Reverts: flutter/flutter#139164
Initiated by: chunhtai
Reason for reverting: hard breaking change
Original PR Author: chunhtai
Reviewed By: {justinmc}
This change reverts the following previous change:
Adds a generic type and pop result to popscope and its friend.
The use cases are to be able to capture the result when the pop is called.
migration guide: https://github.com/flutter/website/pull/9872
Adds a generic type and pop result to popscope and its friend.
The use cases are to be able to capture the result when the pop is called.
migration guide: https://github.com/flutter/website/pull/9872
Addresses #63507, and is a follow up to the engine PR https://github.com/flutter/engine/pull/46857
Changes the font family string when attempting to use Apple system fonts to the new proxies added by the engine. For the "Text" font this will be more secure in the future against possible changes to Apple's API. For the "Display" font, this will now work correctly when it didn't before.
I checked the letter spacing values against a native app for all font sizes between 17-28. I made a few adjustments to better match native, but especially for the "Text" font we were either really close, or close enough to not make a large breaking change to default fonts worth it.
| Before | After |
| ------------- | ------------- |
| <img width="466" alt="Screenshot 2023-11-02 at 11 45 12â¯AM" src="https://github.com/flutter/flutter/assets/58190796/627ed8ac-d848-4f71-aa62-a467b8aac62d"> | <img width="383" alt="Screenshot 2023-11-02 at 11 46 25â¯AM" src="https://github.com/flutter/flutter/assets/58190796/9a502021-7d2b-4e14-98f1-86971b3830a5"> |
The smaller text in both the before and after should be the same. The large system font that Flutter used before was incorrect, which caused it to look more spread out. Now we use the correct font.
This PR aims to support Android's predictive back gesture when popping the entire Flutter app. Predictive route transitions between routes inside of a Flutter app will come later.
<img width="200" src="https://user-images.githubusercontent.com/389558/217918109-945febaa-9086-41cc-a476-1a189c7831d8.gif" />
### Trying it out
If you want to try this feature yourself, here are the necessary steps:
1. Run Android 33 or above.
1. Enable the feature flag for predictive back on the device under "Developer
options".
1. Create a Flutter project, or clone [my example project](https://github.com/justinmc/flutter_predictive_back_examples).
1. Set `android:enableOnBackInvokedCallback="true"` in
android/app/src/main/AndroidManifest.xml (already done in the example project).
1. Check out this branch.
1. Run the app. Perform a back gesture (swipe from the left side of the
screen).
You should see the predictive back animation like in the animation above and be able to commit or cancel it.
### go_router support
go_router works with predictive back out of the box because it uses a Navigator internally that dispatches NavigationNotifications!
~~go_router can be supported by adding a listener to the router and updating SystemNavigator.setFrameworkHandlesBack.~~
Similar to with nested Navigators, nested go_routers is supported by using a PopScope widget.
<details>
<summary>Full example of nested go_routers</summary>
```dart
// 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:go_router/go_router.dart';
import 'package:flutter/material.dart';
import 'package:flutter/scheduler.dart';
void main() => runApp(_MyApp());
class _MyApp extends StatelessWidget {
final GoRouter router = GoRouter(
routes: <RouteBase>[
GoRoute(
path: '/',
builder: (BuildContext context, GoRouterState state) => _HomePage(),
),
GoRoute(
path: '/nested_navigators',
builder: (BuildContext context, GoRouterState state) => _NestedGoRoutersPage(),
),
],
);
@override
Widget build(BuildContext context) {
return MaterialApp.router(
routerConfig: router,
);
}
}
class _HomePage extends StatelessWidget {
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: const Text('Nested Navigators Example'),
),
body: Center(
child: Column(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
const Text('Home Page'),
const Text('A system back gesture here will exit the app.'),
const SizedBox(height: 20.0),
ListTile(
title: const Text('Nested go_router route'),
subtitle: const Text('This route has another go_router in addition to the one used with MaterialApp above.'),
onTap: () {
context.push('/nested_navigators');
},
),
],
),
),
);
}
}
class _NestedGoRoutersPage extends StatefulWidget {
@override
State<_NestedGoRoutersPage> createState() => _NestedGoRoutersPageState();
}
class _NestedGoRoutersPageState extends State<_NestedGoRoutersPage> {
late final GoRouter _router;
final GlobalKey<NavigatorState> _nestedNavigatorKey = GlobalKey<NavigatorState>();
// If the nested navigator has routes that can be popped, then we want to
// block the root navigator from handling the pop so that the nested navigator
// can handle it instead.
bool get _popEnabled {
// canPop will throw an error if called before build. Is this the best way
// to avoid that?
return _nestedNavigatorKey.currentState == null ? true : !_router.canPop();
}
void _onRouterChanged() {
// Here the _router reports the location correctly, but canPop is still out
// of date. Hence the post frame callback.
SchedulerBinding.instance.addPostFrameCallback((Duration duration) {
setState(() {});
});
}
@override
void initState() {
super.initState();
final BuildContext rootContext = context;
_router = GoRouter(
navigatorKey: _nestedNavigatorKey,
routes: [
GoRoute(
path: '/',
builder: (BuildContext context, GoRouterState state) => _LinksPage(
title: 'Nested once - home route',
backgroundColor: Colors.indigo,
onBack: () {
rootContext.pop();
},
buttons: <Widget>[
TextButton(
onPressed: () {
context.push('/two');
},
child: const Text('Go to another route in this nested Navigator'),
),
],
),
),
GoRoute(
path: '/two',
builder: (BuildContext context, GoRouterState state) => _LinksPage(
backgroundColor: Colors.indigo.withBlue(255),
title: 'Nested once - page two',
),
),
],
);
_router.addListener(_onRouterChanged);
}
@override
void dispose() {
_router.removeListener(_onRouterChanged);
super.dispose();
}
@override
Widget build(BuildContext context) {
return PopScope(
popEnabled: _popEnabled,
onPopped: (bool success) {
if (success) {
return;
}
_router.pop();
},
child: Router<Object>.withConfig(
restorationScopeId: 'router-2',
config: _router,
),
);
}
}
class _LinksPage extends StatelessWidget {
const _LinksPage ({
required this.backgroundColor,
this.buttons = const <Widget>[],
this.onBack,
required this.title,
});
final Color backgroundColor;
final List<Widget> buttons;
final VoidCallback? onBack;
final String title;
@override
Widget build(BuildContext context) {
return Scaffold(
backgroundColor: backgroundColor,
body: Center(
child: Column(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
Text(title),
//const Text('A system back here will go back to Nested Navigators Page One'),
...buttons,
TextButton(
onPressed: onBack ?? () {
context.pop();
},
child: const Text('Go back'),
),
],
),
),
);
}
}
```
</details>
### Resources
Fixes https://github.com/flutter/flutter/issues/109513
Depends on engine PR https://github.com/flutter/engine/pull/39208✔️
Design doc: https://docs.google.com/document/d/1BGCWy1_LRrXEB6qeqTAKlk-U2CZlKJ5xI97g45U7azk/edit#
Migration guide: https://github.com/flutter/website/pull/8952
Adds Navigator.maybeOf to replace calling Navigator.of(context, nullOk: true), and removes the nullOk parameter. Also changes Navigator.of to return a non-nullable value, and removes many (120!) instances of the ! operator, reducing the possible places where a null dereference could occur.
Move Flutter Gallery to dev/integration_tests/ as it is an older copy used only for testing. The current version of the Flutter Gallery now lives in https://github.com/flutter/gallery.
