Flutter PageView check if page changed using drag gesture or animateToPage() - flutter

Question

In a Scaffold page with something like the following structure
#override
Widget build(BuildContext context){
body: PageView(
controller: _controller;
children: <Widget>[Page1(), Page2(), Page3()];
);
bottomNavigationBar: BottomNavBar(
onItemSelected: (index) => _controller.animateToPage()
)
}
there are two ways to go from Page2() to Page1():
Swipe the screen from left to right
Tap the Page1() icon on the bottomNavigationBar, and thus calling _controller.animateToPage(0)
The problem is, how can I tell if the page is changed through swiping gesture or animateToPage() function?
Thanks.

Answer 1

Maybe you can add a flag to set if animateToPage is ongoing or not.
Sample:
import 'package:flutter/material.dart';
void main() => runApp(Root());
class Root extends StatelessWidget {
#override
Widget build(BuildContext context) {
final PageController controller = PageController();
bool isAnimateToPage = false;
controller.addListener(() {
print('LISTENER isAnimateToPage = $isAnimateToPage');
});
return MaterialApp(
home: Scaffold(
body: Column(
children: <Widget>[
Expanded(
child: PageView(
controller: controller,
onPageChanged: (int page) {
print(
'ONPAGECHANGED isAnimateToPage = $isAnimateToPage ; page = $page');
},
children: <Widget>[
const Center(child: Text('page 1')),
const Center(child: Text('page 2')),
const Center(child: Text('page 3')),
],
),
),
FlatButton(
onPressed: () async {
isAnimateToPage = true;
await controller.animateToPage(
controller.page.toInt() + 1,
duration: const Duration(seconds: 1),
curve: Curves.easeIn,
);
isAnimateToPage = false;
},
child: const Text('Next'),
),
],
),
),
);
}
}