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@happyharis
Created December 3, 2018 05:01
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import 'package:flutter/material.dart';
import 'package:flutter/gestures.dart';
void main() => runApp(new MyApp());
class MyApp extends StatelessWidget {
@override
Widget build(BuildContext context) {
return new MaterialApp(
theme: new ThemeData(
primarySwatch: Colors.blue,
),
home: new Scaffold(
appBar: new AppBar(
title: new Text('Draggable Scroll Bar Demo'),
),
//DraggableScrollbar builds Stack with provided Scrollable List of Grid
body: new DraggableScrollbar(
child: _buildGrid(),
),
),
);
}
Widget _buildGrid() {
return GridView.builder(
gridDelegate: SliverGridDelegateWithFixedCrossAxisCount(
crossAxisCount: 5,
),
padding: EdgeInsets.zero,
itemCount: 1000,
itemBuilder: (context, index) {
return Container(
alignment: Alignment.center,
margin: EdgeInsets.all(2.0),
color: Colors.grey[300],
);
},
);
}
}
class DraggableScrollbar extends StatefulWidget {
const DraggableScrollbar({this.child});
final Widget child;
@override
_DraggableScrollbarState createState() => new _DraggableScrollbarState();
}
class _DraggableScrollbarState extends State<DraggableScrollbar>
with TickerProviderStateMixin {
//this counts offset for scroll thumb for Vertical axis
double _barOffset;
// controller for the thing
AnimationController animationController;
Animation<double> animation;
@override
void initState() {
super.initState();
animationController =
AnimationController(vsync: this, duration: Duration(seconds: 1));
_barOffset = 300.0;
}
void _onVerticalDragUpdate(DragUpdateDetails details) {
setState(() {
_barOffset += details.delta.dy;
});
}
void _animateSelectorBack() {
if (mounted) {
setState(() {
_barOffset = animation.value;
});
}
}
void _verticalGoesBack(DragEndDetails details) {
animationController.reset();
animation = Tween<double>(begin: _barOffset, end: 300.0)
.animate(animationController)
..addListener(_animateSelectorBack)
..addStatusListener((status) {
if (status == AnimationStatus.completed) {
animationController.removeListener(_animateSelectorBack);
}
});
animationController.forward();
}
@override
Widget build(BuildContext context) {
return new Stack(children: <Widget>[
widget.child,
GestureDetector(
onVerticalDragUpdate: _onVerticalDragUpdate,
onVerticalDragEnd: _verticalGoesBack,
child: Container(
alignment: Alignment.topRight,
margin: EdgeInsets.only(top: _barOffset),
child: _buildScrollThumb())),
]);
}
Widget _buildScrollThumb() {
return new Container(
height: 40.0,
width: 20.0,
color: Colors.blue,
);
}
@override
void dispose() {
super.dispose();
animationController.dispose();
}
}
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