layoutChild method
- @protected
@protected
Lays out the child.
This is called by performLayout. It applies the given scrollOffset
(which need not match the offset given by the constraints) and the
maxExtent
(which need not match the value returned by the maxExtent
getter).
The overlapsContent
argument is passed to updateChild.
Implementation
@protected
void layoutChild(double scrollOffset, double maxExtent, { bool overlapsContent = false }) {
assert(maxExtent != null);
final double shrinkOffset = math.min(scrollOffset, maxExtent);
if (_needsUpdateChild || _lastShrinkOffset != shrinkOffset || _lastOverlapsContent != overlapsContent) {
invokeLayoutCallback<SliverConstraints>((SliverConstraints constraints) {
assert(constraints == this.constraints);
updateChild(shrinkOffset, overlapsContent);
});
_lastShrinkOffset = shrinkOffset;
_lastOverlapsContent = overlapsContent;
_needsUpdateChild = false;
}
assert(minExtent != null);
assert(() {
if (minExtent <= maxExtent)
return true;
throw FlutterError(
'The maxExtent for this $runtimeType is less than its minExtent.\n'
'The specified maxExtent was: ${maxExtent.toStringAsFixed(1)}\n'
'The specified minExtent was: ${minExtent.toStringAsFixed(1)}\n'
);
}());
child?.layout(
constraints.asBoxConstraints(maxExtent: math.max(minExtent, maxExtent - shrinkOffset)),
parentUsesSize: true,
);
}