PageView seems to ignore PageController's page after state changes #108961
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Labels
found in release: 3.0
Found to occur in 3.0
found in release: 3.1
Found to occur in 3.1
framework
flutter/packages/flutter repository. See also f: labels.
has reproducible steps
The issue has been confirmed reproducible and is ready to work on
P2
Important issues not at the top of the work list
r: fixed
Issue is closed as already fixed in a newer version
Comments
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I figured out my mistake by looking at the Dismissible widget's source code: When DismissDirection is changed tonone, the parent changes because the child is returned directly instead of being wrapped in a GestureDetector. So adding a GlobalKey to the PageView solves the problem. Re-watching this video helped a lot: https://www.youtube.com/watch?v=kn0EOS-ZiIc
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Thanks for reporting this. |
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@xu-baolin I agree, it's definitely unexpected. It could probably be solved by always returning the same hierarchy: The child being wrapped in a |
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Reproducible using the code sample provided above. videoSimulator.Screen.Recording.-.iPhone.13.Pro.-.2022-08-04.at.12.48.21.mp4code sampleimport 'package:flutter/material.dart';
void main() => runApp(const MyApp());
class MyApp extends StatelessWidget {
const MyApp({Key? key}) : super(key: key);
@override
Widget build(BuildContext context) {
return MaterialApp(
title: 'EasyImageViewer Demo',
debugShowCheckedModeBanner: false,
theme: ThemeData(
primarySwatch: Colors.blue,
),
home: const MyPageView(),
);
}
}
class MyPageView extends StatefulWidget {
const MyPageView({Key? key}) : super(key: key);
@override
State<MyPageView> createState() => _MyPageViewState();
}
class _MyPageViewState extends State<MyPageView> {
final PageController _pageController = PageController();
DismissDirection _dismissDirection = DismissDirection.down;
@override
void dispose() {
_pageController.dispose();
super.dispose();
}
@override
Widget build(BuildContext context) {
return MaterialApp(
home: Scaffold(
body: Dismissible(
direction: _dismissDirection,
resizeDuration: null,
onDismissed: (_) {
Navigator.of(context).pop();
},
key: const Key('dismissable_easy_image_viewer_dialog'),
child: PageView(
controller: _pageController,
children: <Widget>[
Container(
color: Colors.red,
child: Center(
child: ElevatedButton(
onPressed: () {
if (_pageController.hasClients) {
_pageController.animateToPage(
1,
duration: const Duration(milliseconds: 400),
curve: Curves.easeInOut,
);
}
},
child: const Text('Next'),
),
),
),
Container(
color: Colors.blue,
child: Center(
child: ElevatedButton(
onPressed: () {
setState(() {
if(_dismissDirection == DismissDirection.none) {
_dismissDirection = DismissDirection.down;
return;
}
_dismissDirection = DismissDirection.none;
});
},
child: const Text('Change Dismiss Direction'),
),
),
),
],
),
),
),
);
}
}
flutter doctor -v |
danagbemava-nc
added
framework
jfahrenkrug
added a commit
to thesmythgroup/easy_image_viewer
that referenced
this issue
Aug 4, 2022
A ticket asked for swipe-to-dismiss (#14) It's easy to implement and now supported with the `swipeDismissible` argument. This allows the user to drag the dialog down to dismiss it. Initially there was a problem when the user zoomed in and tried to pan around on the zoomed-in image: The `Dismissible` widget's GestureDetector would take over and enter the dismissal animation. Watching the image's scale and then changing the Dismissible's `dismissDirection` from `down` to `none` solves the issue. However, additionally a `GlobalObjectKey` was needed for the PageView because Dismissible changes the location of the widget in the widget tree when its `dismissDirection` is changed to `none`. See https://github.com/flutter/flutter/blob/2aa348b9407e96ffe4eca8e8f213c7984afad3f7/packages/flutter/lib/src/widgets/dismissible.dart#L692 See flutter/flutter#108961 See https://www.youtube.com/watch?v=kn0EOS-ZiIc
3 tasks
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@xu-baolin Thanks so much for fixing this! |
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Background
I was trying to add "swipe to dismiss" to my easy_image_viewer project. I wrapped a PageView inside of a
Dismissiblewidget in order to change thedismissDirectionfromdowntononewhen the user has zoomed in to an image (to allow the user to pan around without triggering the dismissal).However, when changing the dismissDirection, the PageView always jumps back to the first page. I had already filed this here #106708, but I was asked by @maheshmnj to provide a minimal example without any dependencies. Here it is :) Could you take another look @maheshmnj? Thanks!
Steps to Reproduce
Expected results: The app stays on the second page
Actual results: The app jumps back to the first page
Code sample
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