无法在 QWidget 上绘制 NavigationToolbar

Question

使用嵌入式matplotlib图开发多线程pyqt应用程序，但突然遇到奇怪的问题：无法在QWidget上绘制工具栏。我认为 pyqt 对象继承存在问题：据我所知 - 我有“主窗口”小部件（QWidget），它是“plotwidget”对象（QWidget）的父级，它是 Canvas 的父级。因此，要添加工具栏，我应该调用 NavigationToolbar(self.canvas, self.plotwidget) 但不幸的是，它什么也没给我。这是我的代码：

from PyQt5 import QtCore, QtGui, QtWidgets
from PyQt5.QtCore import QRunnable, QThreadPool
from PyQt5.QtCore import *

import queue as Queue

import matplotlib.pyplot as plt
from matplotlib.backends.backend_qt5agg import FigureCanvasQTAgg as FigureCanvas, NavigationToolbar2QT as NavigationToolbar

import sys

class Worker(QRunnable):
    def __init__(self , queue):
        QRunnable.__init__ ( self )
        self.queue = queue

    @pyqtSlot()
    def run(self):
        self.queue.put ( create_graph() ) 

class Canvas ( FigureCanvas ):

    def __init__(self, parent, figure):

        self.fig = figure
        FigureCanvas.__init__ ( self , self.fig )
        self.setParent ( parent )

class GUI (QtWidgets.QMainWindow):
    fig , axes = plt.subplots ( 1 , 1 , figsize = (2,2))

    def __init__(self):
        super().__init__()
        self.setupUi(self)

    def setupUi(self, MainWindow):
        MainWindow.setObjectName("MainWindow")
        MainWindow.resize(1800, 900)
        MainWindow.move(40,20)

        self.centralwidget = QtWidgets.QWidget(MainWindow)

        self.plotwidget = QtWidgets.QWidget(self.centralwidget)
        self.plotwidget.setGeometry ( QtCore.QRect (  30 , 400 , 811 , 381) )
        self.plotwidget.setParent ( self.centralwidget )
        plt.scatter ( [0 , 1 , 2 , 3 , 4 , 5] , [3 , 11 , 15 , 0 , 1 , 19] )

        self.canvas = Canvas(self, GUI.fig)
        self.canvas.setGeometry ( QtCore.QRect ( 30 , 400 , 811 , 1000 ) )
        self.canvas.setParent ( self.plotwidget )
        self.toolbar = NavigationToolbar ( self.canvas , self.plotwidget )

        MainWindow.setCentralWidget(self.centralwidget)

    
        self.scroll = QtWidgets.QScrollArea(self.centralwidget)
        self.scroll.setGeometry ( QtCore.QRect ( 30 , 400 , 811 , 381 )  )
        self.scroll.setWidget(self.canvas)

    def startCalc(self):

            self.queue = Queue.Queue ()
            self.threadpool = QThreadPool ()
            print ( "Multithreading with maximum %d threads" % self.threadpool.maxThreadCount () )
            worker = Worker (self.queue)
            self.threadpool.start ( worker )

            QtCore.QTimer.singleShot ( 500 , self.process_queue )

    def process_queue(self):
        try:
            self.canvas.draw ()

        except Queue.Empty:
            
            QtCore.QTimer.singleShot ( 500 , self.process_queue )

def main():
    global window
    app = QtWidgets.QApplication ( sys.argv )  
    window = GUI ()  
    window.show () 
    try:
        sys.exit ( app.exec_ () )
    except:
        print ( "Exiting" )

if __name__ == '__main__': 

    main ()  # то запускаем функцию main()

Answer 1

对不起，我不知道你为什么在示例中不调用startCalc 和process_queue 方法？试试看：

import sys
#import queue as Queue
from PyQt5 import QtCore, QtGui, QtWidgets
from PyQt5.QtCore import QRunnable, QThreadPool
from PyQt5.QtCore import pyqtSlot
import matplotlib.pyplot as plt
from matplotlib.backends.backend_qt5agg import FigureCanvasQTAgg as FigureCanvas, \
                                               NavigationToolbar2QT as NavigationToolbar


class Canvas(FigureCanvas):
    def __init__(self, parent, figure):
        self.fig = figure
        FigureCanvas.__init__(self, self.fig)
        self.setParent(parent)
        

class GUI(QtWidgets.QMainWindow):
    fig, axes = plt.subplots(1, 1, figsize=(2, 2))

    def __init__(self):
        super().__init__()
#        self.setupUi(self)
        self.initUi()

#    def setupUi(self, MainWindow):
    def initUi(self):  
        self.centralwidget = QtWidgets.QWidget(self) 
        self.setCentralWidget(self.centralwidget)
        
        plt.scatter([0 , 1 , 2 , 3 , 4 , 5], [3 , 11 , 15 , 0 , 1 , 19])

        self.canvas = Canvas(self, GUI.fig)
        self.toolbar = NavigationToolbar(self.canvas, self) 
        
        self.axes.set(xlabel='time (s)', ylabel='voltage (mV)',
               title='About as simple ...')
        self.axes.grid()

        layout = QtWidgets.QVBoxLayout(self.centralwidget)
        layout.addWidget(self.canvas)    
        layout.addWidget(self.toolbar)


def main():
#    global window
    app = QtWidgets.QApplication ( sys.argv )  
    window = GUI()
    window.resize(640, 480)
    window.show() 
#    try:
    sys.exit(app.exec_())
#    except:
#        print("Exiting")

if __name__ == '__main__': 
    main ()