shahmirzali49/scrollable_positioned_list

scrollable_positioned_list

A flutter list that allows scrolling to a specific item in the list.

Also allows determining what items are currently visible.

Usage

A ScrollablePositionedList works much like the builder version of ListView except that the list can be scrolled or jumped to a specific item.

Example

A ScrollablePositionedList can be created with:

final ItemScrollController itemScrollController = ItemScrollController();
final ScrollOffsetController scrollOffsetController = ScrollOffsetController();
final ItemPositionsListener itemPositionsListener = ItemPositionsListener.create();
final ScrollOffsetListener scrollOffsetListener = ScrollOffsetListener.create()

ScrollablePositionedList.builder(
  itemCount: 500,
  itemBuilder: (context, index) => Text('Item $index'),
  itemScrollController: itemScrollController,
  scrollOffsetController: scrollOffsetController,
  itemPositionsListener: itemPositionsListener,
  scrollOffsetListener: scrollOffsetListener,
);

One then can scroll to a particular item with:

itemScrollController.scrollTo(
  index: 150,
  duration: Duration(seconds: 2),
  curve: Curves.easeInOutCubic);

or jump to a particular item with:

itemScrollController.jumpTo(index: 150);

One can monitor what items are visible on screen with:

itemPositionsListener.itemPositions.addListener(() => ...);

Experimental APIs (subject to bugs and changes)

Changes in scroll position can be monitored with:

scrollOffsetListener.changes.listen((event) => ...)

see ScrollSum in this test for an example of how the current offset can be calculated from the stream of scroll change deltas. This feature is new and experimental.

Changes in scroll position in pixels, relative to the current scroll position, can be made with:

scrollOffsetController.animateScroll(offset: 100, duration: Duration(seconds: 1));

A full example can be found in the example folder.

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This is not an officially supported Google product.