如何在 QWidget 中的 matplot 画布上跟踪鼠标？

Question

我想实时跟踪鼠标在 matplot 画布上的位置。

现在，我构建了一个 MplWidget，它继承了 Qwidget（就像一个容器），然后在它上面构建了一个画布来显示绘图。但是，问题是我只能在除画布区域之外的填充区域中跟踪鼠标的位置。

由于我的画布继承了不是 QWidget 的 matplotlib.figure，因此它没有 setMouseTracking() 属性。这样，如何解决这个问题？

我发现了一个非常有用的链接How to return mouse coordinates in realtime?。然而，它也面临同样的问题。当鼠标在标签（文本区域）上时，跟踪功能似乎被中断了。

我的这个类的代码如下所示：

from PyQt5.QtWidgets import *

from matplotlib.backends.backend_qt5agg import FigureCanvasQTAgg as FigureCanvas

from matplotlib.figure import Figure


class MplWidget(QWidget):

    def __init__(self, parent=None):
        # QWidget.__init__(self, parent)
        super(QWidget, self).__init__(parent)

        self.canvas = FigureCanvas(Figure())

        vertical_layout = QVBoxLayout()
        vertical_layout.addWidget(self.canvas)

        self.canvas.axes = self.canvas.figure.add_subplot(111)
        self.setLayout(vertical_layout)

        self.setMouseTracking(True)

    def mouseMoveEvent(self, e):
        text = "x: {0},  y: {1}".format(e.x(), e.y())
        print(text)
        super(MplWidget, self).mouseMoveEvent(e)

    def mousePressEvent(self, e):
        print('click!')

Answer 1

您已经注意到画布不是由 Qt 而是由 matplotlib 处理的，因此解决方案是使用该库提供的事件，如果您查看the docs，您会看到以下事件：

事件名称 类别和描述

'button_press_event'  MouseEvent - mouse button is pressed
'button_release_event'    MouseEvent - mouse button is released
'draw_event'  DrawEvent - canvas draw (but before screen update)
'key_press_event' KeyEvent - key is pressed
'key_release_event'   KeyEvent - key is released
'motion_notify_event' MouseEvent - mouse motion
'pick_event'  PickEvent - an object in the canvas is selected
'resize_event'    ResizeEvent - figure canvas is resized
'scroll_event'    MouseEvent - mouse scroll wheel is rolled
'figure_enter_event'  LocationEvent - mouse enters a new figure
'figure_leave_event'  LocationEvent - mouse leaves a figure
'axes_enter_event'    LocationEvent - mouse enters a new axes
'axes_leave_event'    LocationEvent - mouse leaves an axes

在您的情况下，您应该使用事件：

• button_press_event
• button_release_event
• motion_notify_event

例子：

from PyQt5 import QtWidgets

from matplotlib.backends.backend_qt5agg import FigureCanvasQTAgg as FigureCanvas
from matplotlib.figure import Figure


class MplWidget(QtWidgets.QWidget):
    def __init__(self, parent=None):
        super(MplWidget, self).__init__(parent)
        self.canvas = FigureCanvas(Figure())

        vertical_layout = QtWidgets.QVBoxLayout(self)
        vertical_layout.addWidget(self.canvas)

        self.canvas.axes = self.canvas.figure.add_subplot(111)

        self.canvas.mpl_connect("button_press_event", self.on_press)
        self.canvas.mpl_connect("button_release_event", self.on_release)
        self.canvas.mpl_connect("motion_notify_event", self.on_move)

    def on_press(self, event):
        print("press")
        print("event.xdata", event.xdata)
        print("event.ydata", event.ydata)
        print("event.inaxes", event.inaxes)
        print("x", event.x)
        print("y", event.y)

    def on_release(self, event):
        print("release:")
        print("event.xdata", event.xdata)
        print("event.ydata", event.ydata)
        print("event.inaxes", event.inaxes)
        print("x", event.x)
        print("y", event.y)

    def on_move(self, event):
        print("move")
        print("event.xdata", event.xdata)
        print("event.ydata", event.ydata)
        print("event.inaxes", event.inaxes)
        print("x", event.x)
        print("y", event.y)


if __name__ == "__main__":
    import sys

    app = QtWidgets.QApplication(sys.argv)
    w = MplWidget()
    w.show()
    sys.exit(app.exec_())