Placeholder doesn't work during scrolling through dragging

[chaudharydeepanshu]

The provided placeholder doesn't work during scrolling through dragging.

screen-20221014-202154.2.mp4

I found that the _dragging variable in ReorderableItemViewState from reorderable_item.dart only becomes true for elements that were visible at the start of drag but after continuous scrolling, through drag, it never becomes true for the newly generated elements by the builder.

I was unable to resolve that as I'm very unfamiliar with the code.

Thank you.

[huhuang03]

After some debug, I found it's a can't resovle issue in current implemention.

The reason the placeholder is gone is: the placeholdre is implements like this:

Transform(
    child: buildBy(dragging child)
    offset: calcTheOffset()
)

The offset is right, but after scroll down, the parent grdiview is ignore showing the dragging widget child. I can't find a way to resolve this. I'm sorry for this.

Maybe you can try this project reorderables or flutter-reorderable-grid-view. They are seems very powerful.