如何使用 NSDraggingInfo 或类似方法检测拖动操作是否被取消？
我创建了 NSImageView 的子类，并实现了在同一类的其他实例之间拖动图像的非正式协议。我在拖动操作之前保留对视图图像的引用，并且能够在给定某些条件的情况下将其设置回所述图像。
但是，我似乎无法检测拖动操作是否被取消。我知道 DraggingEnded 方法被调用，但当拖动成功时它也会被调用。有什么想法吗？
I've created a subclass of NSImageView and implemented the informal protocol for dragging images between other instances of the same class. I am keeping a reference to the image of the view prior to the dragging operation and am able to set it back to said image given certain criteria.
However, I can't seem to detect if the dragging operation was cancelled. I know that the draggingEnded method is called but it is also called when a drag was successful. Any ideas?
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我遇到了类似的需求。事实上，您可以检查传递给 NSDraggingSource 协议方法
draggedImage:endAt:operation:的operation参数来检测拖动取消，这一事实并没有很好的记录。在
draggedImage:endAt:operation:方法中只需添加以下检查：I encountered a similar requirement. The fact that you can examine the
operationargument passed to the NSDraggingSource protocol methoddraggedImage:endedAt:operation:to detect drag cancellation is not very well documented.In the
draggedImage:endedAt:operation:method just add the following check: