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samples/material_3_demo/lib/elevation_screen.dart

174 lines
4.9 KiB

import 'package:flutter/material.dart';
class ElevationScreen extends StatelessWidget {
const ElevationScreen({super.key});
@override
Widget build(BuildContext context) {
Color shadowColor = Theme.of(context).colorScheme.shadow;
Color surfaceTint = Theme.of(context).colorScheme.primary;
return Expanded(
child: ListView(
children: [
Padding(
padding: const EdgeInsets.fromLTRB(16.0, 20, 16.0, 0),
child: Text(
'Surface Tint only',
style: Theme.of(context).textTheme.titleLarge,
),
),
ElevationGrid(surfaceTintColor: surfaceTint),
const SizedBox(height: 10),
Padding(
padding: const EdgeInsets.fromLTRB(16.0, 8.0, 16.0, 0),
child: Text(
'Surface Tint and Shadow',
style: Theme.of(context).textTheme.titleLarge,
),
),
ElevationGrid(
shadowColor: shadowColor,
surfaceTintColor: surfaceTint,
),
const SizedBox(height: 10),
Padding(
padding: const EdgeInsets.fromLTRB(16.0, 8.0, 16.0, 0),
child: Text(
'Shadow only',
style: Theme.of(context).textTheme.titleLarge,
),
),
ElevationGrid(shadowColor: shadowColor)
],
),
);
}
}
const double narrowScreenWidthThreshold = 450;
class ElevationGrid extends StatelessWidget {
const ElevationGrid({super.key, this.shadowColor, this.surfaceTintColor});
final Color? shadowColor;
final Color? surfaceTintColor;
List<ElevationCard> elevationCards(
Color? shadowColor, Color? surfaceTintColor) {
return elevations
.map(
(elevationInfo) => ElevationCard(
info: elevationInfo,
shadowColor: shadowColor,
surfaceTint: surfaceTintColor,
),
)
.toList();
}
@override
Widget build(BuildContext context) {
return Padding(
padding: const EdgeInsets.all(8),
child: LayoutBuilder(builder: (context, constraints) {
if (constraints.maxWidth < narrowScreenWidthThreshold) {
return GridView.count(
shrinkWrap: true,
crossAxisCount: 3,
children: elevationCards(shadowColor, surfaceTintColor),
);
} else {
return GridView.count(
shrinkWrap: true,
crossAxisCount: 6,
children: elevationCards(shadowColor, surfaceTintColor),
);
}
}),
);
}
}
class ElevationCard extends StatefulWidget {
const ElevationCard(
{super.key, required this.info, this.shadowColor, this.surfaceTint});
final ElevationInfo info;
final Color? shadowColor;
final Color? surfaceTint;
@override
State<ElevationCard> createState() => _ElevationCardState();
}
class _ElevationCardState extends State<ElevationCard> {
late double _elevation;
@override
void initState() {
super.initState();
_elevation = widget.info.elevation;
}
@override
Widget build(BuildContext context) {
const BorderRadius borderRadius = BorderRadius.all(Radius.circular(4.0));
final bool showOpacity = _elevation == widget.info.elevation;
final Color color = Theme.of(context).colorScheme.surface;
return Padding(
padding: const EdgeInsets.all(8.0),
child: Material(
borderRadius: borderRadius,
elevation: _elevation,
color: color,
shadowColor: widget.shadowColor,
surfaceTintColor: widget.surfaceTint,
type: MaterialType.card,
child: Padding(
padding: const EdgeInsets.all(8.0),
child: Column(
crossAxisAlignment: CrossAxisAlignment.start,
children: <Widget>[
Text(
'Level ${widget.info.level}',
style: Theme.of(context).textTheme.labelMedium,
),
Text(
'${widget.info.level.toInt()} dp',
style: Theme.of(context).textTheme.labelMedium,
),
if (showOpacity)
Expanded(
child: Align(
alignment: Alignment.bottomRight,
child: Text(
'${widget.info.overlayPercent}%',
style: Theme.of(context).textTheme.bodySmall,
),
),
),
],
),
),
),
);
}
}
class ElevationInfo {
const ElevationInfo(this.level, this.elevation, this.overlayPercent);
final int level;
final double elevation;
final int overlayPercent;
}
const List<ElevationInfo> elevations = <ElevationInfo>[
ElevationInfo(0, 0.0, 0),
ElevationInfo(1, 1.0, 5),
ElevationInfo(2, 3.0, 8),
ElevationInfo(3, 6.0, 11),
ElevationInfo(4, 8.0, 12),
ElevationInfo(5, 12.0, 14),
];