如何以编程方式退出QListWidget中的拖放操作？

Question

我正在使用一个简单显示对象列表的QListWidget。我允许用户通过内部拖放来重新排序这些项目。一切正常，但我现在需要在用户尝试删除（重新排序）时添加检查，如果检查失败，请以编程方式重新建立原始订单。这是我得到的：

class SequenceControl(QListWidget): 
    def __init__(self, parent = None): 
     super(SequenceControl, self).__init__(parent) 

     self.initialIndex = 0 
     self.selectedObject = None 
     self.setAcceptDrops(True) 
     self.setDragEnabled(True) 
     self.setDragDropMode(QAbstractItemView.InternalMove) 


    def dragEnterEvent(self, event): 
     super(SequenceControl, self).dragEnterEvent(event) 

     self.selectedObject = self.currentItem() 
     self.initialIndex = self.currentRow() 

    def dropEvent(self, event): 
     super(SequenceControl, self).dropEvent(event) 

     # Some logic here (not shown) to see if the drop is not 
     # allowed. Assume it isn't: 
     warningDialog = MyWarningDialog(self.parent) 
     ProceedAnyway = warningDialog.exec_() 

     if ProceedAnyway: 
      # Do stuff... 
     else: 
      # Here's the problem. I need to place the item being dropped 
      # back in its initial pre-drag/drop location. The following 
      # naïve attempt doesn't work: 
      self.insertItem(self.initialIndex, self.selectedObject) 

以上绝对是错误的（我相信），因为它可能会重复项目。但除此之外，问题在于它似乎没有效果。我认为放弃事件重写我在重新排序方面的任何事情。但这只是一个理论。有谁知道正确的方法来做到这一点？

Answer 1

要恢复更改，我们必须首先删除目标项目，为此我们使用takeItem()，除了删除它将返回项目，然后在insertItem()函数的帮助下将其插入源位置。

class SequenceControl(QListWidget): 
    def __init__(self, parent=None): 
     super(SequenceControl, self).__init__(parent) 

     self.fromPos = None 
     self.setAcceptDrops(True) 
     self.setDragEnabled(True) 
     self.setDragDropMode(QAbstractItemView.InternalMove) 

    def dragEnterEvent(self, event): 
     super(SequenceControl, self).dragEnterEvent(event) 
     self.fromPos = self.currentRow() 

    def dropEvent(self, event): 
     super(SequenceControl, self).dropEvent(event) 

     reply = QMessageBox.question(None, "Revert to Drag and Drop", 
            "Do you want to keep the change?", 
            QMessageBox.Yes | QMessageBox.No) 
     if reply == QMessageBox.Yes: 
      print("Do stuff...") 
     else: 
      currentItem = self.takeItem(self.currentRow()) 
      self.insertItem(self.fromPos, currentItem)