当 matplotlib.FigureCanvas 嵌入 PyQt5 应用程序时，Matplotlib 回调不起作用？

Question

请您，StackOverflow 的干瘪长老们，

我正在尝试使用 PyQt5 制作一个小型 GUI 应用程序，其中 matplotlib.FigureCanvas 对象用作小部件来显示数据，我还希望通过使用 matplotlib 的回调函数来使其更具交互性。但是，这些回调似乎不适用于 PyQt5 窗口中嵌入的 FigureCanvas。

我认为实例化 Qt5 应用程序可能会干扰 matplotlib 的事件处理程序，但我不确定如何继续。有没有办法让 matplotlib 事件引发 Qt5 信号？我可以有两个单独的线程，两个事件处理程序都可以在其中运行吗？

下面的例子是我能简化的最简单的例子，它说明了这个问题。

案例 A：在 Matplotlib 窗口中运行

首先按原样运行，注意所需的行为：onclick 函数在弹出时在图中单击时被调用。 （还要注意第二个代码块，案例 B 不会在第一个之后运行）

案例 B：在 PyQt5 中运行

现在，注释掉Case A代码块，运行：点击图中不调用回调函数。

import sys
import numpy as np

from PyQt5 import QtCore, QtWidgets, uic

import matplotlib
matplotlib.use('QT5Agg')
import matplotlib.pylab as plt
from matplotlib.backends.backend_qt5agg import FigureCanvas
from matplotlib.backends.backend_qt5agg import NavigationToolbar2QT as NavigationToolbar
matplotlib.rcParams["toolbar"] = "toolmanager"

def onclick(event):
    '''example callback function'''
    print('got click: button=%d, x=%d, y=%d, xdata=%f, ydata=%f' %
          ( event.button, event.x, event.y, event.xdata, event.ydata))

class MPLWidget(QtWidgets.QWidget):
    '''
    Widget which should act like a matplotlib FigureCanvas, but embedded in PyQt5
    '''
    def __init__(self, parent=None, **kwargs):
        super().__init__(parent, **kwargs)
        
        # Making Matplotlib figure object with data
        fig, ax = plt.subplots()
        fig.suptitle("Plot in PyQt5: click and look in console")
        ax.plot(np.linspace(0,1,2))
        # Attaching matplotlib callback function which doesnt seem to work
        cid = fig.canvas.mpl_connect('button_press_event', onclick)

        self.layout = QtWidgets.QVBoxLayout(self)
        self.layout.setContentsMargins(0, 0, 0, 0)      
        self.plotWidget = FigureCanvas(fig)
        self.toolbar = NavigationToolbar(self.plotWidget, self)

        self.layout.addWidget(self.toolbar)
        self.layout.addWidget(self.plotWidget)


class TestWindow(QtWidgets.QMainWindow):
    '''Window which is a stand in for the larger PyQt5 application which needs a plot embedded'''
    def __init__(self):
        super().__init__()
        self.mplwidget = MPLWidget(self)
        self.setCentralWidget(self.mplwidget)

if __name__ == '__main__':

    # Case A: Using matplotlib without PyQt5, 
    # Note that the callback is triggered and something is printed when you click in the figure
    fig, ax = plt.subplots()
    fig.suptitle("Standalone matplotlib: click and look in console")
    ax.plot(np.linspace(0,1,2))
    cid = fig.canvas.mpl_connect('button_press_event', onclick)
    plt.show()
    
    # Case B:  Running PyQt5 + Matplotlib widget
    # Note that nothing is printed when you click in the figure
    app = QtWidgets.QApplication(sys.argv)
    window = TestWindow()
    window.show()
    sys.exit(app.exec_())

Answer 1

如果您要使用 pyqt5 中的 FigureCanvas 但使用 Figure() 构建，则不必使用“plt”，如 the official example 所示：

import sys
import numpy as np

from PyQt5 import QtCore, QtWidgets

import matplotlib

matplotlib.use("QT5Agg")

from matplotlib.backends.backend_qt5agg import FigureCanvas
from matplotlib.backends.backend_qt5agg import NavigationToolbar2QT as NavigationToolbar

matplotlib.rcParams["toolbar"] = "toolmanager"

from matplotlib.figure import Figure


def onclick(event):
    """example callback function"""
    print(
        "got click: button=%d, x=%d, y=%d, xdata=%f, ydata=%f"
        % (event.button, event.x, event.y, event.xdata, event.ydata)
    )


class MPLWidget(QtWidgets.QWidget):
    """
    Widget which should act like a matplotlib FigureCanvas, but embedded in PyQt5
    """

    def __init__(self, parent=None, **kwargs):
        super().__init__(parent, **kwargs)

        # Making Matplotlib figure object with data
        self.canvas = FigureCanvas(Figure())
        ax = self.canvas.figure.add_subplot(111)
        ax.set_title("Plot in PyQt5: click and look in console")
        ax.plot(np.linspace(0, 1, 2))

        cid = self.canvas.mpl_connect("button_press_event", onclick)

        self.layout = QtWidgets.QVBoxLayout(self)
        self.layout.setContentsMargins(0, 0, 0, 0)
        self.toolbar = NavigationToolbar(self.canvas, self)

        self.layout.addWidget(self.toolbar)
        self.layout.addWidget(self.canvas)


class TestWindow(QtWidgets.QMainWindow):
    """Window which is a stand in for the larger PyQt5 application which needs a plot embedded"""

    def __init__(self):
        super().__init__()
        self.mplwidget = MPLWidget(self)
        self.setCentralWidget(self.mplwidget)


if __name__ == "__main__":
    app = QtWidgets.QApplication(sys.argv)
    window = TestWindow()
    window.show()
    sys.exit(app.exec_())