positioned_scroll_observer 2.2.1

positioned_scroll_observer: ^2.2.1 copied to clipboard

1. rename OnstageStrategy to VisibilityStrategy
2. introduce getVisibleItems to indicate which items are visible in the viewport
3. README update

1. support check the visible ratio of the observed RenderObject in a viewport
2. support aligning the observed RenderObject when showing it in the viewport.
3. add the GroupList example to show the usage of visibleRatioInViewport.

• see details: pull request

• deprecate RetainableScrollController, and introduce PositionRetainedScrollPhysics to achieve same goals.
• See details: pull request

• [new feature]: support RetainableScrollController to keep scroll offset when inserting a new item into the top of the ListView.

• See details: pull request

• fix: Issue #4

See PR details about the below changes.

• support SingleChildScrollView and ListWheelScrollView
• remove PositionedScrollController
• break changes of the design for supporting SliverScrollObserver and BoxScrollObserver.

• fix: not animating if item has been visible. Issue #1

• improve documentation
• fix: determine if the given index is visible when [SliverAppBar] is overlapped with other slivers.

• init release