當 matplotlib.FigureCanvas 嵌入到 PyQt5 應用程序中時，Matplotlib 回調不起作用？

Question

Prithee，StackOverflow 的干癟長老，

我正在嘗試使用 PyQt5 制作一個小型 GUI 應用程序，將 matplotlib.FigureCanvas 對象用作小部件來顯示數據，我還想通過使用 matplotlib 的回調函數使數據更具交互性。 但是，這些回調似乎不適用於嵌入在 PyQt5 窗口中的 FigureCanvas。

我認為實例化 Qt5 應用程序可能會干擾 matplotlib 的事件處理程序，但我不確定如何繼續。 有沒有辦法讓 matplotlib 事件引發 Qt5 信號？ 我可以有兩個單獨的線程，兩個事件處理程序都可以在其中運行嗎？

下面的示例是我可以縮減的最簡單的事情，它說明了這個問題。

案例 A：在 Matplotlib 窗口中運行

首先按原樣運行，注意所需的行為： onclick函數在圖形彈出后在單擊時調用。 （還要注意第二個代碼塊，案例 B 不會在第一個之后運行）

案例 B：在 PyQt5 中運行

現在，注釋掉 Case A 代碼塊，然后運行：點擊圖中沒有調用回調函數。

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，則不必使用“plt”，而是使用 Figure() 進行構建，如官方示例所示：

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_())