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Description
final ItemScrollController itemScrollController = ItemScrollController();
final ItemPositionsListener itemPositionsListener = ItemPositionsListener.create();
...
ScrollablePositionedList.builder(
itemScrollController: itemScrollController,
itemPositionsListener: itemPositionsListener,
reverse: true,
itemCount: items.length,
itemBuilder: (context, i) => ListTile(...),
),
...
ValueListenableBuilder<Iterable<ItemPosition>>(
valueListenable: itemPositionsListener.itemPositions,
builder: (context, positions, child) {
int min;
int max;
if (positions.isNotEmpty) {
min = positions
.where((ItemPosition position) =>
position.itemTrailingEdge > 0)
.reduce((ItemPosition min, ItemPosition position) =>
position.itemTrailingEdge < min.itemTrailingEdge
? position
: min)
.index;
max = positions
.where((ItemPosition position) =>
position.itemLeadingEdge < 1)
.reduce((ItemPosition max, ItemPosition position) =>
position.itemLeadingEdge > max.itemLeadingEdge
? position
: max)
.index;
}
print( min); //prints 'null'
print(max); //prints 'null'
print(positions); //prints '[]'
return AnimatedSwitcher(
duration: _switcher400,
reverseDuration: _switcher400,
child: min ?? 0 < 5
? Container(height: 0, width: 0)
: RawMaterialButton(
padding: EdgeInsets.all(3),
constraints: BoxConstraints(minWidth: 50),
fillColor: Colors.white,
elevation: 10,
shape: CircleBorder(),
onPressed: () {
if (min ?? 0 < 15)
itemScrollController.scrollTo(
index: 0, duration: _switcher400);
else
itemScrollController.jumpTo(index: 0);
},
child: Icon(
Icons.arrow_drop_down,
size: 40,
),
),
);
},
),
Hi. This code was working fine a moment ago and then there is something wrong with it.
What am trying to acheive is animate in a button whenever the list is scrolled away from index 0 and the button will jump back to index 0. Simple.
The issue is itemPositionsListener.itemPositions is not returning the positions so i have no way to find out where i am in the list.