ROS_hydro_catkin建立标准程序包_helloworld.h+helloworld.cpp+helloworldnode.cpp

1.创建标准catkin工作空间

mkdir mycatkin

cd mycatkin

mkdir build devel src
catkin_make

source devel/setup.bash

2.创建一个catkin程序包

mkdir src/modular_lib_pkg

Add bare-bones Catkin CMakeLists.txt and package.xml files to make yourdirectory a valid package:

src/modular_lib_pkg/CMakeLists.txt

# Declare the version of the CMake API for forward-compatibilitycmake_minimum_required(VERSION 2.8)# Declare the name of the CMake Projectproject(modular_lib_pkg)# Find Catkinfind_package(catkin REQUIRED)# Declare this project as a catkin packagecatkin_package()

src/modular_lib_pkg/package.xml

<package>  <!-- Package Metadata -->  <name>modular_lib_pkg</name>  <maintainer email="[e-mail]">Your Name</maintainer>  <description>    A ROS tutorial on modularity.  </description>  <version>0.0.0</version>  <license>BSD</license>  <!-- Required by Catkin -->  <buildtool_depend>catkin</buildtool_depend></package>

3.Separating Functionality into a Library

Create the Library Code

The header with the declaration of our say_hello() function is as follows:

modular_lib_pkg/include/modular_lib_pkg/hello_world.h

// Inclusion guard to prevent this header from being included multiple times#ifndef __MODULAR_LIB_PKG_HELLO_WORLD_H#define __MODULAR_LIB_PKG_HELLO_WORLD_H//! Broadcast a hello-world message over ROS_INFOvoid say_hello();#endif

The source file with the definition of say_hello() is as follows:

modular_lib_pkg/src/hello_world.cpp

// Include the ROS C++ APIs#include <ros/ros.h>void say_hello() {  ROS_INFO_STREAM("Hello, world!");}

Now that we’ve written the code for the library, we can add a rule to theCMakeLists.txt file to actually build it. Note that just like in the ROS C++hello-world tutorial⁹, we need to add a dependency onroscpp in order to use ROS. This is just like adding an executable with theadd_executable() CMake command: instead, we useadd_library():

src/modular_lib_pkg/CMakeLists.txt

# Declare the version of the CMake API for forward-compatibilitycmake_minimum_required(VERSION 2.8)# Declare the name of the CMake Projectproject(modular_lib_pkg)# Find and get all the information about the roscpp packagefind_package(roscpp REQUIRED)# Find Catkinfind_package(catkin REQUIRED)# Declare this project as a catkin packagecatkin_package()# Add the headers from roscppinclude_directories(${roscpp_INCLUDE_DIRS})# Define a library target called hello_worldadd_library(hello_world src/hello_world.cpp)target_link_libraries(hello_world ${roscpp_LIBRARIES})

Also, now that we’re using the roscpp package, we need to list itas a build- and run-dependency of our package:

src/modular_lib_pkg/package.xml

<package>  <!-- Package Metadata -->  <name>modular_lib_pkg</name>  <maintainer email="[e-mail]">Your Name</maintainer>  <description>    A ROS tutorial on modularity.  </description>  <version>0.0.0</version>  <license>BSD</license>  <!-- Required by Catkin -->  <buildtool_depend>catkin</buildtool_depend>  <!-- Package Dependencies -->  <build_depend>roscpp</build_depend>  <run_depend>roscpp</run_depend></package>

cd mycatkin

catkin_make

4.建立节点

modular_lib_pkg/src/hello_world_node.cpp

// Include the ROS C++ APIs#include <ros/ros.h>// Include the declaration of our library function#include <modular_lib_pkg/hello_world.h>// Standard C++ entry pointint main(int argc, char** argv) {  // Initialize ROS  ros::init(argc, argv, "hello_world_node");  ros::NodeHandle nh;  // Call our library function  say_hello();  // Wait for SIGINT/Ctrl-C  ros::spin();  return 0;}

To build this node, just add an appropriate add_executable() call to thebottom of the package’sCMakeLists.txt:

add_executable(hello_world_node src/hello_world_node.cpp)target_link_libraries(hello_world_node ${roscpp_LIBRARIES})

5.编译节点

At this point, you can try to build hello_world_node with catkin_make, but youwill see the following error:

[100%] Building CXX object modular_lib_pkg/CMakeFiles/hello_world_node.dir/src/hello_world_node.cpp.o/tmp/src/modular_lib_pkg/src/hello_world_node.cpp:5:42: fatal error: modular_lib_pkg/hello_world.h: No such file or directorycompilation terminated.

The compiler is complaining about modular_lib_pkg/hello_world.h notexisting, but weknow it exists! The problem isn’t that the file doesn’texist, but rather that we haven’t told the compiler where to look for it.

In the same way that we added the header search paths for roscpp, we alsoneed to add our own local include directory where we put our own headers. To doso, just add the relative path tosrc/modular_lib_pkg/include to theexistinginclude_directories() command inCMakeLists.txt:

include_directories(include ${roscpp_INCLUDE_DIRS)

Building the Node (and getting a linker error)

At this point, you can try to build hello_world_node with catkin_makeagain, but you will see another error:

[100%] Building CXX object modular_lib_pkg/CMakeFiles/hello_world_node.dir/src/hello_world_node.cpp.oLinking CXX executable /tmp/foo/devel/lib/modular_lib_pkg/hello_world_nodeCMakeFiles/hello_world_node.dir/src/hello_world_node.cpp.o:hello_world_node.cpp:function main: error: undefined reference to 'say_hello()'collect2: ld returned 1 exit status

This time, hello_world_node.cpp is compiled successfully, but thelinkerreports an error that thesay_hello() function is undefined. The declarationwas found in thehello_world.h header file, otherwise it wouldn’t havecompiled, still the definition fromhello_world.cpp was missing.

In order to resolve this, in addition to linking against ${roscpp_LIBRARIES},we also linkhello_world_node against thehello_world target so that itssymbols are defined for the linker. This is done by addinghello_world to theexistingtarget_link_libraries() command like the following:

target_link_libraries(hello_world_node ${roscpp_LIBRARIES} hello_world)

The following CMakeLists.txt file contains both this and the previousmodifications:

src/modular_lib_pkg/CMakeLists.txt

# Declare the version of the CMake API for forward-compatibilitycmake_minimum_required(VERSION 2.8)# Declare the name of the CMake Projectproject(modular_lib_pkg)# Find and get all the information about the roscpp packagefind_package(roscpp REQUIRED)# Find Catkinfind_package(catkin REQUIRED)# Declare this project as a catkin packagecatkin_package()# Add the local headers and the headers from roscppinclude_directories(include ${roscpp_INCLUDE_DIRS})# Define a library target called hello_worldadd_library(hello_world src/hello_world.cpp)target_link_libraries(hello_world ${roscpp_LIBRARIES})# Define an executable target called hello_world_nodeadd_executable(hello_world_node src/hello_world_node.cpp)target_link_libraries(hello_world_node ${roscpp_LIBRARIES} hello_world)

catkin_make

rosrun modular_lib_pkg hello_world_node

问题：

[rosrun] Couldn't find executable named hello_world_node below /home/hsn/mycatkin/src/modular_lib_pkg
解决：

cd mycatkin

source devel/setup.bash

其他问题：

roscore

或者sudo apt-get update

参考：http://jbohren.com/articles/modular-ros-packages/