 设置更多的接口
在CMakeLists.txt中设置
set(msg_files
"msg/Message1.msg"
"msg/Message2.msg"
# etc
)
set(srv_files
"srv/Service1.srv"
"srv/Service2.srv"
# etc
)
生成所有的消息
rosidl_generate_interfaces(${PROJECT_NAME}
${msg_files}
${srv_files}
)
3、使用来自相同包的接口
在more_interfaces/src下创建publish_address_book.cpp
#include <chrono>
#include <memory>
#include "rclcpp/rclcpp.hpp"
#include "more_interfaces/msg/address_book.hpp"
using namespace std::chrono_literals;
class AddressBookPublisher : public rclcpp::Node
{
public:
AddressBookPublisher()
: Node("address_book_publisher")
{
address_book_publisher_ =
this->create_publisher<more_interfaces::msg::AddressBook>("address_book", 10);
auto publish_msg = [this]() -> void {
auto message = more_interfaces::msg::AddressBook();
message.first_name = "John";
message.last_name = "Doe";
message.phone_number = "1234567890";
message.phone_type = message.PHONE_TYPE_MOBILE;
std::cout << "Publishing Contact\nFirst:" << message.first_name <<
" Last:" << message.last_name << std::endl;
this->address_book_publisher_->publish(message);
};
timer_ = this->create_wall_timer(1s, publish_msg);
}
private:
rclcpp::Publisher<more_interfaces::msg::AddressBook>::SharedPtr address_book_publisher_;
rclcpp::TimerBase::SharedPtr timer_;
};
int main(int argc, char * argv[])
{
rclcpp::init(argc, argv);
rclcpp::spin(std::make_shared<AddressBookPublisher>());
rclcpp::shutdown();
return 0;
}
在CMakeLists.txt中添加如下
find_package(rclcpp REQUIRED)
add_executable(publish_address_book src/publish_address_book.cpp)
ament_target_dependencies(publish_address_book rclcpp)
install(TARGETS
publish_address_book
DESTINATION lib/${PROJECT_NAME})
3.1与自定义接口类型链接
为了使用本包生成的消息,需要再CMakeLists.txt中添加如下
rosidl_get_typesupport_target(cpp_typesupport_target
${PROJECT_NAME} rosidl_typesupport_cpp)
target_link_libraries(publish_address_book "${cpp_typesupport_target}")
您可能已经注意到,当使用的接口来自独立构建的不同包时,没有必要执行此步骤。只有当您希望在与定义接口的包相同的包中使用接口时,才需要此CMake代码。
4、编译并运行
colcon build --packages-up-to more_interfaces
source install/local_setup.bash
ros2 run more_interfaces publish_address_book
查看消息内容
source install/setup.bash
ros2 topic echo /address_book
5、使用已经存在的接口定义
注意
可以在一个新的接口定义中使用已经存在的接口定义。例如,有一个消息的名字叫做Contact.msg,其属于包rosidl_tutorials_msgs。可以在自己的包中定义如下的数组
rosidl_tutorial_msgs/Contact[] address_book
为了生成依赖的消息Contack.msg,需要再package.xml中添加对应的包rosidl_tutorial_msgs
如下
<build_depend>rosidl_tutorials_msgs</build_depend>
<exec_depend>rosidl_tutorials_msgs</exec_depend>
在CMakeLists.txt中添加如下
find_package(rosidl_tutorials_msgs REQUIRED)
rosidl_generate_interfaces(${PROJECT_NAME}
${msg_files}
DEPENDENCIES rosidl_tutorials_msgs
)
在cpp文件中需要添加头文件#include "rosidl_tutorials_msgs/msg/contact.hpp"
以及如下的修改
auto publish_msg = [this]() -> void {
auto msg = std::make_shared<more_interfaces::msg::AddressBook>();
{
rosidl_tutorials_msgs::msg::Contact contact;
contact.first_name = "John";
contact.last_name = "Doe";
contact.phone_number = "1234567890";
contact.phone_type = message.PHONE_TYPE_MOBILE;
msg->address_book.push_back(contact);
}
{
rosidl_tutorials_msgs::msg::Contact contact;
contact.first_name = "Jane";
contact.last_name = "Doe";
contact.phone_number = "4254242424";
contact.phone_type = message.PHONE_TYPE_HOME;
msg->address_book.push_back(contact);
}
std::cout << "Publishing address book:" << std::endl;
for (auto contact : msg->address_book) {
std::cout << "First:" << contact.first_name << " Last:" << contact.last_name <<
std::endl;
}
address_book_publisher_->publish(*msg);
};
总结
在本教程中,您尝试了不同的字段类型来定义接口,然后在使用接口的同一个包中构建了一个接口。您还学习了如何使用其他接口作为字段类型,以及使用该功能所需的package.xml、CMakeLists.txt和#include语句。