Flutter: change widget scale when widget dragged - flutter

Question

I am trying to change the widget size (scale) when I drag the widget up. I am using the GestureDetector and onPanUpdate method and Now I want to by Matrix4.identity to change the size of the widget:
return GestureDetector(
onPanUpdate: (details) {
_position += details.delta;
setState(() {});
},
child: Stack(
children: [
SizedBox(
child: LayoutBuilder(builder: (context, constraints) {
final milliSeconds = _isDragging ? 0 : 400;
final center = constraints.smallest.center(Offset.zero);
final scaledMatrix = Matrix4.identity();
// ..translate(center.dx, center.dy)
// ..scale(1.0, 0.5)
// ..translate(-center.dx, -center.dy);
return AnimatedContainer(
curve: Curves.easeInOut,
duration: Duration(milliseconds: milliSeconds),
transform: scaledMatrix
..translate(_position.dx, _position.dy),
child: widget.widgets[0]);
}),
),
],
));
Now when the widget is dragged I change the position but how can I change the widget scale ?

Answer 1

You can use Matrix4.identity()..scale api to achieve this.
import 'package:flutter/material.dart';
void main() => runApp(MaterialApp(
home: Scaffold(appBar: AppBar(), body: _Drag()),
));
class _Drag extends StatefulWidget {
#override
_DragState createState() => _DragState();
}
class _DragState extends State<_Drag> with SingleTickerProviderStateMixin {
bool shouldScaleDown = true; // change value when needed
double _top = 300; // distance to top
double _left = 150; // distance to left
double scale = 1;
#override
Widget build(BuildContext context) {
return Stack(
children: <Widget>[
Positioned(
top: _top,
left: _left,
child: GestureDetector(
onPanDown: (DragDownDetails e) {
print("fingure down: ${e.globalPosition}");
},
onPanUpdate: (DragUpdateDetails e) {
setState(() {
_left += e.delta.dx;
_top += e.delta.dy;
if (e.delta.dy > 0) {
scale = scale - 0.01;
}
if (e.delta.dy < 0) {
scale = scale + 0.01;
}
});
},
onPanEnd: (DragEndDetails e) {
print("fingure away from screen");
print(e.velocity);
},
child: AnimatedContainer(
color: Colors.blueAccent,
width: 100,
height: 100,
duration: Duration(milliseconds: 300),
transform: Matrix4.identity()..scale(scale, scale),
child: Container(),
),
),
)
],
);
}
}