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Add initialValue parameter support for precise scroll positioning #3

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Add initialValue parameter support for precise scroll positioning #3

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74 changes: 69 additions & 5 deletions lib/animated_weight_picker.dart
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Original file line number Diff line number Diff line change
Expand Up @@ -27,6 +27,15 @@ class AnimatedWeightPicker extends StatefulWidget {
///
final double max;

/// Initial value to set the picker position
/// If not provided, defaults to min value
/// ```dart
///
/// 'Modified for initial value support'
/// ```
///
final double? initialValue;

/// Interval by value
///
/// ```dart
Expand Down Expand Up @@ -433,6 +442,7 @@ class AnimatedWeightPicker extends StatefulWidget {
//
required this.min,
required this.max,
this.initialValue, // Added initialValue parameter
//
this.division = 0.5,
//
Expand Down Expand Up @@ -481,6 +491,9 @@ class AnimatedWeightPicker extends StatefulWidget {
assert(!(max < 1)),
assert(!(min < 0)),
assert(!(max > 1000)),
assert(
initialValue == null || (initialValue >= min && initialValue <= max),
), // Added initialValue validation
assert(!(dialHeight > 110 || dialHeight < 3)),
assert(!(dialThickness > 5 || dialThickness < 0.5)),
assert(!(majorIntervalHeight > 110 || majorIntervalHeight < 3)),
Expand All @@ -507,11 +520,32 @@ class _AnimatedWeightPickerState extends State<AnimatedWeightPicker> {

final List<WheelModel> _valueList = [];
int _selectedIndex = 0;
late FixedExtentScrollController _scrollController; // Added scroll controller

@override
void initState() {
super.initState();
createWeightList(onInit: true);

// Calculate initial index based on initialValue
int initialIndex = 0;
if (widget.initialValue != null) {
double targetValue = widget.initialValue!.clamp(widget.min, widget.max);
double interval = widget.division.toPrecision(_divisionPrecision);
initialIndex = ((targetValue - widget.min) / interval).round().clamp(
0,
_valueList.length - 1,
);
}

_scrollController = FixedExtentScrollController(initialItem: initialIndex);
_selectedIndex = initialIndex;
}

@override
void dispose() {
_scrollController.dispose();
super.dispose();
}

void createWeightList({required bool onInit}) {
Expand Down Expand Up @@ -546,14 +580,39 @@ class _AnimatedWeightPickerState extends State<AnimatedWeightPicker> {
currentIndex++;
current += interval;
} while (current.toPrecision(2) <= widget.max);
if (!onInit) setState(() {});

// Update scroll controller when widget is updated
if (!onInit && mounted) {
// Recalculate initial position if initialValue changed
int newIndex = 0;
if (widget.initialValue != null) {
double targetValue = widget.initialValue!.clamp(widget.min, widget.max);
double intervalCalc = widget.division.toPrecision(_divisionPrecision);
newIndex = ((targetValue - widget.min) / intervalCalc).round().clamp(
0,
_valueList.length - 1,
);
}

// Only animate if the index actually changed
if (newIndex != _selectedIndex) {
_scrollController.animateToItem(
newIndex,
duration: const Duration(milliseconds: 300),
curve: Curves.easeInOut,
);
}

setState(() {});
}
}

@override
void didUpdateWidget(covariant AnimatedWeightPicker old) {
super.didUpdateWidget(old);
if (old.max == widget.max &&
old.min == widget.min &&
old.initialValue == widget.initialValue &&
old.division.toPrecision(_divisionPrecision) ==
widget.division.toPrecision(_divisionPrecision)) return;
createWeightList(onInit: false);
Expand All @@ -570,6 +629,7 @@ class _AnimatedWeightPickerState extends State<AnimatedWeightPicker> {
child: RotatedBox(
quarterTurns: -45,
child: ListWheelScrollView.useDelegate(
controller: _scrollController, // Added controller
offAxisFraction: 2,
perspective: 0.003,
itemExtent: 30,
Expand Down Expand Up @@ -680,7 +740,9 @@ class _AnimatedWeightPickerState extends State<AnimatedWeightPicker> {
mainAxisSize: MainAxisSize.min,
children: [
Text(
_valueList[_selectedIndex].value,
_selectedIndex < _valueList.length
? _valueList[_selectedIndex].value
: '',
style: widget.selectedValueStyle ??
TextStyle(
fontWeight: FontWeight.w700,
Expand All @@ -690,10 +752,12 @@ class _AnimatedWeightPickerState extends State<AnimatedWeightPicker> {
),
),
if (widget.showSuffix && widget.suffix == null)
Text(widget.suffixText,
style: TextStyle(color: widget.suffixTextColor))
Text(
widget.suffixText,
style: TextStyle(color: widget.suffixTextColor),
)
else if (widget.showSuffix && widget.suffix != null)
widget.suffix!
widget.suffix!,
],
),
],
Expand Down