ROS学习  ROS第一个简单例子

作者： Sam (甄峰)  sam_code@hotmail.com

ROS学习过程中，Sam准备学习的第一个例子是：从头建立一个catkin package, 并创建一个发布者(Publisher)和订阅者(Subscriber)。

1. catkin package的创建：
Sam在 catkin_ws/src/Test_Source目录下，运行：
$catkin_create_pkg Message_Source std_msgs roscpp
创建了Message_Source这个catkin Package. 它依赖于std_msgs, roscpp等Package.
（这里是有问题的，Package Name应该以小写字母为开头）
所以修改为：
$catkin_create_pkg messager std_msgs roscpp


可以看到如下结果：
在catkin_ws/src/Test_Source目录下，可以看到messager目录。
而messager目录内又包含：
CMakeLists.txt  include  package.xml  src
可以看到，它既包含CMakeLists.txt,  又包含package.xml.  所以，它正是一个catkin Package.

修改package.xml：
  exbot
 BSD


2. 创建一个Publisher Node.
在catkin_ws/src/Test_Source/Message_Source/src目录内，创建一个文件,talker_sam.cpp.

// %Tag(FULLTEXT)%
// %Tag(ROS_HEADER)%
#include "ros/ros.h"
// %EndTag(ROS_HEADER)%
// %Tag(MSG_HEADER)%
#include "std_msgs/String.h"
// %EndTag(MSG_HEADER)%

#include


int main(int argc, char **argv)
{
 
// %Tag(INIT)%
  ros::init(argc, argv, "talker");
// %EndTag(INIT)%

 
// %Tag(NODEHANDLE)%
  ros::NodeHandle n;
// %EndTag(NODEHANDLE)%

 
// %Tag(PUBLISHER)%
  ros::Publisher chatter_pub = n.advertise("chatter", 1000);
// %EndTag(PUBLISHER)%

// %Tag(LOOP_RATE)%
  ros::Rate loop_rate(10);
// %EndTag(LOOP_RATE)%

 
// %Tag(ROS_OK)%
  int count = 0;
  while (ros::ok())
  {
// %EndTag(ROS_OK)%
   
// %Tag(FILL_MESSAGE)%
    std_msgs::String msg;

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

// %Tag(ROSCONSOLE)%
    ROS_INFO("%s", msg.data.c_str());
// %EndTag(ROSCONSOLE)%

   
// %Tag(PUBLISH)%
    chatter_pub.publish(msg);
// %EndTag(PUBLISH)%

// %Tag(SPINONCE)%
    ros::spinOnce();
// %EndTag(SPINONCE)%

// %Tag(RATE_SLEEP)%
    loop_rate.sleep();
// %EndTag(RATE_SLEEP)%
    ++count;
  }


  return 0;
}
// %EndTag(FULLTEXT)%




3. 创建一个Subscriber:
在catkin_ws/src/Test_Source/Message_Source/src目录内，创建一个文件,listener_sam.cpp

// %Tag(CALLBACK)%
void chatterCallback(const std_msgs::String::ConstPtr& msg)
{
  ROS_INFO("I heard: [%s]", msg->data.c_str());
}
// %EndTag(CALLBACK)%

int main(int argc, char **argv)
{
 
  ros::init(argc, argv, "listener");

 
  ros::NodeHandle n;

 
// %Tag(SUBSCRIBER)%
  ros::Subscriber sub = n.subscribe("chatter", 1000, chatterCallback);
// %EndTag(SUBSCRIBER)%

 
// %Tag(SPIN)%
  ros::spin();
// %EndTag(SPIN)%

  return 0;
}
// %EndTag(FULLTEXT)%

owing disclaimer.
 *   * Redistributions in binary form must reproduce the above copyright
 *     notice, this list of conditions and the following disclaimer in the
 *     documentation and/or other materials provided with the distribution.
 *   * Neither the names of Stanford University or Willow Garage, Inc. nor the names of its
 *     contributors may be used to endorse or promote products derived from
 *     this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */

// %Tag(FULLTEXT)%
#include "ros/ros.h"
#include "std_msgs/String.h"


// %Tag(CALLBACK)%
void chatterCallback(const std_msgs::String::ConstPtr& msg)
{
  ROS_INFO("I heard: [%s]", msg->data.c_str());
}
// %EndTag(CALLBACK)%

int main(int argc, char **argv)
{
 
  ros::init(argc, argv, "listener");

 
  ros::NodeHandle n;

 
// %Tag(SUBSCRIBER)%
  ros::Subscriber sub = n.subscribe("chatter", 1000, chatterCallback);
// %EndTag(SUBSCRIBER)%

 
// %Tag(SPIN)%
  ros::spin();
// %EndTag(SPIN)%

  return 0;
}
// %EndTag(FULLTEXT)%


4. 修改CMakeLists.txt
把talker_sam.cpp, listener.cpp添加入Makefile.
add_executable(talker_sam src/talker_sam.cpp)
target_link_libraries(talker_sam ${catkin_LIBRARIES})

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


5. 运行与验证：
5.1：首先运行所有程序：
$roscore
$rosrun messager takler_sam
$rosrun messager listener_sam

可以看到，终端上各自打印出各类信息。

5.2：验证：
$rosrun rqt_graph rqt_graph
/talker---->/listener
Topic名为：/chatter

5.3：查看Topic内容：
前面可以看到Topic的名子为：/chatter
$rostopic echo /chatter
可以看到Topic内容。

$rostopic type /chatter
可以看到Topic Message内容。