I'm using ROS2 humble under Windows. I have a very simple PyQt based publisher and subscriber:
Publisher:
import rclpy
from rclpy.node import Node
from rclpy.executors import MultiThreadedExecutor
from sensor_msgs.msg import ChannelFloat32
from PyQt5.QtWidgets import QApplication, QWidget, QPushButton, QVBoxLayout
import threading
import math
import sys
class Gui:
def __init__(self,publisher):
self.publisher = publisher
self.widget = QWidget()
self.layout = QVBoxLayout(self.widget)
self.pushButton = QPushButton(self.widget)
self.pushButton.setText("Press to reset publisher")
self.pushButton.clicked.connect(self.publisher.resetCounter)
self.layout.addWidget( self.pushButton )
self.widget.setGeometry(50,50,320,200)
self.widget.show()
self.publisher.widget = self.widget
class DummyPublisher(Node):
def __init__(self):
super().__init__('dummy_publisher')
self.publisher_ = self.create_publisher(ChannelFloat32, 'topic', 10)
timer_period = 0.5 # seconds
self.timer = self.create_timer(timer_period, self.timer_callback)
self.resetCounter()
self.widget = None
self.t0 = self.get_clock().now().nanoseconds
def timer_callback(self):
msg = ChannelFloat32()
msg.values = [ float((self.get_clock().now().nanoseconds-self.t0)/1e9), float(self.i), float(math.sin(self.i)), float(self.i*4) ]
self.publisher_.publish(msg)
self.get_logger().info('Publishing: "%s"\n' % str(msg.values))
self.i += 1
if self.widget:
self.widget.setWindowTitle("Dummy publisher " + str(self.i))
def resetCounter(self):
self.i = 0
def ros_node_thread(ros_node):
executor = MultiThreadedExecutor()
executor.add_node(ros_node)
executor.spin()
def main(args=None):
rclpy.init(args=args)
app = QApplication(sys.argv)
publisher = DummyPublisher()
gui = Gui( publisher )
ros_node_thread_instance = threading.Thread(target=ros_node_thread, args=(publisher,))
ros_node_thread_instance.start()
try:
sys.exit(app.exec_())
finally:
publisher.destroy_node()
rclpy.shutdown()
ros_node_thread_instance.join()
if __name__ == '__main__':
main()
Subscriber:
import rclpy
from rclpy.node import Node
from rclpy.executors import MultiThreadedExecutor
from sensor_msgs.msg import ChannelFloat32
from PyQt5.QtWidgets import QApplication, QWidget, QVBoxLayout
from PyQt5.QtCore import pyqtSignal, QObject, QTimer
import PyQt5.QtCore
import threading
import sys
class Gui:
def __init__(self):
self.widget = QWidget()
self.layout = QVBoxLayout(self.widget)
self.widget.setGeometry(50,50,320,200)
self.widget.show()
class DummyListener(Node):
def __init__(self,gui):
super().__init__('dummy_listener')
self.gui = gui
self.subscription = self.create_subscription(
ChannelFloat32,
'topic',
self.listener_callback,
10)
self.subscription # prevent unused variable warning
self.gui = gui
self.count = 0
def listener_callback(self, msg):
self.get_logger().info('I heard: "%s"' % str(msg.values))
self.count += 1
self.gui.widget.setWindowTitle("Dummy listener " + str(self.count))
def ros_node_thread(ros_node):
executor = MultiThreadedExecutor()
executor.add_node(ros_node)
executor.spin()
def main(args=None):
rclpy.init(args=args)
app = QApplication(sys.argv)
gui = Gui()
listener = DummyListener( gui )
ros_node_thread_instance = threading.Thread(target=ros_node_thread, args=(listener,))
ros_node_thread_instance.start()
try:
sys.exit(app.exec_())
finally:
listener.destroy_node()
rclpy.shutdown()
ros_node_thread_instance.join()
if __name__ == '__main__':
main()
When I execute them from different consoles, running:
ros2 run my_package talker
ros2 run my_package listener
It just works fine, I see the two widgets, one with Dummy publisher # title being incremented and one with Dummy listener # title being incremented.
However, when I use a laucnh script:
from launch import LaunchDescription
import launch_ros.actions
def generate_launch_description():
return LaunchDescription([
launch_ros.actions.Node(
namespace= "talker", package='my_package', executable='talker'),
launch_ros.actions.Node(
namespace= "listener", package='my_package', executable='listener'),
])
The, I see the first widget with Dummy publisher # title being incremented and the other one's title remains unchanged as "python". By looking deeper, I see listener_callback never gets called.
Am I doing something wrong?
