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// Copyright 2014 The Flutter Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
import 'package:flutter/material.dart';
class _GesturePainter extends CustomPainter {
const _GesturePainter({
required this.zoom,
required this.offset,
required this.swatch,
required this.forward,
required this.scaleEnabled,
required this.tapEnabled,
required this.doubleTapEnabled,
required this.longPressEnabled,
});
final double zoom;
final Offset offset;
final MaterialColor swatch;
final bool forward;
final bool scaleEnabled;
final bool tapEnabled;
final bool doubleTapEnabled;
final bool longPressEnabled;
@override
void paint(Canvas canvas, Size size) {
final Offset center = size.center(Offset.zero) * zoom + offset;
final double radius = size.width / 2.0 * zoom;
final Gradient gradient = RadialGradient(
colors: forward
? <Color>[swatch.shade50, swatch.shade900]
: <Color>[swatch.shade900, swatch.shade50],
);
final Paint paint = Paint()
..shader = gradient.createShader(Rect.fromCircle(
center: center,
radius: radius,
));
canvas.drawCircle(center, radius, paint);
}
@override
bool shouldRepaint(_GesturePainter oldPainter) {
return oldPainter.zoom != zoom
|| oldPainter.offset != offset
|| oldPainter.swatch != swatch
|| oldPainter.forward != forward
|| oldPainter.scaleEnabled != scaleEnabled
|| oldPainter.tapEnabled != tapEnabled
|| oldPainter.doubleTapEnabled != doubleTapEnabled
|| oldPainter.longPressEnabled != longPressEnabled;
}
}
class GestureDemo extends StatefulWidget {
const GestureDemo({super.key});
@override
GestureDemoState createState() => GestureDemoState();
}
class GestureDemoState extends State<GestureDemo> {
late Offset _startingFocalPoint;
late Offset _previousOffset;
Offset _offset = Offset.zero;
late double _previousZoom;
double _zoom = 1.0;
static const List<MaterialColor> kSwatches = <MaterialColor>[
Colors.red,
Colors.pink,
Colors.purple,
Colors.deepPurple,
Colors.indigo,
Colors.blue,
Colors.lightBlue,
Colors.cyan,
Colors.green,
Colors.lightGreen,
Colors.lime,
Colors.yellow,
Colors.amber,
Colors.orange,
Colors.deepOrange,
Colors.brown,
Colors.grey,
Colors.blueGrey,
];
int _swatchIndex = 0;
MaterialColor _swatch = kSwatches.first;
MaterialColor get swatch => _swatch;
bool _forward = true;
bool _scaleEnabled = true;
bool _tapEnabled = true;
bool _doubleTapEnabled = true;
bool _longPressEnabled = true;
void _handleScaleStart(ScaleStartDetails details) {
setState(() {
_startingFocalPoint = details.focalPoint;
_previousOffset = _offset;
_previousZoom = _zoom;
});
}
void _handleScaleUpdate(ScaleUpdateDetails details) {
setState(() {
_zoom = _previousZoom * details.scale;
// Ensure that item under the focal point stays in the same place despite zooming
final Offset normalizedOffset = (_startingFocalPoint - _previousOffset) / _previousZoom;
_offset = details.focalPoint - normalizedOffset * _zoom;
});
}
void _handleScaleReset() {
setState(() {
_zoom = 1.0;
_offset = Offset.zero;
});
}
void _handleColorChange() {
setState(() {
_swatchIndex += 1;
if (_swatchIndex == kSwatches.length) {
_swatchIndex = 0;
}
_swatch = kSwatches[_swatchIndex];
});
}
void _handleDirectionChange() {
setState(() {
_forward = !_forward;
});
}
@override
Widget build(BuildContext context) {
return Stack(
fit: StackFit.expand,
children: <Widget>[
GestureDetector(
onScaleStart: _scaleEnabled ? _handleScaleStart : null,
onScaleUpdate: _scaleEnabled ? _handleScaleUpdate : null,
onTap: _tapEnabled ? _handleColorChange : null,
onDoubleTap: _doubleTapEnabled ? _handleScaleReset : null,
onLongPress: _longPressEnabled ? _handleDirectionChange : null,
child: CustomPaint(
painter: _GesturePainter(
zoom: _zoom,
offset: _offset,
swatch: swatch,
forward: _forward,
scaleEnabled: _scaleEnabled,
tapEnabled: _tapEnabled,
doubleTapEnabled: _doubleTapEnabled,
longPressEnabled: _longPressEnabled,
),
),
),
Positioned(
bottom: 0.0,
left: 0.0,
child: Card(
child: Container(
padding: const EdgeInsets.all(4.0),
child: Column(
crossAxisAlignment: CrossAxisAlignment.start,
children: <Widget>[
Row(
children: <Widget>[
Checkbox(
value: _scaleEnabled,
onChanged: (bool? value) { setState(() { _scaleEnabled = value!; }); },
),
const Text('Scale'),
],
),
Row(
children: <Widget>[
Checkbox(
value: _tapEnabled,
onChanged: (bool? value) { setState(() { _tapEnabled = value!; }); },
),
const Text('Tap'),
],
),
Row(
children: <Widget>[
Checkbox(
value: _doubleTapEnabled,
onChanged: (bool? value) { setState(() { _doubleTapEnabled = value!; }); },
),
const Text('Double Tap'),
],
),
Row(
children: <Widget>[
Checkbox(
value: _longPressEnabled,
onChanged: (bool? value) { setState(() { _longPressEnabled = value!; }); },
),
const Text('Long Press'),
],
),
],
),
),
),
),
],
);
}
}
void main() {
runApp(MaterialApp(
theme: ThemeData.dark(),
home: Scaffold(
appBar: AppBar(title: const Text('Gestures Demo')),
body: const GestureDemo(),
),
));
}