问题描述
我正在使用PyQt5和pyqtgraph绘制实时传感器数据。该图是更大的PyQt5应用程序的一部分，该应用程序用于与各种硬件进行交互并可视化传感器数据。
背景：以下代码是该代码的非常简化的示例，该代码负责查询传感器的数据，然后绘制瞬时位置及其移动平均值的图表。每隔x ms间隔在单独的线程中查询一次传感器。
问题：图形和传感器读数按预期工作。但是，在运行应用程序几秒钟后，pyqtgraph停止更新并冻结。一旦图表冻结，我唯一看到图表刷新/更新的地方是我是否尝试调整窗口大小或将焦点移到另一个窗口，然后重新聚焦回图表窗口。在这种情况下，图形将仅更新一次，并且不会继续刷新。
我在下面的链接中阅读了其他有类似问题的用户。但是，提出的解决方案不是从单独的线程更新GUI。就我而言，我不是从单独的线程更新图形。我仅使用单独的线程来收集传感器数据，然后发出带有新数据的信号。图的更新发生在主线程中。
import time
import numpy as np
from threading import Thread
import pyqtgraph as pg
import bottleneck as bn
import PyQt5
class MySensor():
def get_position(self,mean=0.0,standard_dev=0.1):
# Random sensor data
return np.random.normal(mean,standard_dev,1)[0]
class SignalCommunicate(PyQt5.QtCore.QObject):
# https://stackoverflow.com/a/45620056
got_new_sensor_data = PyQt5.QtCore.pyqtSignal(float,float)
position_updated = PyQt5.QtCore.pyqtSignal(float)
class LiveSensorViewer():
def __init__(self,sensor_update_interval=25):
# super().__init__()
# How frequently to get sensor data and update graph
self.sensor_update_interval = sensor_update_interval
# Init sensor object which gives live data
self.my_sensor = MySensor()
# Init with default values
self.current_position = self.my_sensor.get_position(mean=0.0,standard_dev=0.1)
self.current_position_timestamp = time.time()
# Init array which stores sensor data
self.log_time = [self.current_position_timestamp]
self.log_position_raw = [self.current_position]
self.moving_avg = 5
# Define the array size on max amount of data to store in the list
self.log_size = 1 * 60 * 1000/self.sensor_update_interval
# Setup the graphs which will display sensor data
self.plot_widget = pg.GraphicslayoutWidget(show=True)
self.my_graph = self.plot_widget.addplot(axisItems = {'bottom': pg.DateAxisItem()})
self.my_graph.showGrid(x=True,y=True,alpha=0.25)
self.my_graph.addLegend()
# Curves to be drawn on the graph
self.curve_position_raw = self.my_graph.plot(self.log_time,self.log_position_raw,name='Position raw (mm)',pen=pg.mkPen(color='#525252'))
self.curve_position_moving_avg = self.my_graph.plot(self.log_time,name='Position avg. 5 periods (mm)',pen=pg.mkPen(color='#FFF'))
# A dialog Box which displays the sensor value only. No graph.
self.my_dialog = PyQt5.QtWidgets.QWidget()
self.verticalLayout = PyQt5.QtWidgets.QVBoxLayout(self.my_dialog)
self.my_label = PyQt5.QtWidgets.QLabel()
self.verticalLayout.addWidget(self.my_label)
self.my_label.setText('Current sensor position:')
self.my_sensor_value = PyQt5.QtWidgets.QDoubleSpinBox()
self.verticalLayout.addWidget(self.my_sensor_value)
self.my_sensor_value.setDecimals(6)
self.my_dialog.show()
# Signals that can be emitted
self.signalComm = SignalCommunicate()
# Connect the signal 'position_updated' to the QDoubleSpinBox
self.signalComm.position_updated.connect(self.my_sensor_value.setValue)
# Setup thread which will continuously query the sensor for data
self.position_update_thread = Thread(target=self.read_position,args=(self.my_sensor,self.sensor_update_interval))
self.position_update_thread.daemon = True
self.position_update_thread.start() # Start the thread to query sensor data
def read_position(self,sensor_obj,update_interval ):
# This function continuously runs in a seprate thread to continuously query the sensor for data
sc = SignalCommunicate()
sc.got_new_sensor_data.connect(self.handle_sensor_data)
while True:
# Get data and timestamp from sensor
new_pos = sensor_obj.get_position(mean=0.0,standard_dev=0.1)
new_pos_time = time.time()
# Emit signal with sensor data and timestamp
sc.got_new_sensor_data.emit(new_pos,new_pos_time)
# Wait before querying the sensor again
time.sleep(update_interval/1000)
def handle_sensor_data(self,new_pos,new_pos_time ):
# Get the sensor position/timestamp emitted from the separate thread
self.current_position_timestamp = new_pos_time
self.current_position = new_pos
# Emit a singal with new position info
self.signalComm.position_updated.emit(self.current_position)
# Add data to log array
self.log_time.append(self.current_position_timestamp)
if len(self.log_time) > self.log_size:
# Append new data to the log and remove old data to maintain desired log size
self.log_time.pop(0)
self.log_position_raw.append(self.current_position)
if len(self.log_position_raw) > self.log_size:
# Append new data to the log and remove old data to maintain desired log size
self.log_position_raw.pop(0)
if len(self.log_time) <= self.moving_avg:
# Skip calculating moving avg if only 10 data points collected from sensor to prevent errors
return
else:
self.calculate_moving_avg()
# Request a graph update
self.update_graph()
def calculate_moving_avg(self):
# Get moving average of the position
self.log_position_moving_avg = bn.move_mean(self.log_position_raw,window=self.moving_avg,min_count=1)
def update_graph(self):
self.curve_position_raw.setData(self.log_time,self.log_position_raw)
self.curve_position_moving_avg.setData(self.log_time,self.log_position_moving_avg)
if __name__ == '__main__':
import sys
from PyQt5 import QtWidgets
app = QtWidgets.QApplication(sys.argv)
z = LiveSensorViewer()
app.exec_()
sys.exit(app.exec_())
解决方法
我能够找到原始问题的解决方案。我在下面发布了解决方案，并详细说明了原始问题发生的原因。
问题
原始问题中的图形被冻结，因为PyQtGraph是从单独的线程而不是主线程更新的。可以通过打印输出
来确定函数从哪个线程执行。threading.currentThread().getName()
在原始问题中，对update_graph()的调用是通过运行在单独线程中的handle_sensor_data()进行的。 handle_sensor_data()在单独的线程中运行的原因是，信号got_new_sensor_data的实例已连接到handle_sensor_data()内的插槽read_position()，该插槽也位于在单独的线程中运行。
解决方案
解决方案是通过发出一个信号来触发对update_graph()的调用，例如self.signalComm.request_graph_update.emit()内部的handle_sensor_data()。该信号request_graph_update必须从主线程即update_graph()内部连接到插槽__init__()。
下面是解决方案的完整代码。
import time
import numpy as np
import threading
from threading import Thread
import pyqtgraph as pg
import bottleneck as bn
import PyQt5
class MySensor():
def get_position(self,mean=0.0,standard_dev=0.1):
# Random sensor data
return np.random.normal(mean,standard_dev,1)[0]
class SignalCommunicate(PyQt5.QtCore.QObject):
# https://stackoverflow.com/a/45620056
got_new_sensor_data = PyQt5.QtCore.pyqtSignal(float,float)
position_updated = PyQt5.QtCore.pyqtSignal(float)
request_graph_update = PyQt5.QtCore.pyqtSignal()
class LiveSensorViewer():
def __init__(self,sensor_update_interval=25):
# super().__init__()
# How frequently to get sensor data and update graph
self.sensor_update_interval = sensor_update_interval
# Init sensor object which gives live data
self.my_sensor = MySensor()
# Init with default values
self.current_position = self.my_sensor.get_position(mean=0.0,standard_dev=0.1)
self.current_position_timestamp = time.time()
# Init array which stores sensor data
self.log_time = [self.current_position_timestamp]
self.log_position_raw = [self.current_position]
self.moving_avg = 5
# Define the array size on max amount of data to store in the list
self.log_size = 1 * 60 * 1000/self.sensor_update_interval
# Setup the graphs which will display sensor data
self.plot_widget = pg.GraphicsLayoutWidget(show=True)
self.my_graph = self.plot_widget.addPlot(axisItems = {'bottom': pg.DateAxisItem()})
self.my_graph.showGrid(x=True,y=True,alpha=0.25)
self.my_graph.addLegend()
# Curves to be drawn on the graph
self.curve_position_raw = self.my_graph.plot(self.log_time,self.log_position_raw,name='Position raw (mm)',pen=pg.mkPen(color='#525252'))
self.curve_position_moving_avg = self.my_graph.plot(self.log_time,name='Position avg. 5 periods (mm)',pen=pg.mkPen(color='#FFF'))
# A dialog box which displays the sensor value only. No graph.
self.my_dialog = PyQt5.QtWidgets.QWidget()
self.verticalLayout = PyQt5.QtWidgets.QVBoxLayout(self.my_dialog)
self.my_label = PyQt5.QtWidgets.QLabel()
self.verticalLayout.addWidget(self.my_label)
self.my_label.setText('Current sensor position:')
self.my_sensor_value = PyQt5.QtWidgets.QDoubleSpinBox()
self.verticalLayout.addWidget(self.my_sensor_value)
self.my_sensor_value.setDecimals(6)
self.my_dialog.show()
# Signals that can be emitted
self.signalComm = SignalCommunicate()
# Connect the signal 'position_updated' to the QDoubleSpinBox
self.signalComm.position_updated.connect(self.my_sensor_value.setValue)
# Update graph whenever the 'request_graph_update' signal is emitted
self.signalComm.request_graph_update.connect(self.update_graph)
# Setup thread which will continuously query the sensor for data
self.position_update_thread = Thread(target=self.read_position,args=(self.my_sensor,self.sensor_update_interval))
self.position_update_thread.daemon = True
self.position_update_thread.start() # Start the thread to query sensor data
def read_position(self,sensor_obj,update_interval ):
# print('Thread ={} Function = read_position()'.format(threading.currentThread().getName()))
# This function continuously runs in a seprate thread to continuously query the sensor for data
sc = SignalCommunicate()
sc.got_new_sensor_data.connect(self.handle_sensor_data)
while True:
# Get data and timestamp from sensor
new_pos = sensor_obj.get_position(mean=0.0,standard_dev=0.1)
new_pos_time = time.time()
# Emit signal with sensor data and timestamp
sc.got_new_sensor_data.emit(new_pos,new_pos_time)
# Wait before querying the sensor again
time.sleep(update_interval/1000)
def handle_sensor_data(self,new_pos,new_pos_time ):
print('Thread ={} Function = handle_sensor_data()'.format(threading.currentThread().getName()))
# Get the sensor position/timestamp emitted from the separate thread
self.current_position_timestamp = new_pos_time
self.current_position = new_pos
# Emit a singal with new position info
self.signalComm.position_updated.emit(self.current_position)
# Add data to log array
self.log_time.append(self.current_position_timestamp)
if len(self.log_time) > self.log_size:
# Append new data to the log and remove old data to maintain desired log size
self.log_time.pop(0)
self.log_position_raw.append(self.current_position)
if len(self.log_position_raw) > self.log_size:
# Append new data to the log and remove old data to maintain desired log size
self.log_position_raw.pop(0)
if len(self.log_time) <= self.moving_avg:
# Skip calculating moving avg if only 10 data points collected from sensor to prevent errors
return
else:
self.calculate_moving_avg()
# Request a graph update
# self.update_graph() # Uncomment this if you want update_graph() to run in the same thread as handle_sensor_data() function
# Emitting this signal ensures update_graph() will run in the main thread since the signal was connected in the __init__ function (main thread)
self.signalComm.request_graph_update.emit()
def calculate_moving_avg(self):
print('Thread ={} Function = calculate_moving_avg()'.format(threading.currentThread().getName()))
# Get moving average of the position
self.log_position_moving_avg = bn.move_mean(self.log_position_raw,window=self.moving_avg,min_count=1)
def update_graph(self):
print('Thread ={} Function = update_graph()'.format(threading.currentThread().getName()))
self.curve_position_raw.setData(self.log_time,self.log_position_raw)
self.curve_position_moving_avg.setData(self.log_time,self.log_position_moving_avg)
if __name__ == '__main__':
import sys
from PyQt5 import QtWidgets
app = QtWidgets.QApplication(sys.argv)
z = LiveSensorViewer()
app.exec_()
sys.exit(app.exec_())