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Client Library
This concept concept and our understanding of the API is very similar. Offer ROS is essentially a programming library. For example: the establishment node, announced that invoke the service. It encapsulates the underlying operational processes, help us to write code to call.
The client library has several versions: roscpp, rospy, roslisp
The top two talk about the roscpp, this lecture will be mentioned rospy. rospy interfaces including the Node, Topic, Service, Parameter, Time categories.
rospy
rospy-Node-related
Function
init_node (name) # Registration and initialize node
import rospy
rospy.init_node('my_node') # 没有返回值
MasterProxy
- get_master () # get a handle master of
bool
- is_shutdown () # Returns whether closed
- on_shutdown (fn) # call the function fn when the node is closed
str
- get_node_uri () # returns the node URI
- get_name () # returns the full name of this node
- get_namespace () # Returns the namespace of the current node
rospy-Topic related
Function
[[str1, str2]] get_published_topics () # returns all topic names are being released (str1) and type (str2)
Message
-
wait_for_message (topic, topic_type, time_out = None) # wait for the specified topic of a msg
-
spin () # trigger the topic of service or treatment, will be blocked until the close
Publisher class
- __init __ (self, name, data_class, queue_size = None) # Constructor
- publish (self, msg) # member functions to post a message
- unregister (self) # member function to stop publishing the
case:
pub = rospy.Publisher('topic_name','topic_type',queue_size=None) #size=None相当于同步通信，大于零会为异步通信
pub.publish(msg)
Subscriber class
- __init __ (self, name, data_class, call_back = None, queue_size = None) # Constructor
- unregister (self) # member functions unsubscribe
rospy-Service-related
function
wait_for_service (service, timeout = None) # blocked until the service is available
Service category -> server-related
_init_ (self, name, service_class, handler) # constructor service
shutdown (self) # member functions shut down service
handler case:
def handler(req):
pass
return res #只传入请求，只传出响应
ServiceProxy class > client related -
requestor __init __ (self, name, service_class ) # constructor and services
Response
- call (self, * args, ** kwds) # call service
- __call __ (self, * args, ** kwds) # call service
client = ServiceProxy(...) //构造函数
client.call(req)
#或者
resp = client(req)
rospy-Param-related
function
XmlRpcLegalValue
- get_param (param_name, default = _unspecified) # get the value of the parameter
[str]
- get_param_names () # Get the name of the parameter
- set_param (param_name, param_value) # set the value of the parameter
- delete_param (param_name) # delete parameters
bool
- has_param (param_name) # parameter exists on the server parameters
str
- search_param () # search parameters
rospy-Time-related
Class Time -> means time
__init __ (self, secs = 0 , nsecs = 0) # Constructor
Time now () # static method returns the current time Time object
case:
rospy.Time(secs = 1, nsecs = 0)
# or
rospy.Time.now()
Duration class -> means a period of time
__init __ (self, secs = 0 , nsecs = 0) # constructor second and nanosecond
Note : subtraction operation time, the results may vary in time, not the time and two addition and subtraction.
function
Time
- get_rostime () # Time current target time
float
- get_time () # returns the current time, it returns a float in seconds
- sleep (duration) # suspend execution
Rate class
__init __ (self, frequency) # constructor
sleep (self) # hangs once considered rate.sleep () time
Time
- remaining (self) # member functions remaining sleep time
Please indicate the source.
This paper summarizes the Chinese University of MOOC "Android OS Getting Started"
link: Link .
Pictures from the video capture program
