04-actionlib入门-新建action server

新建 action messages

在新建action之前，有必要先定义好什么是目标goal，结果result，反馈信息feedback。action信息有 .action 文件自动生成，更多action文件的信息可见下面的文件actionlib. 文件定义了goal, result, feedback主题的类型与格式，在目录中新建如下文件learning_actionlib/action/Fibonacci.action，内容复制如下的代码：

#goal definition
int32 order
---
#result definition
int32[] sequence
---
#feedback
int32[] sequence

为了自动生成一系列message文件，需要在CMakeLists.txt中变更如下的语句：
.
在 CMakeLists.txt中find_package行更改为下面内容：

find_package(catkin REQUIRED COMPONENTS actionlib_msgs)

• (actionlib_msgs包括了message_generation，因此不需要再列出message_generation组件).

增加使用的action文件：

add_action_files( DIRECTORY action FILES fac.action)

添加actionlib_msgs到 generate_messages：
:

generate_messages( DEPENDENCIES actionlib_msgs std_msgs

添加actionlib_msgs到catkin_package：

catkin_package( CATKIN_DEPENDS actionlib_msgs)

• (catkin_packag只能添加CATKIN_DEPEND到actionlib_msgs

接下来可以开始自动生成msg：

$ cd ../.. # 到工作空间
$ catkin_make
$ ls devel/share/learning_actionlib/msg/

facActionFeedback.msg facAction.msg facFeedback.msgfacResult.msg facActionGoal.msg facActionResult.msg facGoal.msg

$ ls devel/include/learning_actionlib/

facActionFeedback.h facAction.h facFeedback.h facResult.hfacActionGoal.h facActionResult.h facGoal.h

可以使用actionlib_msgs包中的genaction.py脚本手动生成msg。

写一个简单的服务端

代码阳历在 actionlib_tutorials 软件包中，可以先阅读 actionlib 软件包.

代码

代码在actionlib_tutorials/simple_action_servers/fac_server.py中：
#! /usr/bin/env python

import roslib; roslib.load_manifest('actionlib_tutorials')
import rospy

import actionlib

import actionlib_tutorials.msg

class FibonacciAction(object):
  # create messages that are used to publish feedback/result
  _feedback = actionlib_tutorials.msg.FibonacciFeedback()
  _result   = actionlib_tutorials.msg.FibonacciResult()

  def __init__(self, name):
    self._action_name = name
    self._as = actionlib.SimpleActionServer(self._action_name, actionlib_tutorials.msg.FibonacciAction, execute_cb=self.execute_cb, auto_start = False)
    self._as.start()
    
  def execute_cb(self, goal):
    # helper variables
    r = rospy.Rate(1)
    success = True
    
    # append the seeds for the fibonacci sequence
    self._feedback.sequence = []
    self._feedback.sequence.append(0)
    self._feedback.sequence.append(1)
    
    # publish info to the console for the user
    rospy.loginfo('%s: Executing, creating fibonacci sequence of order %i with seeds %i, %i' % (self._action_name, goal.order, self._feedback.sequence[0], self._feedback.sequence[1]))
    
    # start executing the action
    for i in xrange(1, goal.order):
      # check that preempt has not been requested by the client
      if self._as.is_preempt_requested():
        rospy.loginfo('%s: Preempted' % self._action_name)
        self._as.set_preempted()
        success = False
        break
      self._feedback.sequence.append(self._feedback.sequence[i] + self._feedback.sequence[i-1])
      # publish the feedback
      self._as.publish_feedback(self._feedback)
      # this step is not necessary, the sequence is computed at 1 Hz for demonstration purposes
      r.sleep()
      
    if success:
      self._result.sequence = self._feedback.sequence
      rospy.loginfo('%s: Succeeded' % self._action_name)
      self._as.set_succeeded(self._result)
      
if __name__ == '__main__':
  rospy.init_node('fibonacci')
  FibonacciAction(rospy.get_name())
  rospy.spin()

运行服务端程序

python fibonacci_server.py