Hello,
I'm having few SMACH states in different files and would like to use TF in some of them. There will be probably even some concurrent states so, I created helper class tf_utils (helper_methods.py) with TF listener protected by mutex. It's initialized like this:
_tfl = None
def get_tfl():
return _tfl
def init_tfl():
global _tfl
if _tfl is None:
_tfl = tf_utils()
Class tf_utils looks like this:
class tf_utils():
def __init__(self,timeout=None):
if timeout is None:
timeout = rospy.Duration(5)
self.timeout = timeout
self.tfl = TransformListener()
self.mutex = threading.Lock()
def waitForTransform(self,f1,f2,time):
ret = True
self.mutex.acquire()
try:
self.tfl.waitForTransform(f1,f2,time,self.timeout)
except tf.Exception:
ret = False
self.mutex.release()
return ret
etc...
In main file, I initialize node (rospy.init_node) and tf_utils (helper_methods.init_tfl()). Then for instance frameExists method works fine while with waitForTransform I'm getting this:
terminate called after throwing an instance of 'ros::TimeNotInitializedException' what(): Cannot use ros::Time::now() before the first NodeHandle has been created or ros::start() has been called. If this is a standalone app or test that just uses ros::Time and does not communicate over ROS, you may also call ros::Time::init()
Situation is same for both wall time or simulated time.
What's wrong? Or is there any other approach how to use one transform listener in more python modules / SMACH states?
UPDATE:
This is how I initialize my stuff. First I initialize rospy and then (in main) my tf listener.
if __name__ == '__main__':
rospy.init_node('rt_decision_making')
try:
main()
except rospy.ROSInterruptException:
print "program interrupted before completion"
and...
def main(): helper_methods.init_tfl() tfl = helper_methods.get_tfl()
UPDATE2:
I ended up with the most simple python script:
#!/usr/bin/env python
import roslib; roslib.load_manifest('rt_decision_making')
import rospy
import tf
from tf import TransformListener
def main():
rospy.init_node('rt_decision_making')
rospy.sleep(2)
tfl = TransformListener()
rospy.sleep(2)
tfl.waitForTransform("base_link", "velodyne", rospy.Time.now(), rospy.Duration(1))
if __name__ == '__main__':
try:
main()
except rospy.ROSInterruptException:
print "program interrupted before completion"
...which works in Groovy but not in Hydro which I'm currently working with.
Originally posted by ZdenekM on ROS Answers with karma: 704 on 2013-07-31
Post score: 0
