float _calculateScrollIncrement(ScrollableState state, ScrollIncrementType type = ScrollIncrementType.line)
{
D.assert(state.position != null);
D.assert(state.position.havePixels);
D.assert(state.widget.physics == null || state.widget.physics.shouldAcceptUserOffset(state.position));
if (state.widget.incrementCalculator != null)
{
return(state.widget.incrementCalculator(
new ScrollIncrementDetails(
type: type,
metrics: state.position
)
));
}
switch (type)
{
case ScrollIncrementType.line:
return(50.0f);
case ScrollIncrementType.page:
return(0.8f * state.position.viewportDimension);
}
return(0.0f);
}
internal _ScrollableScope(
Key key = null,
ScrollableState scrollable = null,
ScrollPosition position = null,
Widget child = null
) : base(key: key, child: child)
{
D.assert(scrollable != null);
D.assert(child != null);
this.scrollable = scrollable;
this.position = position;
}
public static Future ensureVisible(
BuildContext context,
float alignment = 0.0f,
TimeSpan?duration = null,
Curve curve = null,
ScrollPositionAlignmentPolicy alignmentPolicy = ScrollPositionAlignmentPolicy.explicitPolicy
)
{
duration = duration ?? TimeSpan.Zero;
curve = curve ?? Curves.ease;
List <Future> futures = new List <Future>();
ScrollableState scrollable = of(context);
while (scrollable != null)
{
futures.Add(scrollable.position.ensureVisible(
context.findRenderObject(),
alignment: alignment,
duration: duration,
curve: curve,
alignmentPolicy: alignmentPolicy
));
context = scrollable.context;
scrollable = of(context);
}
if (futures.isEmpty() || duration == TimeSpan.Zero)
{
return(Future.value());
}
if (futures.Count == 1)
{
return(futures.Single());
}
return(Future.wait <object>(futures));
}
public override void invoke(FocusNode node, Intent intent)
{
ScrollableState state = Scrollable.of(node.context);
D.assert(state != null, () => "ScrollAction was invoked on a context that has no scrollable parent");
D.assert(state.position.havePixels, () => "Scrollable must be laid out before it can be scrolled via a ScrollAction");
if (state.widget.physics != null && !state.widget.physics.shouldAcceptUserOffset(state.position))
{
return;
}
float increment = _getIncrement(state, intent as ScrollIntent);
if (increment == 0.0f)
{
return;
}
state.position.moveTo(
state.position.pixels + increment,
duration: TimeSpan.FromMilliseconds(100),
curve: Curves.easeInOut
);
}
public static IPromise ensureVisible(BuildContext context,
float alignment = 0.0f,
TimeSpan?duration = null,
Curve curve = null
)
{
duration = duration ?? TimeSpan.Zero;
curve = curve ?? Curves.ease;
List <IPromise> futures = new List <IPromise>();
ScrollableState scrollable = of(context);
while (scrollable != null)
{
futures.Add(scrollable.position.ensureVisible(
context.findRenderObject(),
alignment: alignment,
duration: duration,
curve: curve
));
context = scrollable.context;
scrollable = of(context);
}
if (futures.isEmpty() || duration == TimeSpan.Zero)
{
return(Promise.Resolved());
}
if (futures.Count == 1)
{
return(futures.Single());
}
return(Promise.All(futures));
}
float _getIncrement(ScrollableState state, ScrollIntent intent)
{
float increment = _calculateScrollIncrement(state, type: intent.type);
switch (intent.direction)
{
case AxisDirection.down:
switch (state.axisDirection)
{
case AxisDirection.up:
return(-increment);
case AxisDirection.down:
return(increment);
case AxisDirection.right:
case AxisDirection.left:
return(0.0f);
}
break;
case AxisDirection.up:
switch (state.axisDirection)
{
case AxisDirection.up:
return(increment);
case AxisDirection.down:
return(-increment);
case AxisDirection.right:
case AxisDirection.left:
return(0.0f);
}
break;
case AxisDirection.left:
switch (state.axisDirection)
{
case AxisDirection.right:
return(-increment);
case AxisDirection.left:
return(increment);
case AxisDirection.up:
case AxisDirection.down:
return(0.0f);
}
break;
case AxisDirection.right:
switch (state.axisDirection)
{
case AxisDirection.right:
return(increment);
case AxisDirection.left:
return(-increment);
case AxisDirection.up:
case AxisDirection.down:
return(0.0f);
}
break;
}
return(0.0f);
}
public override bool inDirection(FocusNode currentNode, TraversalDirection direction)
{
FocusScopeNode nearestScope = currentNode.nearestScope;
FocusNode focusedChild = nearestScope.focusedChild;
if (focusedChild == null)
{
FocusNode firstFocus = findFirstFocusInDirection(currentNode, direction) ?? currentNode;
switch (direction)
{
case TraversalDirection.up:
case TraversalDirection.left:
FocusTravesalUtils._focusAndEnsureVisible(
firstFocus,
alignmentPolicy: ScrollPositionAlignmentPolicy.keepVisibleAtStart
);
break;
case TraversalDirection.right:
case TraversalDirection.down:
FocusTravesalUtils._focusAndEnsureVisible(
firstFocus,
alignmentPolicy: ScrollPositionAlignmentPolicy.keepVisibleAtEnd
);
break;
}
return(true);
}
if (_popPolicyDataIfNeeded(direction, nearestScope, focusedChild))
{
return(true);
}
FocusNode found = null;
ScrollableState focusedScrollable = Scrollable.of(focusedChild.context);
switch (direction)
{
case TraversalDirection.down:
case TraversalDirection.up:
IEnumerable <FocusNode> eligibleNodes = _sortAndFilterVertically(
direction,
focusedChild.rect,
nearestScope.traversalDescendants
);
if (focusedScrollable != null && !focusedScrollable.position.atEdge())
{
IEnumerable <FocusNode> filteredEligibleNodes = LinqUtils <FocusNode> .WhereList(eligibleNodes, ((FocusNode node) => Scrollable.of(node.context) == focusedScrollable));
if (filteredEligibleNodes.Count() != 0)
{
eligibleNodes = filteredEligibleNodes;
}
}
if (eligibleNodes.Count() == 0)
{
break;
}
List <FocusNode> sorted = eligibleNodes.ToList();
if (direction == TraversalDirection.up)
{
//sorted = sorted.reversed.toList();
sorted.Reverse();
sorted = sorted.ToList();
}
Rect band = Rect.fromLTRB(focusedChild.rect.left, float.NegativeInfinity, focusedChild.rect.right, float.PositiveInfinity);
IEnumerable <FocusNode> inBand = LinqUtils <FocusNode> .WhereList(sorted, ((FocusNode node) => !node.rect.intersect(band).isEmpty));
if (inBand.Count() != 0)
{
found = inBand.First();
break;
}
FocusTravesalUtils.mergeSort <FocusNode>(sorted, compare: (FocusNode a, FocusNode b) => {
return((a.rect.center.dx - focusedChild.rect.center.dx).abs().CompareTo((b.rect.center.dx - focusedChild.rect.center.dx).abs()));
});
found = sorted.First();
break;
case TraversalDirection.right:
case TraversalDirection.left:
eligibleNodes = _sortAndFilterHorizontally(direction, focusedChild.rect, nearestScope);
if (focusedScrollable != null && !focusedScrollable.position.atEdge())
{
IEnumerable <FocusNode> filteredEligibleNodes = LinqUtils <FocusNode> .WhereList(eligibleNodes, ((FocusNode node) => Scrollable.of(node.context) == focusedScrollable));
if (filteredEligibleNodes.Count() != 0)
{
eligibleNodes = filteredEligibleNodes;
}
}
if (eligibleNodes.Count() == 0)
{
break;
}
sorted = eligibleNodes.ToList();
if (direction == TraversalDirection.left)
{
sorted.Reverse();
sorted = sorted.ToList();
//sorted = sorted.reversed.toList();
}
band = Rect.fromLTRB(float.NegativeInfinity, focusedChild.rect.top, float.PositiveInfinity, focusedChild.rect.bottom);
inBand = LinqUtils <FocusNode> .WhereList(sorted, ((FocusNode node) => !node.rect.intersect(band).isEmpty));
if (inBand.Count() != 0)
{
found = inBand.First();
break;
}
FocusTravesalUtils.mergeSort <FocusNode>(sorted, compare: (FocusNode a, FocusNode b) => {
return((a.rect.center.dy - focusedChild.rect.center.dy).abs().CompareTo((b.rect.center.dy - focusedChild.rect.center.dy).abs()));
});
found = sorted.First();
break;
}
if (found != null)
{
_pushPolicyData(direction, nearestScope, focusedChild);
switch (direction)
{
case TraversalDirection.up:
case TraversalDirection.left:
FocusTravesalUtils._focusAndEnsureVisible(
found,
alignmentPolicy: ScrollPositionAlignmentPolicy.keepVisibleAtStart
);
break;
case TraversalDirection.down:
case TraversalDirection.right:
FocusTravesalUtils._focusAndEnsureVisible(
found,
alignmentPolicy: ScrollPositionAlignmentPolicy.keepVisibleAtEnd
);
break;
}
return(true);
}
return(false);
}