[FLEX-35369] RTE: DragProxy Error

• Type: Bug
• Status: Open
• Priority: Major
• Resolution: Unresolved
• Affects Version/s: Apache Flex 4.16.0
• Fix Version/s: Apache Flex 4.16.1
• Component/s: Spark: Window
• Environment: Windows 10
• Assignee: Unassigned
• Reporter: John Hall
• Created: 08/Dec/17 17:19
• Updated: 08/Dec/17 17:21

Description

Working with NativeDragDrop on occasion I get the following error

TypeError: Error #1009: Cannot access a property or method of a null object reference.
at mx.managers.dragClasses::DragProxy/mouseUpHandler()[/Users/justinmclean/Documents/ApacheFlex4.16/frameworks/projects/framework/src/mx/managers/dragClasses/DragProxy.as:660]
at mx.managers.dragClasses::DragProxy/mouseLeaveHandler()[/Users/justinmclean/Documents/ApacheFlex4.16/frameworks/projects/framework/src/mx/managers/dragClasses/DragProxy.as:561]
at flash.events::EventDispatcher/dispatchEventFunction()
at flash.events::EventDispatcher/dispatchEvent()
at mx.managers::WindowedSystemManager/mouseLeaveHandler()[/Users/justinmclean/Documents/ApacheFlex4.16/frameworks/projects/airframework/src/mx/managers/WindowedSystemManager.as:2306]

Alex Harui's comment on the forum was:

_Hi,

The stack trace points out a legitimate bug. If the Drag starts, but then
the mouse goes out of the app and the button is released without any
mouseMove events coming into the DragProxy, the lastMouseEvent has not
been set and you'll get this crash.

I'm not quite sure how you can get zero "mouseMove" events, but maybe if
you drag fast enough while the app is computing the thing to drag.

File a bug if you can. You shouldn't need to build the SDK to fix this
problem. You can use monkey-patching instead. Search the internet for
articles on "Flex Monkey Patching".

Thanks,
-Alex
_