| // 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 'framework.dart'; |
| import 'navigator.dart'; |
| import 'routes.dart'; |
| |
| /// Registers a callback to veto attempts by the user to dismiss the enclosing |
| /// [ModalRoute]. |
| /// |
| /// {@tool dartpad} |
| /// Whenever the back button is pressed, you will get a callback at [onWillPop], |
| /// which returns a [Future]. If the [Future] returns true, the screen is |
| /// popped. |
| /// |
| /// ** See code in examples/api/lib/widgets/will_pop_scope/will_pop_scope.0.dart ** |
| /// {@end-tool} |
| /// |
| /// See also: |
| /// |
| /// * [ModalRoute.addScopedWillPopCallback] and [ModalRoute.removeScopedWillPopCallback], |
| /// which this widget uses to register and unregister [onWillPop]. |
| /// * [Form], which provides an `onWillPop` callback that enables the form |
| /// to veto a `pop` initiated by the app's back button. |
| /// |
| class WillPopScope extends StatefulWidget { |
| /// Creates a widget that registers a callback to veto attempts by the user to |
| /// dismiss the enclosing [ModalRoute]. |
| /// |
| /// The [child] argument must not be null. |
| const WillPopScope({ |
| super.key, |
| required this.child, |
| required this.onWillPop, |
| }) : assert(child != null); |
| |
| /// The widget below this widget in the tree. |
| /// |
| /// {@macro flutter.widgets.ProxyWidget.child} |
| final Widget child; |
| |
| /// Called to veto attempts by the user to dismiss the enclosing [ModalRoute]. |
| /// |
| /// If the callback returns a Future that resolves to false, the enclosing |
| /// route will not be popped. |
| final WillPopCallback? onWillPop; |
| |
| @override |
| State<WillPopScope> createState() => _WillPopScopeState(); |
| } |
| |
| class _WillPopScopeState extends State<WillPopScope> { |
| ModalRoute<dynamic>? _route; |
| |
| @override |
| void didChangeDependencies() { |
| super.didChangeDependencies(); |
| if (widget.onWillPop != null) { |
| _route?.removeScopedWillPopCallback(widget.onWillPop!); |
| } |
| _route = ModalRoute.of(context); |
| if (widget.onWillPop != null) { |
| _route?.addScopedWillPopCallback(widget.onWillPop!); |
| } |
| } |
| |
| @override |
| void didUpdateWidget(WillPopScope oldWidget) { |
| super.didUpdateWidget(oldWidget); |
| if (widget.onWillPop != oldWidget.onWillPop && _route != null) { |
| if (oldWidget.onWillPop != null) { |
| _route!.removeScopedWillPopCallback(oldWidget.onWillPop!); |
| } |
| if (widget.onWillPop != null) { |
| _route!.addScopedWillPopCallback(widget.onWillPop!); |
| } |
| } |
| } |
| |
| @override |
| void dispose() { |
| if (widget.onWillPop != null) { |
| _route?.removeScopedWillPopCallback(widget.onWillPop!); |
| } |
| super.dispose(); |
| } |
| |
| @override |
| Widget build(BuildContext context) => widget.child; |
| } |