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Flutter_Documentation

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}
Widget _buildTitleAndSubtitle() {
return Positioned(
left: 20,
bottom: 20,
child: Column(
mainAxisSize: MainAxisSize.min,
crossAxisAlignment: CrossAxisAlignment.start,
children: [
Text(
name,
style: const TextStyle(
color: Colors.white,
fontSize: 20,
fontWeight: FontWeight.bold,
),
),
Text(
country,
style: const TextStyle(
color: Colors.white,
fontSize: 14,
),
),
],
),
);
}
}
class ParallaxFlowDelegate extends FlowDelegate {
ParallaxFlowDelegate({
required this.scrollable,
required this.listItemContext,
required this.backgroundImageKey,
}) : super(repaint: scrollable.position);
final ScrollableState scrollable;
final BuildContext listItemContext;
final GlobalKey backgroundImageKey;
@override
BoxConstraints getConstraintsForChild(int i, BoxConstraints constraints) {
return BoxConstraints.tightFor(
width: constraints.maxWidth,
);
}
@override
void paintChildren(FlowPaintingContext context) {
// Calculate the position of this list item within the viewport.
final scrollableBox = scrollable.context.findRenderObject() as RenderBox;
final listItemBox = listItemContext.findRenderObject() as RenderBox;
final listItemOffset = listItemBox.localToGlobal(
listItemBox.size.centerLeft(Offset.zero),
ancestor: scrollableBox);
// Determine the percent position of this list item within the
// scrollable area.
final viewportDimension = scrollable.position.viewportDimension;
final scrollFraction =
(listItemOffset.dy / viewportDimension).clamp(0.0, 1.0);
// Calculate the vertical alignment of the background
// based on the scroll percent.
final verticalAlignment = Alignment(0.0, scrollFraction * 2 - 1);
// Convert the background alignment into a pixel offset for
// painting purposes.
final backgroundSize =
(backgroundImageKey.currentContext!.findRenderObject() as RenderBox)
.size;
final listItemSize = context.size;
final childRect =
verticalAlignment.inscribe(backgroundSize, Offset.zero & listItemSize);
// Paint the background.
context.paintChild(
0,
transform:
Transform.translate(offset: Offset(0.0, childRect.top)).transform,
);
}
@override
bool shouldRepaint(ParallaxFlowDelegate oldDelegate) {
return scrollable != oldDelegate.scrollable ||
listItemContext != oldDelegate.listItemContext ||
backgroundImageKey != oldDelegate.backgroundImageKey;
}
}
class Parallax extends SingleChildRenderObjectWidget {
const Parallax({
super.key,
required Widget background,
}) : super(child: background);
@override
RenderObject createRenderObject(BuildContext context) {
return RenderParallax(scrollable: Scrollable.of(context));
}
@override
void updateRenderObject(
BuildContext context, covariant RenderParallax renderObject) {
renderObject.scrollable = Scrollable.of(context);
}
}
class ParallaxParentData extends ContainerBoxParentData<RenderBox> {}
class RenderParallax extends RenderBox
with RenderObjectWithChildMixin<RenderBox>, RenderProxyBoxMixin {