PySide:鼠标事件时可移动项的位置重置

import sys
from PySide2.QtWidgets import QApplication, QWidget, QLabel
from PySide2.QtCore import Qt

class DraggableItem(QWidget):
    def __init__(self, parent=None):
        super(DraggableItem, self).__init__(parent)
        self.setFixedSize(100, 100)
        self.setStyleSheet("background-color: red;")
        self.dragging = False
        self.offset = None

    def mousePressEvent(self, event):
        if event.button() == Qt.LeftButton:
            self.dragging = True
            self.offset = event.pos()

    def mouseMoveEvent(self, event):
        if self.dragging:
            self.move(event.globalPos() - self.offset)

    def mouseReleaseEvent(self, event):
        if event.button() == Qt.LeftButton:
            self.dragging = False

class MainWindow(QWidget):
    def __init__(self):
        super(MainWindow, self).__init__()
        self.setWindowTitle("Draggable Item Example")
        self.setGeometry(100, 100, 400, 300)

        item = DraggableItem(self)
        item.move(100, 100)

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