AutoScroll Text with pinch and zoom in flutter - flutter

Question

I'm new to flutter and I'm trying to implement a page where I want to show Text Widget with AutoScroll Also users can Zoom in and Zoom Out the text. I have implemented AutoScroll using the help of this link (AutoScroll Text). I have also added GestureDetector but It's not working as expected. Here is the complete source code which I have right now...
import 'dart:async';
import 'dart:ui';
import 'package:ffmpeg_demo/Utility/util.dart';
import 'package:flutter/material.dart';
class PDFViewer extends StatefulWidget {
final Function() onDismissTapped;
final String pdfText;
const PDFViewer(
{Key? key, required this.onDismissTapped, required this.pdfText})
: super(key: key);
#override
State<PDFViewer> createState() => _PDFViewerState();
}
class _PDFViewerState extends State<PDFViewer> {
double scrollSpeed = 1.0;
Function? onDismissTapped;
//https://stackoverflow.com/questions/57138772/how-to-autoscroll-text-in-flutter
final ScrollController _scrollController = ScrollController();
bool scroll = false;
int speedFactor = 100;
//For Scaling Text Area
//https://stackoverflow.com/questions/55440184/flutter-gesturedetector-how-to-pinch-in-out-or-zoom-in-out-text-using-two-finge
double _fontSize = 20;
final double _baseFontSize = 20;
double _fontScale = 1;
double _baseFontScale = 1;
double _scaleFactor = 1.0;
double _baseScaleFactor = 1.0;
bool _stopScrolling = false;
_scroll() {
double maxExtent = _scrollController.position.maxScrollExtent;
double distanceDifference = maxExtent - _scrollController.offset;
double durationDouble = distanceDifference / speedFactor;
int duration = durationDouble.toInt();
if (duration <= 0) {
duration = 1;
}
print(
"maxScrollExtent = $maxExtent and distanceDifference = $distanceDifference and durationDouble = $durationDouble");
_scrollController.animateTo(_scrollController.position.maxScrollExtent,
duration: Duration(seconds: duration), curve: Curves.linear);
}
_toggleScrolling() {
/* if (_stopScrolling) {
print("Stop scrolling flag value is $_stopScrolling");
return;
} */
setState(() {
scroll = !scroll;
});
if (scroll) {
_scroll();
} else {
_scrollController.animateTo(_scrollController.offset,
duration: const Duration(seconds: 1), curve: Curves.linear);
}
}
#override
void initState() {
// TODO: implement initState
super.initState();
Future.delayed(const Duration(seconds: 1), () {
_toggleScrolling();
});
}
#override
Widget build(BuildContext context) {
return Scaffold(
backgroundColor: Colors.transparent,
body: Container(
color: Colors.transparent,
child: BackdropFilter(
filter: ImageFilter.blur(sigmaX: 5.0, sigmaY: 5.0),
child: Container(
color: Colors.black.withOpacity(0.5),
child: Stack(
children: [
Padding(
padding: const EdgeInsets.fromLTRB(10, 50, 10, 100),
child: NotificationListener(
onNotification: (notif) {
if (notif is ScrollEndNotification && scroll) {
Timer(const Duration(seconds: 1), () {
_scroll();
});
}
return true;
},
child: SingleChildScrollView(
controller: _scrollController,
scrollDirection: Axis.vertical,
padding: const EdgeInsets.all(20),
child: DefaultTextStyle(
style: const TextStyle(color: Colors.white),
child: GestureDetector(
onScaleStart: (ScaleStartDetails scaleStartDetails) {
setState(() {
//_stopScrolling = true;
_toggleScrolling();
});
//_baseScaleFactor = _scaleFactor;
_baseFontScale = _fontScale;
print("base scale factor = $_baseFontScale");
},
onScaleUpdate:
(ScaleUpdateDetails scaleUpdateDetails) {
// don't update the UI if the scale didn't change
/* if (scaleUpdateDetails.scale == 1.0) {
debugPrint("Scale is 1.0 returning");
setState(() {
_stopScrolling = false;
_toggleScrolling();
});
return;
} */
/* _scaleFactor =
_baseScaleFactor * scaleUpdateDetails.scale;
print("Final scale factor = $_scaleFactor");
if (_scaleFactor < 1.0) {
_scaleFactor = 1.0;
}
print("New Final scale factor = $_scaleFactor"); */
//setState(() {
_fontScale =
(_baseFontScale * scaleUpdateDetails.scale)
.clamp(0.5, 5.0);
_fontSize = _fontScale * _baseFontSize;
debugPrint("New Final font size = $_fontSize");
if (_fontSize < 20) {
_fontSize = 20;
}
//});
setState(() {
//_toggleScrolling();
_stopScrolling = false;
_toggleScrolling();
});
},
child: Text(
widget.pdfText,
/* textScaleFactor:
(_scaleFactor <= 0.1) ? 1.0 : _scaleFactor, */
style: TextStyle(
fontSize: (_fontSize < 20) ? 20 : _fontSize),
),
),
),
),
),
),
Positioned(
bottom: 0,
child: Container(
height: 100,
width: deviceWidth(context),
color: Colors.black.withAlpha(50),
child: Stack(
children: [
Positioned(
bottom: 0,
width: deviceWidth(context),
child: Center(
child: TextButton(
child: const Text(
"Dismiss",
style: TextStyle(color: Colors.white),
),
onPressed: () => widget.onDismissTapped(),
),
),
),
Positioned(
top: 0,
width: deviceWidth(context),
child: Container(
height: 50,
width: deviceWidth(context),
child: _buildSlider(context)),
),
],
),
),
),
],
),
),
),
),
);
}
Widget _buildSlider(BuildContext context) {
return Container(
width: deviceWidth(context),
child: SliderTheme(
data: SliderThemeData(
activeTrackColor: Colors.brown[700],
inactiveTrackColor: Colors.brown[300],
inactiveTickMarkColor: Colors.transparent,
activeTickMarkColor: Colors.transparent),
child: Slider(
divisions: 100,
min: 0,
max: 100,
value: speedFactor.toDouble(),
onChanged: (double value) {
setState(() {
//scrollSpeed = value;
_toggleScrolling();
});
speedFactor = value.toInt();
if (speedFactor == 0) {
speedFactor = 1;
}
Future.delayed(const Duration(seconds: 1), () {
setState(() {
//scrollSpeed = value;
_toggleScrolling();
});
});
}),
),
);
}
}