官方wiki：http://wiki.ros.org/actionlib

1、说明

ROS中的action也是节点通信的一种方式，其和service-client的不同点在于，service-client是一问一答模式，而action则多了一个反馈机制，即服务端不间断给客户端反馈

api参考：https://docs.ros.org/en/api/actionlib/html/classactionlib_1_1SimpleActionClient.html

2、代码示例

跳过创建工作区和功能包步骤

2.1、定义数据结构

action定义的数据结构分成三个部分，中间用 --- 隔开，按照顺序如下：

2.1.1、goal

为了使action完成任务，引入一个目标概念，由客户端发送到服务端

2.1.4、result

结果由服务端发送给客户端，在完成 goal 之后，发送的任务结果

2.1.3、feedback

反馈为服务端发送到客户端，高度客户端，当前任务的进展

TestData.action

#请求的数据，一般由客户端发送给服务端
uint32 id
---
#请求结果，一般由服务端发送给客户端
uint32 total
---
#反馈的消息内容，一般由服务端不间断发送到客户端
float32 percent

.action 文件默认保存在 action 目录下

对于该文件，会生成7个消息类型，以便客户端和服务端通信，这些类型由 genaction.py 生成：

1. TestDataAction.msg
2. TestDataActionGoal.msg
3. TestDataActionResult.msg
4. TestDataActionFeedback.msg
5. TestDataGoal.msg
6. TestDataResult.msg
7. TestDataFeedback.msg

2.2、服务端

#include <ros/ros.h>
#include <test_action/TestDataAction.h>
#include <actionlib/server/simple_action_server.h>

typedef actionlib::SimpleActionServer<test_action::TestDataAction> Server;

void execute(const test_action::TestDataGoalConstPtr& goal, Server* server)
{
    ros::Rate rate(1);
    test_action::TestDataFeedback feedback;

    ROS_INFO("Dishwasher %d is working.", goal->id);

    for(int index = 1; index <= 10; index++)
    {
        feedback.percent = index * 10;
        server->publishFeedback(feedback);
        rate.sleep();
    }

    ROS_INFO("Dishwasher %d finish working.", goal->id);
    server->setSucceeded();
}

int main(int argc, char** argv)
{
    ros::init(argc, argv, "test_action_service");
    ros::NodeHandle handle;
    //构建一个action服务，第二个参数是服务的名称，客户端需要根据这个唯一的名称进行连接
    //最后一个参数表示是否构建完成之后就开始运行，一般应该设置为false，并在构建完成之后使用start()方法开始
    Server server(handle, "do_action", 
                  boost::bind(&execute, _1, &server), false);
    server.start();
    ros::spin();
    return 0;
}

2.3、客户端

#include <ros/ros.h>
#include <test_action/TestDataAction.h>
#include <actionlib/client/simple_action_client.h>

typedef actionlib::SimpleActionClient<test_action::TestDataAction> Client;

//完成调用回调
void doneCb(const actionlib::SimpleClientGoalState& state,
            const test_action::TestDataResultConstPtr& result)
{
    ROS_INFO("The dishes are now clean");
    ros::shutdown();
}

void activeCb()
{
    ROS_INFO("goal just went active");
}

//反馈
void feedbackCb(const test_action::TestDataFeedbackConstPtr& feedback)
{
    ROS_INFO("percent: %f", feedback->percent);
}

int main(int args, char** argv)
{
    ros::init(args, argv, "test_action_client");
    Client client("do_action", true);
    ROS_INFO("waiting for action server to start");
    client.waitForServer();
    ROS_INFO("action server started, sending goal");

    test_action::TestDataGoal goal;
    goal.id = 9;//填入goal
    //客户端发送目标，后三个是各个阶段的回调，分别在完成时、通信刚激活时和反馈过程中
    client.sendGoal(goal, &doneCb, &activeCb, &feedbackCb);
    ros::spin();

    return 0;
}

2.4、构建配置

CMakeLists.txt需要添加以下包依赖

find_package(catkin REQUIRED genmsg actionlib_msgs actionlib)
add_action_files(DIRECTORY action FILES DoDishes.action)
generate_messages(DEPENDENCIES actionlib_msgs)

其中，genmsg 和 actionlib_msgs 是构建 .action 文件的时候需要的依赖，actionlib 是编译的时候需要的依赖

packages.xml 配置

<buildtool_depend>catkin</buildtool_depend>
<buildtool_depend>genmsg</buildtool_depend>
<build_export_depend>actionlib_msgs</build_export_depend>
<build_depend>actionlib</build_depend>
<build_depend>actionlib_msgs</build_depend>
<exec_depend>actionlib</exec_depend>
<exec_depend>actionlib_msgs</exec_depend>

2.5、结果

服务端：

[ INFO] [1621921903.942496821]: Dishwasher 9 is working.
[ INFO] [1621921913.942535907]: Dishwasher 9 finish working.

客户端：

[ INFO] [1621921903.728245862]: waiting for action server to start
[ INFO] [1621921903.941538934]: action server started, sending goal
[ INFO] [1621921903.942692392]: goal just went active
[ INFO] [1621921903.943088999]: percent: 10.000000
[ INFO] [1621921904.942911217]: percent: 20.000000
[ INFO] [1621921905.942921653]: percent: 30.000000
[ INFO] [1621921906.942895095]: percent: 40.000000
[ INFO] [1621921907.942843906]: percent: 50.000000
[ INFO] [1621921908.942901935]: percent: 60.000000
[ INFO] [1621921909.942896131]: percent: 70.000000
[ INFO] [1621921910.942844776]: percent: 80.000000
[ INFO] [1621921911.942889215]: percent: 90.000000
[ INFO] [1621921912.942941318]: percent: 100.000000
[ INFO] [1621921913.943146759]: The dishes are now clean