如何在回调函数ROS中使用fig.canvas.draw()

Question

我正试图在ros中可视化消息，但我无法在回调中放入fig.canvas.draw((。我的目标是不断更新图表。但每次尝试时，我都会得到错误"主线程不在主循环中"。我该如何解决此问题？

#! /usr/bin/env python
import rospy
import numpy as np
import matplotlib.pyplot as plt
import matplotlib.animation as animation
import random

from sensor_msgs.msg import LaserScan
x = np.linspace(0, 2* np.pi, 100)
y=np.random.random_integers(1, 100, 100)
plt.ion()
fig = plt.figure()
ax = fig.add_subplot(111)
line1, = ax.plot(x, y, 'b-')
def callback(scan):
distance_list = scan.ranges
print(distance_list)
print("scan angle min", scan.angle_min)
print("scan angle incr", scan.angle_increment)
print("scan angle max", scan.angle_max)
line1.set_ydata(distance_list)
fig.canvas.draw()
rospy.init_node('lidar_visual_node')
sub = rospy.Subscriber('scan', LaserScan, callback)
rospy.spin()

Answer 1

这里的问题是回调在一个单独的线程中运行，并且不能访问主线程中的fig。一个包含回调和所需变量的对象可以通过引入持久性来解决这个问题。

class Visualiser:
def __init__(self):
x = np.linspace(0, 2* np.pi, 100)
y = np.random.random_integers(1, 100, 100)
plt.ion()
self.fig = plt.figure()
ax = self.fig.add_subplot(111)
self.line1, = ax.plot(x, y, 'b-')
def scanner_callback(self, scan):
distance_list = scan.ranges
print(distance_list)
print("scan angle min", scan.angle_min)
print("scan angle incr", scan.angle_increment)
print("scan angle max", scan.angle_max)
self.line1.set_ydata(distance_list)
self.fig.canvas.draw()

rospy.init_node('lidar_visual_node')
vis = Visualiser()
sub = rospy.Subscriber('scan', LaserScan, vis.scanner_callback)
rospy.spin()