dev/manual_tests/material_arc.dart - mirrors/flutter - Git at Google

 // Copyright 2016 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 'dart:async';

 import 'package:flutter/gestures.dart';
 import 'package:flutter/material.dart';

 enum _DragTarget {
   start,
   end
 }

 // How close a drag's start position must be to the target point. This is
 // a distance squared.
 const double _kTargetSlop = 2500.0;

 // Used by the Painter classes.
 const double _kPointRadius = 6.0;

 class _DragHandler extends Drag {
   _DragHandler(this.onUpdate, this.onCancel, this.onEnd);

   final GestureDragUpdateCallback onUpdate;
   final GestureDragCancelCallback onCancel;
   final GestureDragEndCallback onEnd;

   @override
   void update(DragUpdateDetails details)  {
     onUpdate(details);
   }

   @override
   void cancel()  {
     onCancel();
   }

   @override
   void end(DragEndDetails details)  {
     onEnd(details);
   }
 }

 class _IgnoreDrag extends Drag {
 }

 class _PointDemoPainter extends CustomPainter {
   _PointDemoPainter({
     Animation<double> repaint,
     this.arc
   }) : _repaint = repaint, super(repaint: repaint);

   final MaterialPointArcTween arc;
   Animation<double> _repaint;

   void drawPoint(Canvas canvas, Point point, Color color) {
     final Paint paint = new Paint()
       ..color = color.withOpacity(0.25)
       ..style = PaintingStyle.fill;
     canvas.drawCircle(point, _kPointRadius, paint);
     paint
       ..color = color
       ..style = PaintingStyle.stroke
       ..strokeWidth = 2.0;
     canvas.drawCircle(point, _kPointRadius + 1.0, paint);
   }

   @override
   void paint(Canvas canvas, Size size) {
     final Paint paint = new Paint();

     if (arc.center != null)
       drawPoint(canvas, arc.center, Colors.grey[400]);

     paint
       ..isAntiAlias = false // Work-around for github.com/flutter/flutter/issues/5720
       ..color = Colors.green[500].withOpacity(0.25)
       ..strokeWidth = 4.0
       ..style = PaintingStyle.stroke;
     if (arc.center != null && arc.radius != null)
       canvas.drawCircle(arc.center, arc.radius, paint);
     else
       canvas.drawLine(arc.begin, arc.end, paint);

     drawPoint(canvas, arc.begin, Colors.green[500]);
     drawPoint(canvas, arc.end, Colors.red[500]);

     paint
       ..color = Colors.green[500]
       ..style = PaintingStyle.fill;
     canvas.drawCircle(arc.lerp(_repaint.value), _kPointRadius, paint);
   }

   @override
   bool hitTest(Point position) {
     return (arc.begin - position).distanceSquared < _kTargetSlop
         || (arc.end - position).distanceSquared < _kTargetSlop;
   }

   @override
   bool shouldRepaint(_PointDemoPainter oldPainter) => arc != oldPainter.arc;
 }

 class _PointDemo extends StatefulWidget {
   _PointDemo({ Key key, this.controller }) : super(key: key);

   final AnimationController controller;

   @override
   _PointDemoState createState() => new _PointDemoState();
 }

 class _PointDemoState extends State<_PointDemo> {
   final GlobalKey _painterKey = new GlobalKey();

   CurvedAnimation _animation;
   _DragTarget _dragTarget;
   Size _screenSize;
   Point _begin;
   Point _end;

   @override
   void initState() {
     super.initState();
     _animation = new CurvedAnimation(parent: config.controller, curve: Curves.fastOutSlowIn);
   }

   @override
   void dispose() {
     config.controller.value = 0.0;
     super.dispose();
   }

   Drag _handleOnStart(Point position) {
     // TODO(hansmuller): allow the user to drag both points at the same time.
     if (_dragTarget != null)
       return new _IgnoreDrag();

     final RenderBox box = _painterKey.currentContext.findRenderObject();
     final double startOffset = (box.localToGlobal(_begin) - position).distanceSquared;
     final double endOffset = (box.localToGlobal(_end) - position).distanceSquared;
     setState(() {
       if (startOffset < endOffset && startOffset < _kTargetSlop)
         _dragTarget = _DragTarget.start;
       else if (endOffset < _kTargetSlop)
         _dragTarget = _DragTarget.end;
       else
         _dragTarget = null;
     });

     return new _DragHandler(_handleDragUpdate, _handleDragCancel, _handleDragEnd);
   }

   void _handleDragUpdate(DragUpdateDetails details)  {
     switch (_dragTarget) {
       case _DragTarget.start:
         setState(() {
           _begin = _begin + details.delta;
         });
         break;
       case _DragTarget.end:
         setState(() {
           _end = _end + details.delta;
         });
         break;
     }
   }

   void _handleDragCancel()  {
     _dragTarget = null;
     config.controller.value = 0.0;
   }

   void _handleDragEnd(DragEndDetails details)  {
     _dragTarget = null;
   }

   @override
   Widget build(BuildContext context) {
     final Size screenSize = MediaQuery.of(context).size;
     if (_screenSize == null || _screenSize != screenSize) {
       _screenSize = screenSize;
       _begin = new Point(screenSize.width * 0.5, screenSize.height * 0.2);
       _end = new Point(screenSize.width * 0.1, screenSize.height * 0.4);
     }

     final MaterialPointArcTween arc = new MaterialPointArcTween(begin: _begin, end: _end);
     return new RawGestureDetector(
       behavior: _dragTarget == null ? HitTestBehavior.deferToChild : HitTestBehavior.opaque,
       gestures: <Type, GestureRecognizerFactory>{
         ImmediateMultiDragGestureRecognizer: (ImmediateMultiDragGestureRecognizer recognizer) { // ignore: map_value_type_not_assignable, https://github.com/flutter/flutter/issues/5771
           return (recognizer ??= new ImmediateMultiDragGestureRecognizer())
             ..onStart = _handleOnStart;
         }
       },
       child: new ClipRect(
         child: new CustomPaint(
           key: _painterKey,
           foregroundPainter: new _PointDemoPainter(
             repaint: _animation,
             arc: arc
           ),
           // Watch out: if this IgnorePointer is left out, then gestures that
           // fail _PointDemoPainter.hitTest() will still be recognized because
           // they do overlap this child, which is as big as the CustomPaint.
           child: new IgnorePointer(
             child: new Padding(
               padding: const EdgeInsets.all(16.0),
               child: new Text(
                 "Tap the refresh button to run the animation. Drag the green "
                 "and red points to change the animation's path.",
                 style: Theme.of(context).textTheme.caption.copyWith(fontSize: 16.0)
               )
             )
           )
         )
       )
     );
   }
 }

 class _RectangleDemoPainter extends CustomPainter {
   _RectangleDemoPainter({
     Animation<double> repaint,
     this.arc
   }) : _repaint = repaint, super(repaint: repaint);

   final MaterialRectArcTween arc;
   Animation<double> _repaint;

   void drawPoint(Canvas canvas, Point p, Color color) {
     final Paint paint = new Paint()
       ..color = color.withOpacity(0.25)
       ..style = PaintingStyle.fill;
     canvas.drawCircle(p, _kPointRadius, paint);
     paint
       ..color = color
       ..style = PaintingStyle.stroke
       ..strokeWidth = 2.0;
     canvas.drawCircle(p, _kPointRadius + 1.0, paint);
   }

   void drawRect(Canvas canvas, Rect rect, Color color) {
     final Paint paint = new Paint()
       ..color = color.withOpacity(0.25)
       ..strokeWidth = 4.0
       ..style = PaintingStyle.stroke;
     canvas.drawRect(rect, paint);
     drawPoint(canvas, rect.center, color);
   }

   @override
   void paint(Canvas canvas, Size size) {
     drawRect(canvas, arc.begin, Colors.green[500]);
     drawRect(canvas, arc.end, Colors.red[500]);
     drawRect(canvas, arc.lerp(_repaint.value), Colors.blue[500]);
   }

   @override
   bool hitTest(Point position) {
     return (arc.begin.center - position).distanceSquared < _kTargetSlop
         || (arc.end.center - position).distanceSquared < _kTargetSlop;
   }

   @override
   bool shouldRepaint(_RectangleDemoPainter oldPainter) => arc != oldPainter.arc;
 }

 class _RectangleDemo extends StatefulWidget {
   _RectangleDemo({ Key key, this.controller }) : super(key: key);

   final AnimationController controller;

   @override
   _RectangleDemoState createState() => new _RectangleDemoState();
 }

 class _RectangleDemoState extends State<_RectangleDemo> {
   final GlobalKey _painterKey = new GlobalKey();

   CurvedAnimation _animation;
   _DragTarget _dragTarget;
   Size _screenSize;
   Rect _begin;
   Rect _end;

   @override
   void initState() {
     super.initState();
     _animation = new CurvedAnimation(parent: config.controller, curve: Curves.fastOutSlowIn);
   }

   @override
   void dispose() {
     config.controller.value = 0.0;
     super.dispose();
   }

   Drag _handleOnStart(Point position) {
     // TODO(hansmuller): allow the user to drag both points at the same time.
     if (_dragTarget != null)
       return new _IgnoreDrag();

     final RenderBox box = _painterKey.currentContext.findRenderObject();
     final double startOffset = (box.localToGlobal(_begin.center) - position).distanceSquared;
     final double endOffset = (box.localToGlobal(_end.center) - position).distanceSquared;
     setState(() {
       if (startOffset < endOffset && startOffset < _kTargetSlop)
         _dragTarget = _DragTarget.start;
       else if (endOffset < _kTargetSlop)
         _dragTarget = _DragTarget.end;
       else
         _dragTarget = null;
     });
     return new _DragHandler(_handleDragUpdate, _handleDragCancel, _handleDragEnd);
   }

   void _handleDragUpdate(DragUpdateDetails details)  {
     switch (_dragTarget) {
       case _DragTarget.start:
         setState(() {
           _begin = _begin.shift(details.delta);
         });
         break;
       case _DragTarget.end:
         setState(() {
           _end = _end.shift(details.delta);
         });
         break;
     }
   }

   void _handleDragCancel()  {
     _dragTarget = null;
     config.controller.value = 0.0;
   }

   void _handleDragEnd(DragEndDetails details)  {
     _dragTarget = null;
   }

   @override
   Widget build(BuildContext context) {
     final Size screenSize = MediaQuery.of(context).size;
     if (_screenSize == null || _screenSize != screenSize) {
       _screenSize = screenSize;
       _begin = new Rect.fromLTWH(
         screenSize.width * 0.5, screenSize.height * 0.2,
         screenSize.width * 0.4, screenSize.height * 0.2
       );
       _end = new Rect.fromLTWH(
         screenSize.width * 0.1, screenSize.height * 0.4,
         screenSize.width * 0.3, screenSize.height * 0.3
       );
     }

     final MaterialRectArcTween arc = new MaterialRectArcTween(begin: _begin, end: _end);
     return new RawGestureDetector(
       behavior: _dragTarget == null ? HitTestBehavior.deferToChild : HitTestBehavior.opaque,
       gestures: <Type, GestureRecognizerFactory>{
         ImmediateMultiDragGestureRecognizer: (ImmediateMultiDragGestureRecognizer recognizer) { // ignore: map_value_type_not_assignable, https://github.com/flutter/flutter/issues/5771
           return (recognizer ??= new ImmediateMultiDragGestureRecognizer())
             ..onStart = _handleOnStart;
         }
       },
       child: new ClipRect(
         child: new CustomPaint(
           key: _painterKey,
           foregroundPainter: new _RectangleDemoPainter(
             repaint: _animation,
             arc: arc
           ),
           // Watch out: if this IgnorePointer is left out, then gestures that
           // fail _RectDemoPainter.hitTest() will still be recognized because
           // they do overlap this child, which is as big as the CustomPaint.
           child: new IgnorePointer(
             child: new Padding(
               padding: const EdgeInsets.all(16.0),
               child: new Text(
                 "Tap the refresh button to run the animation. Drag the rectangles "
                 "to change the animation's path.",
                 style: Theme.of(context).textTheme.caption.copyWith(fontSize: 16.0)
               )
             )
           )
         )
       )
     );
   }
 }

 typedef Widget _DemoBuilder(_ArcDemo demo);

 class _ArcDemo {
   _ArcDemo(String _title, this.builder, TickerProvider vsync)
     : title = _title,
       controller = new AnimationController(duration: const Duration(milliseconds: 500), vsync: vsync),
       key = new GlobalKey(debugLabel: _title);

   final String title;
   final _DemoBuilder builder;
   final AnimationController controller;
   final GlobalKey key;
 }

 class AnimationDemo extends StatefulWidget {
   AnimationDemo({ Key key }) : super(key: key);

   @override
   _AnimationDemoState createState() => new _AnimationDemoState();
 }

 class _AnimationDemoState extends State<AnimationDemo> with TickerProviderStateMixin {
   static final GlobalKey<TabBarSelectionState<_ArcDemo>> _tabsKey = new GlobalKey<TabBarSelectionState<_ArcDemo>>();

   List<_ArcDemo> _allDemos;

   @override
   void initState() {
     super.initState();
     _allDemos = <_ArcDemo>[
       new _ArcDemo('POINT', (_ArcDemo demo) {
         return new _PointDemo(
           key: demo.key,
           controller: demo.controller
         );
       }, this),
       new _ArcDemo('RECTANGLE', (_ArcDemo demo) {
         return new _RectangleDemo(
           key: demo.key,
           controller: demo.controller
         );
       }, this),
     ];
   }

   Future<Null> _play() async {
     _ArcDemo demo = _tabsKey.currentState.value;
     await demo.controller.forward();
     if (demo.key.currentState != null && demo.key.currentState.mounted)
       demo.controller.reverse();
   }

   @override
   Widget build(BuildContext context) {
     return new TabBarSelection<_ArcDemo>(
       key: _tabsKey,
       values: _allDemos,
       child: new Scaffold(
         appBar: new AppBar(
           title: new Text('Animation'),
           bottom: new TabBar<_ArcDemo>(
             labels: new Map<_ArcDemo, TabLabel>.fromIterable(_allDemos, value: (_ArcDemo demo) {
               return new TabLabel(text: demo.title);
             })
           )
         ),
         floatingActionButton: new FloatingActionButton(
           onPressed: _play,
           child: new Icon(Icons.refresh)
         ),
         body: new TabBarView<_ArcDemo>(
           children: _allDemos.map((_ArcDemo demo) => demo.builder(demo)).toList()
         )
       )
     );
   }
 }

 void main() {
   runApp(new MaterialApp(
     home: new AnimationDemo()
   ));
 }
	// Copyright 2016 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 'dart:async';

	import 'package:flutter/gestures.dart';
	import 'package:flutter/material.dart';

	enum _DragTarget {
	start,
	end
	}

	// How close a drag's start position must be to the target point. This is
	// a distance squared.
	const double _kTargetSlop = 2500.0;

	// Used by the Painter classes.
	const double _kPointRadius = 6.0;

	class _DragHandler extends Drag {
	_DragHandler(this.onUpdate, this.onCancel, this.onEnd);

	final GestureDragUpdateCallback onUpdate;
	final GestureDragCancelCallback onCancel;
	final GestureDragEndCallback onEnd;

	@override
	void update(DragUpdateDetails details) {
	onUpdate(details);
	}

	@override
	void cancel() {
	onCancel();
	}

	@override
	void end(DragEndDetails details) {
	onEnd(details);
	}
	}

	class _IgnoreDrag extends Drag {
	}

	class _PointDemoPainter extends CustomPainter {
	_PointDemoPainter({
	Animation<double> repaint,
	this.arc
	}) : _repaint = repaint, super(repaint: repaint);

	final MaterialPointArcTween arc;
	Animation<double> _repaint;

	void drawPoint(Canvas canvas, Point point, Color color) {
	final Paint paint = new Paint()
	..color = color.withOpacity(0.25)
	..style = PaintingStyle.fill;
	canvas.drawCircle(point, _kPointRadius, paint);
	paint
	..color = color
	..style = PaintingStyle.stroke
	..strokeWidth = 2.0;
	canvas.drawCircle(point, _kPointRadius + 1.0, paint);
	}

	@override
	void paint(Canvas canvas, Size size) {
	final Paint paint = new Paint();

	if (arc.center != null)
	drawPoint(canvas, arc.center, Colors.grey[400]);

	paint
	..isAntiAlias = false // Work-around for github.com/flutter/flutter/issues/5720
	..color = Colors.green[500].withOpacity(0.25)
	..strokeWidth = 4.0
	..style = PaintingStyle.stroke;
	if (arc.center != null && arc.radius != null)
	canvas.drawCircle(arc.center, arc.radius, paint);
	else
	canvas.drawLine(arc.begin, arc.end, paint);

	drawPoint(canvas, arc.begin, Colors.green[500]);
	drawPoint(canvas, arc.end, Colors.red[500]);

	paint
	..color = Colors.green[500]
	..style = PaintingStyle.fill;
	canvas.drawCircle(arc.lerp(_repaint.value), _kPointRadius, paint);
	}

	@override
	bool hitTest(Point position) {
	return (arc.begin - position).distanceSquared < _kTargetSlop
	\|\| (arc.end - position).distanceSquared < _kTargetSlop;
	}

	@override
	bool shouldRepaint(_PointDemoPainter oldPainter) => arc != oldPainter.arc;
	}

	class _PointDemo extends StatefulWidget {
	_PointDemo({ Key key, this.controller }) : super(key: key);

	final AnimationController controller;

	@override
	_PointDemoState createState() => new _PointDemoState();
	}

	class _PointDemoState extends State<_PointDemo> {
	final GlobalKey _painterKey = new GlobalKey();

	CurvedAnimation _animation;
	_DragTarget _dragTarget;
	Size _screenSize;
	Point _begin;
	Point _end;

	@override
	void initState() {
	super.initState();
	_animation = new CurvedAnimation(parent: config.controller, curve: Curves.fastOutSlowIn);
	}

	@override
	void dispose() {
	config.controller.value = 0.0;
	super.dispose();
	}

	Drag _handleOnStart(Point position) {
	// TODO(hansmuller): allow the user to drag both points at the same time.
	if (_dragTarget != null)
	return new _IgnoreDrag();

	final RenderBox box = _painterKey.currentContext.findRenderObject();
	final double startOffset = (box.localToGlobal(_begin) - position).distanceSquared;
	final double endOffset = (box.localToGlobal(_end) - position).distanceSquared;
	setState(() {
	if (startOffset < endOffset && startOffset < _kTargetSlop)
	_dragTarget = _DragTarget.start;
	else if (endOffset < _kTargetSlop)
	_dragTarget = _DragTarget.end;
	else
	_dragTarget = null;
	});

	return new _DragHandler(_handleDragUpdate, _handleDragCancel, _handleDragEnd);
	}

	void _handleDragUpdate(DragUpdateDetails details) {
	switch (_dragTarget) {
	case _DragTarget.start:
	setState(() {
	_begin = _begin + details.delta;
	});
	break;
	case _DragTarget.end:
	setState(() {
	_end = _end + details.delta;
	});
	break;
	}
	}

	void _handleDragCancel() {
	_dragTarget = null;
	config.controller.value = 0.0;
	}

	void _handleDragEnd(DragEndDetails details) {
	_dragTarget = null;
	}

	@override
	Widget build(BuildContext context) {
	final Size screenSize = MediaQuery.of(context).size;
	if (_screenSize == null \|\| _screenSize != screenSize) {
	_screenSize = screenSize;
	_begin = new Point(screenSize.width * 0.5, screenSize.height * 0.2);
	_end = new Point(screenSize.width * 0.1, screenSize.height * 0.4);
	}

	final MaterialPointArcTween arc = new MaterialPointArcTween(begin: _begin, end: _end);
	return new RawGestureDetector(
	behavior: _dragTarget == null ? HitTestBehavior.deferToChild : HitTestBehavior.opaque,
	gestures: <Type, GestureRecognizerFactory>{
	ImmediateMultiDragGestureRecognizer: (ImmediateMultiDragGestureRecognizer recognizer) { // ignore: map_value_type_not_assignable, https://github.com/flutter/flutter/issues/5771
	return (recognizer ??= new ImmediateMultiDragGestureRecognizer())
	..onStart = _handleOnStart;
	}
	},
	child: new ClipRect(
	child: new CustomPaint(
	key: _painterKey,
	foregroundPainter: new _PointDemoPainter(
	repaint: _animation,
	arc: arc
	),
	// Watch out: if this IgnorePointer is left out, then gestures that
	// fail _PointDemoPainter.hitTest() will still be recognized because
	// they do overlap this child, which is as big as the CustomPaint.
	child: new IgnorePointer(
	child: new Padding(
	padding: const EdgeInsets.all(16.0),
	child: new Text(
	"Tap the refresh button to run the animation. Drag the green "
	"and red points to change the animation's path.",
	style: Theme.of(context).textTheme.caption.copyWith(fontSize: 16.0)
	)
	)
	)
	)
	)
	);
	}
	}

	class _RectangleDemoPainter extends CustomPainter {
	_RectangleDemoPainter({
	Animation<double> repaint,
	this.arc
	}) : _repaint = repaint, super(repaint: repaint);

	final MaterialRectArcTween arc;
	Animation<double> _repaint;

	void drawPoint(Canvas canvas, Point p, Color color) {
	final Paint paint = new Paint()
	..color = color.withOpacity(0.25)
	..style = PaintingStyle.fill;
	canvas.drawCircle(p, _kPointRadius, paint);
	paint
	..color = color
	..style = PaintingStyle.stroke
	..strokeWidth = 2.0;
	canvas.drawCircle(p, _kPointRadius + 1.0, paint);
	}

	void drawRect(Canvas canvas, Rect rect, Color color) {
	final Paint paint = new Paint()
	..color = color.withOpacity(0.25)
	..strokeWidth = 4.0
	..style = PaintingStyle.stroke;
	canvas.drawRect(rect, paint);
	drawPoint(canvas, rect.center, color);
	}

	@override
	void paint(Canvas canvas, Size size) {
	drawRect(canvas, arc.begin, Colors.green[500]);
	drawRect(canvas, arc.end, Colors.red[500]);
	drawRect(canvas, arc.lerp(_repaint.value), Colors.blue[500]);
	}

	@override
	bool hitTest(Point position) {
	return (arc.begin.center - position).distanceSquared < _kTargetSlop
	\|\| (arc.end.center - position).distanceSquared < _kTargetSlop;
	}

	@override
	bool shouldRepaint(_RectangleDemoPainter oldPainter) => arc != oldPainter.arc;
	}

	class _RectangleDemo extends StatefulWidget {
	_RectangleDemo({ Key key, this.controller }) : super(key: key);

	final AnimationController controller;

	@override
	_RectangleDemoState createState() => new _RectangleDemoState();
	}

	class _RectangleDemoState extends State<_RectangleDemo> {
	final GlobalKey _painterKey = new GlobalKey();

	CurvedAnimation _animation;
	_DragTarget _dragTarget;
	Size _screenSize;
	Rect _begin;
	Rect _end;

	@override
	void initState() {
	super.initState();
	_animation = new CurvedAnimation(parent: config.controller, curve: Curves.fastOutSlowIn);
	}

	@override
	void dispose() {
	config.controller.value = 0.0;
	super.dispose();
	}

	Drag _handleOnStart(Point position) {
	// TODO(hansmuller): allow the user to drag both points at the same time.
	if (_dragTarget != null)
	return new _IgnoreDrag();

	final RenderBox box = _painterKey.currentContext.findRenderObject();
	final double startOffset = (box.localToGlobal(_begin.center) - position).distanceSquared;
	final double endOffset = (box.localToGlobal(_end.center) - position).distanceSquared;
	setState(() {
	if (startOffset < endOffset && startOffset < _kTargetSlop)
	_dragTarget = _DragTarget.start;
	else if (endOffset < _kTargetSlop)
	_dragTarget = _DragTarget.end;
	else
	_dragTarget = null;
	});
	return new _DragHandler(_handleDragUpdate, _handleDragCancel, _handleDragEnd);
	}

	void _handleDragUpdate(DragUpdateDetails details) {
	switch (_dragTarget) {
	case _DragTarget.start:
	setState(() {
	_begin = _begin.shift(details.delta);
	});
	break;
	case _DragTarget.end:
	setState(() {
	_end = _end.shift(details.delta);
	});
	break;
	}
	}

	void _handleDragCancel() {
	_dragTarget = null;
	config.controller.value = 0.0;
	}

	void _handleDragEnd(DragEndDetails details) {
	_dragTarget = null;
	}

	@override
	Widget build(BuildContext context) {
	final Size screenSize = MediaQuery.of(context).size;
	if (_screenSize == null \|\| _screenSize != screenSize) {
	_screenSize = screenSize;
	_begin = new Rect.fromLTWH(
	screenSize.width * 0.5, screenSize.height * 0.2,
	screenSize.width * 0.4, screenSize.height * 0.2
	);
	_end = new Rect.fromLTWH(
	screenSize.width * 0.1, screenSize.height * 0.4,
	screenSize.width * 0.3, screenSize.height * 0.3
	);
	}

	final MaterialRectArcTween arc = new MaterialRectArcTween(begin: _begin, end: _end);
	return new RawGestureDetector(
	behavior: _dragTarget == null ? HitTestBehavior.deferToChild : HitTestBehavior.opaque,
	gestures: <Type, GestureRecognizerFactory>{
	ImmediateMultiDragGestureRecognizer: (ImmediateMultiDragGestureRecognizer recognizer) { // ignore: map_value_type_not_assignable, https://github.com/flutter/flutter/issues/5771
	return (recognizer ??= new ImmediateMultiDragGestureRecognizer())
	..onStart = _handleOnStart;
	}
	},
	child: new ClipRect(
	child: new CustomPaint(
	key: _painterKey,
	foregroundPainter: new _RectangleDemoPainter(
	repaint: _animation,
	arc: arc
	),
	// Watch out: if this IgnorePointer is left out, then gestures that
	// fail _RectDemoPainter.hitTest() will still be recognized because
	// they do overlap this child, which is as big as the CustomPaint.
	child: new IgnorePointer(
	child: new Padding(
	padding: const EdgeInsets.all(16.0),
	child: new Text(
	"Tap the refresh button to run the animation. Drag the rectangles "
	"to change the animation's path.",
	style: Theme.of(context).textTheme.caption.copyWith(fontSize: 16.0)
	)
	)
	)
	)
	)
	);
	}
	}

	typedef Widget _DemoBuilder(_ArcDemo demo);

	class _ArcDemo {
	_ArcDemo(String _title, this.builder, TickerProvider vsync)
	: title = _title,
	controller = new AnimationController(duration: const Duration(milliseconds: 500), vsync: vsync),
	key = new GlobalKey(debugLabel: _title);

	final String title;
	final _DemoBuilder builder;
	final AnimationController controller;
	final GlobalKey key;
	}

	class AnimationDemo extends StatefulWidget {
	AnimationDemo({ Key key }) : super(key: key);

	@override
	_AnimationDemoState createState() => new _AnimationDemoState();
	}

	class _AnimationDemoState extends State<AnimationDemo> with TickerProviderStateMixin {
	static final GlobalKey<TabBarSelectionState<_ArcDemo>> _tabsKey = new GlobalKey<TabBarSelectionState<_ArcDemo>>();

	List<_ArcDemo> _allDemos;

	@override
	void initState() {
	super.initState();
	_allDemos = <_ArcDemo>[
	new _ArcDemo('POINT', (_ArcDemo demo) {
	return new _PointDemo(
	key: demo.key,
	controller: demo.controller
	);
	}, this),
	new _ArcDemo('RECTANGLE', (_ArcDemo demo) {
	return new _RectangleDemo(
	key: demo.key,
	controller: demo.controller
	);
	}, this),
	];
	}

	Future<Null> _play() async {
	_ArcDemo demo = _tabsKey.currentState.value;
	await demo.controller.forward();
	if (demo.key.currentState != null && demo.key.currentState.mounted)
	demo.controller.reverse();
	}

	@override
	Widget build(BuildContext context) {
	return new TabBarSelection<_ArcDemo>(
	key: _tabsKey,
	values: _allDemos,
	child: new Scaffold(
	appBar: new AppBar(
	title: new Text('Animation'),
	bottom: new TabBar<_ArcDemo>(
	labels: new Map<_ArcDemo, TabLabel>.fromIterable(_allDemos, value: (_ArcDemo demo) {
	return new TabLabel(text: demo.title);
	})
	)
	),
	floatingActionButton: new FloatingActionButton(
	onPressed: _play,
	child: new Icon(Icons.refresh)
	),
	body: new TabBarView<_ArcDemo>(
	children: _allDemos.map((_ArcDemo demo) => demo.builder(demo)).toList()
	)
	)
	);
	}
	}

	void main() {
	runApp(new MaterialApp(
	home: new AnimationDemo()
	));
	}