学习ROS（一）——体验ROS，第一个简单的示例

本文建立在已经安装好ROS环境的情况下，下面编写第一个ROS订阅发布程序。

1.首先创建项目目录：

mkdir -p ~/catkin_ws/src

进入src文件夹

cd ~/catkin_ws/src

项目目录名为：catkin_ws

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2.现在使用catkin_create_pkg命令来创建一个名为'beginner_tutorials'的新程序包，这个程序包依赖于std_msgs、roscpp和rospy：

catkin_create_pkg beginner_tutorials std_msgs rospy roscpp

这将会创建一个名为beginner_tutorials的文件夹，这个文件夹里面包含一个package.xml文件和一个CMakeLists.txt文件，这两个文件都已经自动包含了部分你在执行catkin_create_pkg命令时提供的信息。

 

3.在 beginner_tutorials package 路径下创建一个src文件夹：

在 beginner_tutorials package 路径下创建一个src文件夹：

mkdir -p ~/catkin_ws/src/beginner_tutorials/src

这个文件夹将会用来放置 beginner_tutorials package 的所有源代码。

此时，beginner_tutorials文件夹内包含类似如下：

 

在 beginner_tutorials package 里创建 src/talker.cpp 文件，并将如下代码粘贴到文件内：

#include "ros/ros.h"
#include "std_msgs/String.h"

#include <sstream>

/**
 * This tutorial demonstrates simple sending of messages over the ROS system.
 */
int main(int argc, char **argv)
{
  /**
   * The ros::init() function needs to see argc and argv so that it can perform
   * any ROS arguments and name remapping that were provided at the command line. For programmatic
   * remappings you can use a different version of init() which takes remappings
   * directly, but for most command-line programs, passing argc and argv is the easiest
   * way to do it.  The third argument to init() is the name of the node.
   *
   * You must call one of the versions of ros::init() before using any other
   * part of the ROS system.
   */
  ros::init(argc, argv, "talker");

  /**
   * NodeHandle is the main access point to communications with the ROS system.
   * The first NodeHandle constructed will fully initialize this node, and the last
   * NodeHandle destructed will close down the node.
   */
  ros::NodeHandle n;

  /**
   * The advertise() function is how you tell ROS that you want to
   * publish on a given topic name. This invokes a call to the ROS
   * master node, which keeps a registry of who is publishing and who
   * is subscribing. After this advertise() call is made, the master
   * node will notify anyone who is trying to subscribe to this topic name,
   * and they will in turn negotiate a peer-to-peer connection with this
   * node.  advertise() returns a Publisher object which allows you to
   * publish messages on that topic through a call to publish().  Once
   * all copies of the returned Publisher object are destroyed, the topic
   * will be automatically unadvertised.
   *
   * The second parameter to advertise() is the size of the message queue
   * used for publishing messages.  If messages are published more quickly
   * than we can send them, the number here specifies how many messages to
   * buffer up before throwing some away.
   */
  ros::Publisher chatter_pub = n.advertise<std_msgs::String>("chatter", 1000);

  ros::Rate loop_rate(10);

  /**
   * A count of how many messages we have sent. This is used to create
   * a unique string for each message.
   */
  int count = 0;
  while (ros::ok())
  {
    /**
     * This is a message object. You stuff it with data, and then publish it.
     */
    std_msgs::String msg;

    std::stringstream ss;
    ss << "hello world " << count;
    msg.data = ss.str();

    ROS_INFO("%s", msg.data.c_str());

    /**
     * The publish() function is how you send messages. The parameter
     * is the message object. The type of this object must agree with the type
     * given as a template parameter to the advertise<>() call, as was done
     * in the constructor above.
     */
    chatter_pub.publish(msg);

    ros::spinOnce();

    loop_rate.sleep();
    ++count;
  }


  return 0;
}

在 beginner_tutorials package 目录下创建 src/listener.cpp 文件，并粘贴如下代码：

#include "ros/ros.h"
#include "std_msgs/String.h"

/**
 * This tutorial demonstrates simple receipt of messages over the ROS system.
 */
void chatterCallback(const std_msgs::String::ConstPtr& msg)
{
  ROS_INFO("I heard: [%s]", msg->data.c_str());
}

int main(int argc, char **argv)
{
  /**
   * The ros::init() function needs to see argc and argv so that it can perform
   * any ROS arguments and name remapping that were provided at the command line. For programmatic
   * remappings you can use a different version of init() which takes remappings
   * directly, but for most command-line programs, passing argc and argv is the easiest
   * way to do it.  The third argument to init() is the name of the node.
   *
   * You must call one of the versions of ros::init() before using any other
   * part of the ROS system.
   */
  ros::init(argc, argv, "listener");

  /**
   * NodeHandle is the main access point to communications with the ROS system.
   * The first NodeHandle constructed will fully initialize this node, and the last
   * NodeHandle destructed will close down the node.
   */
  ros::NodeHandle n;

  /**
   * The subscribe() call is how you tell ROS that you want to receive messages
   * on a given topic.  This invokes a call to the ROS
   * master node, which keeps a registry of who is publishing and who
   * is subscribing.  Messages are passed to a callback function, here
   * called chatterCallback.  subscribe() returns a Subscriber object that you
   * must hold on to until you want to unsubscribe.  When all copies of the Subscriber
   * object go out of scope, this callback will automatically be unsubscribed from
   * this topic.
   *
   * The second parameter to the subscribe() function is the size of the message
   * queue.  If messages are arriving faster than they are being processed, this
   * is the number of messages that will be buffered up before beginning to throw
   * away the oldest ones.
   */
  ros::Subscriber sub = n.subscribe("chatter", 1000, chatterCallback);

  /**
   * ros::spin() will enter a loop, pumping callbacks.  With this version, all
   * callbacks will be called from within this thread (the main one).  ros::spin()
   * will exit when Ctrl-C is pressed, or the node is shutdown by the master.
   */
  ros::spin();

  return 0;
}

 

4. 打开CMakeLists.txt（类似下图目录下的CMakeLists.txt）

在 CMakeLists.txt 文件末尾加入几条语句:

include_directories(include ${catkin_INCLUDE_DIRS})

add_executable(talker src/talker.cpp)
target_link_libraries(talker ${catkin_LIBRARIES})

add_executable(listener src/listener.cpp)
target_link_libraries(listener ${catkin_LIBRARIES})

 

类似如下：

 

5.现在运行 catkin_make：

回到项目目录，cd ~/catkin_make,然后执行

catkin_make

 

看到类似下面的图就说明编译成功

 

项目目录（catkin_ws）中多出两个目录

6.确保roscore可用，打开新的终端，并运行：

roscore

 

7.source ～/项目所在目录/devel/setup.bash

确保你在调用catkin_make后，在运行你自己的程序前，已经source了catkin工作空间下的setup.sh文件：
也就是在执行rosrun命令之前之前必须source一下

source ~/项目所在目录/devel/setup.bash

　　

 

8.运行发布器

然后打开另一个终端

记得先执行

source ~/catkin_ws/devel/setup.bash

然后再执行：

rosrun beginnerK_tutorials listener 

总之，如果需要rosrun另一个程序，先新打开的窗口，需要source一下

 

以上就是ROS中订阅发布模式的简单使用

参考：

http://wiki.ros.org/cn/ROS/Tutorials/ 

https://www.cnblogs.com/liu-fa/p/5779206.html

https://blog.csdn.net/xiao__run/article/details/84675245

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