getting the old scroll offset using the Package flutter_webview_plugin - flutter

Question

i am trying to integrate a Webview in a Test app using the Package flutter_webview_plugin
my goal is to hide a bottomNavigationBar when the User scroll up in the Webview and show it, when the user scroll down.
in the mentioned Package there is a listner to listen to vertical Schroll changes :
final flutterWebviewPlugin = new FlutterWebviewPlugin();
flutterWebviewPlugin.onScrollYChanged.listen((double offsetY) { // latest offset value in vertical scroll
// compare vertical scroll changes here with old value
});
the offsetY value, is the current value, but how can't i get the old value, to compare it with the new value ? any idea ?

Answer 1

ok, i have implemented a solution to this.
i have defined a variable oldOffset = 0.0 and in the method trackOffsetChange i checked if oldOffset value smaller than the currentOffset value. if it's the case then oldOffset get the value of currentOffset and with setState i rebuild the widget to hide the BottomNavBar, else show the BottomNavBar.
here is the whole code of the test App, if someone new like me, is interested to see the source code:
import 'package:flutter/material.dart';
import 'package:flutter_webview_plugin/flutter_webview_plugin.dart';
void main() => runApp(MyApp());
class MyApp extends StatelessWidget {
// This widget is the root of your application.
#override
Widget build(BuildContext context) {
return MaterialApp(
title: 'Flutter Demo',
theme: ThemeData(
primarySwatch: Colors.blue,
),
home: WebInApp(),
);
}
}
class WebInApp extends StatefulWidget {
#override
_WebInAppState createState() => _WebInAppState();
}
class _WebInAppState extends State<WebInApp> {
bool _isVisible = true;
double oldOffset = 0.0;
final flutterWebOlugin = FlutterWebviewPlugin();
void trackOffsetChange(double currentOffset) {
print('current Offset --->> $currentOffset');
print('old Offset --->> $oldOffset');
if (oldOffset < currentOffset) {
print('old Offset In -- IF --->> $oldOffset');
oldOffset = currentOffset;
setState(() {
_isVisible = false;
});
} else {
setState(() {
_isVisible = true;
});
print('old Offset In -- ESLE --->> $oldOffset');
oldOffset = currentOffset;
}
}
#override
void initState() {
super.initState();
flutterWebOlugin.onScrollYChanged.listen((double yOffset) {
trackOffsetChange(yOffset);
});
}
#override
Widget build(BuildContext context) {
return WebviewScaffold(
url: "https://play.google.com/store/apps",
// hidden: true,
appBar: AppBar(
title: Text('WebView'),
),
bottomNavigationBar: AnimatedContainer(
duration: Duration(microseconds: 300),
height: _isVisible ? 60.0 : 0.0,
child: bottomNav(),
),
);
}
}
class bottomNav extends StatelessWidget {
const bottomNav({
Key key,
}) : super(key: key);
#override
Widget build(BuildContext context) {
return BottomNavigationBar(
items: <BottomNavigationBarItem>[
BottomNavigationBarItem(
icon: Icon(Icons.forward),
title: Text('back'),
),
BottomNavigationBarItem(
icon: Icon(Icons.arrow_back),
title: Text('forward'),
),
],
);
}
}