ROS3—创建包

1. 创建一个ROS包

利用roscreate-pkg和catkin来创建新包，用rospack来列出包的依赖。

2. 一个catkin包的组成

一个catkin包必须有：
- 一个catkin顺从包package.xml提供包的元信息
- 一个使用catkin的CMakeLists.txt
- 在每个文件夹中只有一个包

3.在catkin工作空间的包

workspace_folder/        -- WORKSPACE
    src/                 -- SOURCE SPACE
        CMakeLists.txt   -- 'Toplevel' CMake file. provided by catkin
        package_1/
            CMakeLists.txt    -- CMakeLists.txt file for package_1
            package.xml       -- Package manifest for package_1
        ...
        package_n/
            CMakeLists.txt    -- CMakeLists.txt file for package_n
            package.xml       -- Package manifest for package_n

4.创建一个catkin包

cd ~/catkin_ws/src
catkin_create_pkg <package_name> [depend1] [depend2] [depend3]

先转到catkin工作空间的source空间目录，再利用catkin_create_pkg创建新包。

5.建立catkin工作空间和运行setup文件

cd ~/catkin_ws
catkin_make
. ~/catkin_ws/devel/setup.bash

上面的代码会创建catkin工作空间的，在devel子目录/opt/ros/$ROSDISTRO_NAME创建类似的结构；并将工作空间添加到ROS环境中。

6.包依赖

6.1直接依赖

rospack depends1 <package_name>
roscd <package_name>
cat package.xml

使用catkin_create_pkg时会提供一些依赖包，这些一级依赖包可通过rospack查看。而这些依赖也存储在package.xml文件中。

6.2非直接依赖

rospack depends <package_name>

许多依赖包也会有自己的依赖包。而上述命令可以递归地列出内嵌的依赖。

7.定制你的包

7.1定制文件package.xml

描述标签

<description>The beginner_tutorial package</description>

更新描述标签，可以将描述换成任何你希望的。
然后是维护者标签。

<!-- One maintainer tag required, multiple allowed, one person per tag --> 
<!-- Example:  -->
<!-- <maintainer email="jane.doe@example.com">Jane Doe</maintainer> -->
<maintainer email="user@todo.todo">user</maintainer>

然后是许可标签

<!-- One license tag required, multiple allowed, one license per tag -->
<!-- Commonly used license strings: -->
<!--   BSD, MIT, Boost Software License, GPLv2, GPLv3, LGPLv2.1, LGPLv3 -->
<license>TODO</license>

接下来是依赖标签。依赖包被分为build_depend，buildtool_depend，run_depend和test_depend。

<!-- The *_depend tags are used to specify dependencies -->
<!-- Dependencies can be catkin packages or system dependencies -->
<!-- Examples: -->
<!-- Use build_depend for packages you need at compile time: -->
<!--   <build_depend>genmsg</build_depend> -->
<!-- Use buildtool_depend for build tool packages: -->
<!--   <buildtool_depend>catkin</buildtool_depend> -->
<!-- Use run_depend for packages you need at runtime: -->
<!--   <run_depend>python-yaml</run_depend> -->
<!-- Use test_depend for packages you need only for testing: -->
<!--   <test_depend>gtest</test_depend> -->
<buildtool_depend>catkin</buildtool_depend>
<build_depend>roscpp</build_depend>
<build_depend>rospy</build_depend>
<build_depend>std_msgs</build_depend>

最终的package.xml文件为：

<?xml version="1.0"?>
<package>
  <name>beginner_tutorials</name>
  <version>0.1.0</version>
  <description>The beginner_tutorials package</description>

  <maintainer email="you@yourdomain.tld">Your Name</maintainer>
  <license>BSD</license>
  <url type="website">http://wiki.ros.org/beginner_tutorials</url>
  <author email="you@yourdomain.tld">Jane Doe</author>

  <buildtool_depend>catkin</buildtool_depend>

  <build_depend>roscpp</build_depend>
  <build_depend>rospy</build_depend>
  <build_depend>std_msgs</build_depend>

  <run_depend>roscpp</run_depend>
  <run_depend>rospy</run_depend>
  <run_depend>std_msgs</run_depend>

</package>

7.2定制CMakeLists.txt文件

详见后面的内容。