自定义CustomDelegate继承自QStyledItemDelegate，重写setModelData(self, editor, model, index)方法
def setModelData(self, editor, model, index):
#print("__________setModelData_________________")
print(model.data(index)) ##新的值,但是未保存到model中.
reply = QMessageBox.question(widget, "title",
"contenr",
QMessageBox.Yes | QMessageBox.No | QMessageBox.Cancel)
if reply == QMessageBox.Yes:
super(CustomDelegate, self).setModelData(editor, model, index)
print(model.data(index)) ##新的值已经保存到model中
