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Reland root predictive back (#132249)
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Root predictive back (flutter/flutter#120385) was reverted in flutter/flutter#132167.  This PR is an attempt to reland it.

The reversion happened due to failed Google tests (b/295073110).
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justinmc authored Aug 17, 2023
1 parent ced3e76 commit f68d03f
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Showing 36 changed files with 3,224 additions and 297 deletions.
Original file line number Diff line number Diff line change
Expand Up @@ -48,9 +48,9 @@ class CupertinoNavigationDemo extends StatelessWidget {

@override
Widget build(BuildContext context) {
return WillPopScope(
return PopScope(
// Prevent swipe popping of this page. Use explicit exit buttons only.
onWillPop: () => Future<bool>.value(true),
canPop: false,
child: DefaultTextStyle(
style: CupertinoTheme.of(context).textTheme.textStyle,
child: CupertinoTabScaffold(
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Original file line number Diff line number Diff line change
Expand Up @@ -3,6 +3,7 @@
// found in the LICENSE file.

import 'package:flutter/material.dart';
import 'package:flutter/services.dart';
import 'package:intl/intl.dart';

// This demo is based on
Expand Down Expand Up @@ -109,16 +110,15 @@ class FullScreenDialogDemoState extends State<FullScreenDialogDemo> {
bool _hasName = false;
late String _eventName;

Future<bool> _onWillPop() async {
_saveNeeded = _hasLocation || _hasName || _saveNeeded;
if (!_saveNeeded) {
return true;
Future<void> _handlePopInvoked(bool didPop) async {
if (didPop) {
return;
}

final ThemeData theme = Theme.of(context);
final TextStyle dialogTextStyle = theme.textTheme.titleMedium!.copyWith(color: theme.textTheme.bodySmall!.color);

return showDialog<bool>(
final bool? shouldDiscard = await showDialog<bool>(
context: context,
builder: (BuildContext context) {
return AlertDialog(
Expand All @@ -130,19 +130,31 @@ class FullScreenDialogDemoState extends State<FullScreenDialogDemo> {
TextButton(
child: const Text('CANCEL'),
onPressed: () {
Navigator.of(context).pop(false); // Pops the confirmation dialog but not the page.
// Pop the confirmation dialog and indicate that the page should
// not be popped.
Navigator.of(context).pop(false);
},
),
TextButton(
child: const Text('DISCARD'),
onPressed: () {
Navigator.of(context).pop(true); // Returning true to _onWillPop will pop again.
// Pop the confirmation dialog and indicate that the page should
// be popped, too.
Navigator.of(context).pop(true);
},
),
],
);
},
) as Future<bool>;
);

if (shouldDiscard ?? false) {
// Since this is the root route, quit the app where possible by invoking
// the SystemNavigator. If this wasn't the root route, then
// Navigator.maybePop could be used instead.
// See https://github.com/flutter/flutter/issues/11490
SystemNavigator.pop();
}
}

@override
Expand All @@ -162,7 +174,8 @@ class FullScreenDialogDemoState extends State<FullScreenDialogDemo> {
],
),
body: Form(
onWillPop: _onWillPop,
canPop: !_saveNeeded && !_hasLocation && !_hasName,
onPopInvoked: _handlePopInvoked,
child: Scrollbar(
child: ListView(
primary: true,
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Original file line number Diff line number Diff line change
Expand Up @@ -143,10 +143,9 @@ class TextFormFieldDemoState extends State<TextFormFieldDemo> {
return null;
}

Future<bool> _warnUserAboutInvalidData() async {
final FormState? form = _formKey.currentState;
if (form == null || !_formWasEdited || form.validate()) {
return true;
Future<void> _handlePopInvoked(bool didPop) async {
if (didPop) {
return;
}

final bool? result = await showDialog<bool>(
Expand All @@ -168,7 +167,14 @@ class TextFormFieldDemoState extends State<TextFormFieldDemo> {
);
},
);
return result!;

if (result ?? false) {
// Since this is the root route, quit the app where possible by invoking
// the SystemNavigator. If this wasn't the root route, then
// Navigator.maybePop could be used instead.
// See https://github.com/flutter/flutter/issues/11490
SystemNavigator.pop();
}
}

@override
Expand All @@ -185,7 +191,8 @@ class TextFormFieldDemoState extends State<TextFormFieldDemo> {
child: Form(
key: _formKey,
autovalidateMode: _autovalidateMode,
onWillPop: _warnUserAboutInvalidData,
canPop: _formKey.currentState == null || !_formWasEdited || _formKey.currentState!.validate(),
onPopInvoked: _handlePopInvoked,
child: Scrollbar(
child: SingleChildScrollView(
primary: true,
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Original file line number Diff line number Diff line change
Expand Up @@ -3,7 +3,6 @@
// found in the LICENSE file.

import 'package:flutter/material.dart';
import 'package:flutter/services.dart';
import 'package:scoped_model/scoped_model.dart';

import 'colors.dart';
Expand Down Expand Up @@ -361,14 +360,12 @@ class ExpandingBottomSheetState extends State<ExpandingBottomSheet> with TickerP

// Closes the cart if the cart is open, otherwise exits the app (this should
// only be relevant for Android).
Future<bool> _onWillPop() async {
if (!_isOpen) {
await SystemNavigator.pop();
return true;
void _handlePopInvoked(bool didPop) {
if (didPop) {
return;
}

close();
return true;
}

@override
Expand All @@ -378,8 +375,9 @@ class ExpandingBottomSheetState extends State<ExpandingBottomSheet> with TickerP
duration: const Duration(milliseconds: 225),
curve: Curves.easeInOut,
alignment: FractionalOffset.topLeft,
child: WillPopScope(
onWillPop: _onWillPop,
child: PopScope(
canPop: !_isOpen,
onPopInvoked: _handlePopInvoked,
child: AnimatedBuilder(
animation: widget.hideController,
builder: _buildSlideAnimation,
Expand Down
14 changes: 7 additions & 7 deletions dev/integration_tests/flutter_gallery/lib/gallery/home.dart
Original file line number Diff line number Diff line change
Expand Up @@ -325,14 +325,14 @@ class _GalleryHomeState extends State<GalleryHome> with SingleTickerProviderStat
backgroundColor: isDark ? _kFlutterBlue : theme.primaryColor,
body: SafeArea(
bottom: false,
child: WillPopScope(
onWillPop: () {
// Pop the category page if Android back button is pressed.
if (_category != null) {
setState(() => _category = null);
return Future<bool>.value(false);
child: PopScope(
canPop: _category == null,
onPopInvoked: (bool didPop) {
if (didPop) {
return;
}
return Future<bool>.value(true);
// Pop the category page if Android back button is pressed.
setState(() => _category = null);
},
child: Backdrop(
backTitle: const Text('Options'),
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Original file line number Diff line number Diff line change
Expand Up @@ -71,14 +71,10 @@ class _HomeState extends State<Home> with TickerProviderStateMixin<Home> {

@override
Widget build(BuildContext context) {
return WillPopScope(
onWillPop: () async {
return NavigatorPopHandler(
onPop: () {
final NavigatorState navigator = navigatorKeys[selectedIndex].currentState!;
if (!navigator.canPop()) {
return true;
}
navigator.pop();
return false;
},
child: Scaffold(
body: SafeArea(
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166 changes: 166 additions & 0 deletions examples/api/lib/widgets/form/form.1.dart
Original file line number Diff line number Diff line change
@@ -0,0 +1,166 @@
// Copyright 2014 The Flutter Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

import 'package:flutter/material.dart';
import 'package:flutter/services.dart';

/// This sample demonstrates showing a confirmation dialog when the user
/// attempts to navigate away from a page with unsaved [Form] data.
void main() => runApp(const FormApp());

class FormApp extends StatelessWidget {
const FormApp({
super.key,
});

@override
Widget build(BuildContext context) {
return MaterialApp(
home: Scaffold(
appBar: AppBar(
title: const Text('Confirmation Dialog Example'),
),
body: Center(
child: _SaveableForm(),
),
),
);
}
}

class _SaveableForm extends StatefulWidget {
@override
State<_SaveableForm> createState() => _SaveableFormState();
}

class _SaveableFormState extends State<_SaveableForm> {
final TextEditingController _controller = TextEditingController();
String _savedValue = '';
bool _isDirty = false;

@override
void initState() {
super.initState();
_controller.addListener(_onChanged);
}

@override
void dispose() {
_controller.removeListener(_onChanged);
super.dispose();
}

void _onChanged() {
final bool nextIsDirty = _savedValue != _controller.text;
if (nextIsDirty == _isDirty) {
return;
}
setState(() {
_isDirty = nextIsDirty;
});
}

Future<void> _showDialog() async {
final bool? shouldDiscard = await showDialog<bool>(
context: context,
builder: (BuildContext context) {
return AlertDialog(
title: const Text('Are you sure?'),
content: const Text('Any unsaved changes will be lost!'),
actions: <Widget>[
TextButton(
child: const Text('Yes, discard my changes'),
onPressed: () {
Navigator.pop(context, true);
},
),
TextButton(
child: const Text('No, continue editing'),
onPressed: () {
Navigator.pop(context, false);
},
),
],
);
},
);

if (shouldDiscard ?? false) {
// Since this is the root route, quit the app where possible by invoking
// the SystemNavigator. If this wasn't the root route, then
// Navigator.maybePop could be used instead.
// See https://github.com/flutter/flutter/issues/11490
SystemNavigator.pop();
}
}

void _save(String? value) {
setState(() {
_savedValue = value ?? '';
});
}

@override
Widget build(BuildContext context) {
return Center(
child: Column(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
const Text('If the field below is unsaved, a confirmation dialog will be shown on back.'),
const SizedBox(height: 20.0),
Form(
canPop: !_isDirty,
onPopInvoked: (bool didPop) {
if (didPop) {
return;
}
_showDialog();
},
autovalidateMode: AutovalidateMode.always,
child: Column(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
TextFormField(
controller: _controller,
onFieldSubmitted: (String? value) {
_save(value);
},
),
TextButton(
onPressed: () {
_save(_controller.text);
},
child: Row(
children: <Widget>[
const Text('Save'),
if (_controller.text.isNotEmpty)
Icon(
_isDirty ? Icons.warning : Icons.check,
),
],
),
),
],
),
),
TextButton(
onPressed: () {
if (_isDirty) {
_showDialog();
return;
}
// Since this is the root route, quit the app where possible by
// invoking the SystemNavigator. If this wasn't the root route,
// then Navigator.maybePop could be used instead.
// See https://github.com/flutter/flutter/issues/11490
SystemNavigator.pop();
},
child: const Text('Go back'),
),
],
),
);
}
}
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