基于以下代码，怎么实现拖拽功能？ self.figure = Figure() self.canvas = FigureCanvas(self.figure)

要实现拖拽功能，你需要将canvas绑定鼠标按下、移动、释放事件，并在事件处理函数中实现拖拽逻辑。具体步骤如下：

1. 在初始化函数中添加以下代码，将canvas绑定鼠标事件：

self.canvas.mpl_connect('button_press_event', self.on_press)
self.canvas.mpl_connect('motion_notify_event', self.on_motion)
self.canvas.mpl_connect('button_release_event', self.on_release)

2. 实现事件处理函数。在on_press函数中获取鼠标按下时的位置，并记录下当前图像的偏移量。在on_motion函数中计算出鼠标移动的距离，并将图像的偏移量加上这个距离，更新图像的位置。在on_release函数中清空记录的偏移量。

def on_press(self, event):
    if event.button == 1:
        self.press = (event.x, event.y)
        self.offset = self.figure.transFigure.transform(self.figure.transData.inverted().transform((event.x, event.y)))

def on_motion(self, event):
    if self.press is not None:
        dx = event.x - self.press[0]
        dy = event.y - self.press[1]
        self.offset += (dx / self.canvas.get_width_height()[0], dy / self.canvas.get_width_height()[1])
        self.figure.subplots_adjust(left=self.offset[0], bottom=self.offset[1], right=1 - self.offset[0], top=1 - self.offset[1])
        self.canvas.draw()

def on_release(self, event):
    if event.button == 1:
        self.press = None

注意，这里的偏移量是指图像在画布中的位置偏移量，需要通过Figure对象的transFigure和transData属性进行转换。同时，在每次更新图像位置后，需要调用canvas的draw方法重新绘制画布。

完整的代码如下所示：

from matplotlib.figure import Figure
from matplotlib.backends.backend_qt5agg import FigureCanvasQTAgg as FigureCanvas
from PyQt5.QtWidgets import QApplication, QMainWindow, QVBoxLayout, QWidget

class MainWindow(QMainWindow):
    def __init__(self):
        super().__init__()
        self.figure = Figure()
        self.canvas = FigureCanvas(self.figure)
        self.press = None
        self.offset = (0, 0)
        self.init_ui()

    def init_ui(self):
        widget = QWidget()
        layout = QVBoxLayout(widget)
        layout.addWidget(self.canvas)
        self.setCentralWidget(widget)
        self.canvas.mpl_connect('button_press_event', self.on_press)
        self.canvas.mpl_connect('motion_notify_event', self.on_motion)
        self.canvas.mpl_connect('button_release_event', self.on_release)

    def on_press(self, event):
        if event.button == 1:
            self.press = (event.x, event.y)
            self.offset = self.figure.transFigure.transform(self.figure.transData.inverted().transform((event.x, event.y)))

    def on_motion(self, event):
        if self.press is not None:
            dx = event.x - self.press[0]
            dy = event.y - self.press[1]
            self.offset += (dx / self.canvas.get_width_height()[0], dy / self.canvas.get_width_height()[1])
            self.figure.subplots_adjust(left=self.offset[0], bottom=self.offset[1], right=1 - self.offset[0], top=1 - self.offset[1])
            self.canvas.draw()

    def on_release(self, event):
        if event.button == 1:
            self.press = None

if __name__ == '__main__':
    app = QApplication([])
    window = MainWindow()
    window.show()
    app.exec_()