SwiftUI 拖放错误“NSInternalInconsistencyException”

Question

I have a swiftUI app that implements the native drag and drop apis. Everything works well but I have discovered an edge case that I don't understand how to fix. Essentially the entire view of the app (the size of the device screen) is a drop target. When dragging an object to be dropped, if the user moves the item to the edge of the screen the app will crash throwing the error:

'NSInternalInconsistencyException', reason: UIDragPreviewTarget requires that the container view is in a window, but it is not

I assume this has to do with the drop target and trying to move the drag object out of the app's window, but I don't know what to do to handle this edge case.

Any help would be greatly appreciated

EDIT: I commented out the .onDrop() modifier and the crash still persists. I can only guess that the generated UIDragPreviewTarget is tracking its location internally but when it is pulled out of the Frame of the app it throws the error

Answer 1

After digging around a bunch more and creating a new simplified project to demonstrate this wasn't a bug in the Drag and Drop implementation in SwiftUI, I think I found the issue.

In my case I have a view that holds the data I need sitting above the view I want to be able to drag that data into. While in the drag process, I wanted the top view to dismiss itself so as to no longer obstruct the lower view. I was flipping this switch in one of two ways.

1. when starting the drag process on the original piece of data, I started a timer that would give you 1.5 seconds to cancel the drop before it would hide the view.
2. when entering the lower view's drop target, it would close the top view

Removing both of these actions eliminated the crash.

My assumption at this point is that hiding the original source of the data is tripping up the dragItem's sense of "home" and when you try and drag it off screen it has no where to return back too.