在pyqt中拖动画布时，将画布绑定到窗口

from PyQt5.QtWidgets import QApplication, QGraphicsView, QGraphicsScene
from PyQt5.QtCore import Qt

class CanvasView(QGraphicsView):
    def __init__(self):
        super().__init__()
        
        self.scene = QGraphicsScene(self)
        self.setScene(self.scene)

class MainWindow(QMainWindow):
    def __init__(self):
        super().__init__()
        
        self.canvas = CanvasView()
        self.setCentralWidget(self.canvas)

rect = self.canvas.scene.addRect(0, 0, 100, 100)

class CanvasView(QGraphicsView):
    def __init__(self):
        super().__init__()
        
        self.scene = QGraphicsScene(self)
        self.setScene(self.scene)
        
        self.dragging = False
        self.last_pos = None
    
    def mousePressEvent(self, event):
        if event.button() == Qt.LeftButton:
            item = self.itemAt(event.pos())
            if item is not None:
                self.dragging = True
                self.last_pos = event.pos()
    
    def mouseMoveEvent(self, event):
        if self.dragging:
            delta = event.pos() - self.last_pos
            self.last_pos = event.pos()
            self.scene.setSceneRect(self.scene.sceneRect().translated(delta.x(), delta.y()))
    
    def mouseReleaseEvent(self, event):
        if event.button() == Qt.LeftButton:
            self.dragging = False

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