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// Copyright 2015 The Chromium 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({
this.zoom,
this.offset,
this.swatch,
this.forward,
this.scaleEnabled,
this.tapEnabled,
this.doubleTapEnabled,
this.longPressEnabled
});
final double zoom;
final Offset offset;
final Map<int, Color> swatch;
final bool forward;
final bool scaleEnabled;
final bool tapEnabled;
final bool doubleTapEnabled;
final bool longPressEnabled;
void paint(Canvas canvas, Size size) {
Point center = (size.center(Point.origin).toOffset() * zoom + offset).toPoint();
double radius = size.width / 2.0 * zoom;
Gradient gradient = new RadialGradient(
center: center, radius: radius,
colors: forward ? <Color>[swatch[50], swatch[900]]
: <Color>[swatch[900], swatch[50]]
);
Paint paint = new Paint()
..shader = gradient.createShader();
canvas.drawCircle(center, radius, paint);
}
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 StatefulComponent {
_GestureDemoState createState() => new _GestureDemoState();
}
class _GestureDemoState extends State<GestureDemo> {
Point _startingFocalPoint;
Offset _previousOffset;
Offset _offset = Offset.zero;
double _previousZoom;
double _zoom = 1.0;
Map<int, Color> _swatch = Colors.blue;
bool _forward = true;
bool _scaleEnabled = true;
bool _tapEnabled = true;
bool _doubleTapEnabled = true;
bool _longPressEnabled = true;
void _handleScaleStart(Point focalPoint) {
setState(() {
_startingFocalPoint = focalPoint;
_previousOffset = _offset;
_previousZoom = _zoom;
});
}
void _handleScaleUpdate(double scale, Point focalPoint) {
setState(() {
_zoom = (_previousZoom * scale);
// Ensure that item under the focal point stays in the same place despite zooming
Offset normalizedOffset = (_startingFocalPoint.toOffset() - _previousOffset) / _previousZoom;
_offset = focalPoint.toOffset() - normalizedOffset * _zoom;
});
}
void _handleScaleReset() {
setState(() {
_zoom = 1.0;
_offset = Offset.zero;
});
}
void _handleColorChange() {
setState(() {
switch (_swatch) {
case Colors.blueGrey: _swatch = Colors.red; break;
case Colors.red: _swatch = Colors.pink; break;
case Colors.pink: _swatch = Colors.purple; break;
case Colors.purple: _swatch = Colors.deepPurple; break;
case Colors.deepPurple: _swatch = Colors.indigo; break;
case Colors.indigo: _swatch = Colors.blue; break;
case Colors.blue: _swatch = Colors.lightBlue; break;
case Colors.lightBlue: _swatch = Colors.cyan; break;
case Colors.cyan: _swatch = Colors.teal; break;
case Colors.teal: _swatch = Colors.green; break;
case Colors.green: _swatch = Colors.lightGreen; break;
case Colors.lightGreen: _swatch = Colors.lime; break;
case Colors.lime: _swatch = Colors.yellow; break;
case Colors.yellow: _swatch = Colors.amber; break;
case Colors.amber: _swatch = Colors.orange; break;
case Colors.orange: _swatch = Colors.deepOrange; break;
case Colors.deepOrange: _swatch = Colors.brown; break;
case Colors.brown: _swatch = Colors.grey; break;
case Colors.grey: _swatch = Colors.blueGrey; break;
default: assert(false);
}
});
}
void _handleDirectionChange() {
setState(() {
_forward = !_forward;
});
}
Widget build(BuildContext context) {
return new Stack(
children: <Widget>[
new GestureDetector(
onScaleStart: _scaleEnabled ? _handleScaleStart : null,
onScaleUpdate: _scaleEnabled ? _handleScaleUpdate : null,
onTap: _tapEnabled ? _handleColorChange : null,
onDoubleTap: _doubleTapEnabled ? _handleScaleReset : null,
onLongPress: _longPressEnabled ? _handleDirectionChange : null,
child: new CustomPaint(
painter: new _GesturePainter(
zoom: _zoom,
offset: _offset,
swatch: _swatch,
forward: _forward,
scaleEnabled: _scaleEnabled,
tapEnabled: _tapEnabled,
doubleTapEnabled: _doubleTapEnabled,
longPressEnabled: _longPressEnabled
)
)
),
new Positioned(
bottom: 0.0,
left: 0.0,
child: new Card(
child: new Container(
padding: new EdgeDims.all(4.0),
child: new Column(
children: <Widget>[
new Row(
children: <Widget>[
new Checkbox(
value: _scaleEnabled,
onChanged: (bool value) { setState(() { _scaleEnabled = value; }); }
),
new Text('Scale'),
]
),
new Row(
children: <Widget>[
new Checkbox(
value: _tapEnabled,
onChanged: (bool value) { setState(() { _tapEnabled = value; }); }
),
new Text('Tap'),
]
),
new Row(
children: <Widget>[
new Checkbox(
value: _doubleTapEnabled,
onChanged: (bool value) { setState(() { _doubleTapEnabled = value; }); }
),
new Text('Double Tap'),
]
),
new Row(
children: <Widget>[
new Checkbox(
value: _longPressEnabled,
onChanged: (bool value) { setState(() { _longPressEnabled = value; }); }
),
new Text('Long Press'),
]
),
],
alignItems: FlexAlignItems.start
)
)
)
),
]
);
}
}
void main() {
runApp(new MaterialApp(
theme: new ThemeData.dark(),
routes: <String, RouteBuilder>{
'/': (RouteArguments args) {
return new Scaffold(
toolBar: new ToolBar(
center: new Text('Gestures Demo')),
body: new GestureDemo()
);
}
}
));
}