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NOTES.md

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#BUGS

When collapsing/expanding a section, the header for the next section disappears while animation runs

#TESTING: - need to ensure this works fine for adapters which don't have footer views and which don't have header views (!!!) - need to test against different top/bottom padding scenarios

#RecyclerView.LayoutManager

Here's my understanding of how a linear layout manager works

  • When RV has a change to the number of items it represents, onLayoutChildren is called, and in there, a number of views are vended and positioned (precisely)

    • note that in the demo code log call, top is a sane number like -163 representing the top of the first item. items are stacked according to height until they fall off the bottom.

  • When user scrolls, scrollVerticallyBy is called

    • items are vertically shifted
    • new spaces are filled via same item vending process as onLayoutChildren
    • out of bounds items are recycled

firstPosition seems to be the position in the logical list of the first item on screen - it's used to know which item to vend from the adapter - firstPosition is updated on scroll and in recyling offscreen views

LayoutManager::getChildCount() returns number of views attached to RV, not number of hypothetical views in list