packages/flutter/lib/src/material/page.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:flutter/cupertino.dart';

import 'page_transitions_theme.dart';
import 'theme.dart';

/// A modal route that replaces the entire screen with a platform-adaptive
/// transition.
///
/// {@macro flutter.material.materialRouteTransitionMixin}
///
/// By default, when a modal route is replaced by another, the previous route
/// remains in memory. To free all the resources when this is not necessary, set
/// [maintainState] to false.
///
/// The `fullscreenDialog` property specifies whether the incoming route is a
/// fullscreen modal dialog. On iOS, those routes animate from the bottom to the
/// top rather than horizontally.
///
/// If `barrierDismissible` is true, then pressing the escape key on the keyboard
/// will cause the current route to be popped with null as the value.
///
/// The type `T` specifies the return type of the route which can be supplied as
/// the route is popped from the stack via [Navigator.pop] by providing the
/// optional `result` argument.
///
/// See also:
///
///  * [MaterialRouteTransitionMixin], which provides the material transition
///    for this route.
///  * [MaterialPage], which is a [Page] of this class.
class MaterialPageRoute<T> extends PageRoute<T> with MaterialRouteTransitionMixin<T> {
  /// Construct a MaterialPageRoute whose contents are defined by [builder].
  MaterialPageRoute({
    required this.builder,
    super.settings,
    super.requestFocus,
    this.maintainState = true,
    super.fullscreenDialog,
    super.allowSnapshotting = true,
    super.barrierDismissible = false,
  }) {
    assert(opaque);
  }

  /// Builds the primary contents of the route.
  final WidgetBuilder builder;

  @override
  Widget buildContent(BuildContext context) => builder(context);

  @override
  final bool maintainState;

  @override
  String get debugLabel => '${super.debugLabel}(${settings.name})';
}


/// A mixin that provides platform-adaptive transitions for a [PageRoute].
///
/// {@template flutter.material.materialRouteTransitionMixin}
/// For Android, the entrance transition for the page zooms in and fades in
/// while the exiting page zooms out and fades out. The exit transition is similar,
/// but in reverse.
///
/// For iOS, the page slides in from the right and exits in reverse. The page
/// also shifts to the left in parallax when another page enters to cover it.
/// (These directions are flipped in environments with a right-to-left reading
/// direction.)
/// {@endtemplate}
///
/// See also:
///
///  * [PageTransitionsTheme], which defines the default page transitions used
///    by the [MaterialRouteTransitionMixin.buildTransitions].
///  * [ZoomPageTransitionsBuilder], which is the default page transition used
///    by the [PageTransitionsTheme].
///  * [CupertinoPageTransitionsBuilder], which is the default page transition
///    for iOS and macOS.
mixin MaterialRouteTransitionMixin<T> on PageRoute<T> {
  /// Builds the primary contents of the route.
  @protected
  Widget buildContent(BuildContext context);

  @override
  Duration get transitionDuration => const Duration(milliseconds: 300);

  @override
  Color? get barrierColor => null;

  @override
  String? get barrierLabel => null;

  @override
  DelegatedTransitionBuilder? get delegatedTransition => _delegatedTransition;

  static Widget? _delegatedTransition(BuildContext context, Animation<double> animation, Animation<double> secondaryAnimation, bool allowSnapshotting, Widget? child) {
    final PageTransitionsTheme theme = Theme.of(context).pageTransitionsTheme;
    final TargetPlatform platform = Theme.of(context).platform;
    final DelegatedTransitionBuilder? themeDelegatedTransition = theme.delegatedTransition(platform);
    return themeDelegatedTransition != null ? themeDelegatedTransition(context, animation, secondaryAnimation, allowSnapshotting, child) : null;
  }

  @override
  bool canTransitionTo(TransitionRoute<dynamic> nextRoute) {
    // Don't perform outgoing animation if the next route is a fullscreen dialog,
    // or there is no matching transition to use.
    // Don't perform outgoing animation if the next route is a fullscreen dialog.
    final bool nextRouteIsNotFullscreen = (nextRoute is! PageRoute<T>) || !nextRoute.fullscreenDialog;

    // If the next route has a delegated transition, then this route is able to
    // use that delegated transition to smoothly sync with the next route's
    // transition.
    final bool nextRouteHasDelegatedTransition = nextRoute is ModalRoute<T>
      && nextRoute.delegatedTransition != null;

    // Otherwise if the next route has the same route transition mixin as this
    // one, then this route will already be synced with its transition.
    return nextRouteIsNotFullscreen &&
      ((nextRoute is MaterialRouteTransitionMixin) || nextRouteHasDelegatedTransition);
  }

  @override
  Widget buildPage(
    BuildContext context,
    Animation<double> animation,
    Animation<double> secondaryAnimation,
  ) {
    final Widget result = buildContent(context);
    return Semantics(
      scopesRoute: true,
      explicitChildNodes: true,
      child: result,
    );
  }

  @override
  Widget buildTransitions(BuildContext context, Animation<double> animation, Animation<double> secondaryAnimation, Widget child) {
    final PageTransitionsTheme theme = Theme.of(context).pageTransitionsTheme;
    return theme.buildTransitions<T>(this, context, animation, secondaryAnimation, child);
  }
}

/// A page that creates a material style [PageRoute].
///
/// {@macro flutter.material.materialRouteTransitionMixin}
///
/// By default, when the created route is replaced by another, the previous
/// route remains in memory. To free all the resources when this is not
/// necessary, set [maintainState] to false.
///
/// The `fullscreenDialog` property specifies whether the created route is a
/// fullscreen modal dialog. On iOS, those routes animate from the bottom to the
/// top rather than horizontally.
///
/// The type `T` specifies the return type of the route which can be supplied as
/// the route is popped from the stack via [Navigator.transitionDelegate] by
/// providing the optional `result` argument to the
/// [RouteTransitionRecord.markForPop] in the [TransitionDelegate.resolve].
///
/// See also:
///
///  * [MaterialPageRoute], which is the [PageRoute] version of this class
class MaterialPage<T> extends Page<T> {
  /// Creates a material page.
  const MaterialPage({
    required this.child,
    this.maintainState = true,
    this.fullscreenDialog = false,
    this.allowSnapshotting = true,
    super.key,
    super.canPop,
    super.onPopInvoked,
    super.name,
    super.arguments,
    super.restorationId,
  });

  /// The content to be shown in the [Route] created by this page.
  final Widget child;

  /// {@macro flutter.widgets.ModalRoute.maintainState}
  final bool maintainState;

  /// {@macro flutter.widgets.PageRoute.fullscreenDialog}
  final bool fullscreenDialog;

  /// {@macro flutter.widgets.TransitionRoute.allowSnapshotting}
  final bool allowSnapshotting;

  @override
  Route<T> createRoute(BuildContext context) {
    return _PageBasedMaterialPageRoute<T>(page: this, allowSnapshotting: allowSnapshotting);
  }
}

// A page-based version of MaterialPageRoute.
//
// This route uses the builder from the page to build its content. This ensures
// the content is up to date after page updates.
class _PageBasedMaterialPageRoute<T> extends PageRoute<T> with MaterialRouteTransitionMixin<T> {
  _PageBasedMaterialPageRoute({
    required MaterialPage<T> page,
    super.allowSnapshotting,
  }) : super(settings: page) {
    assert(opaque);
  }

  MaterialPage<T> get _page => settings as MaterialPage<T>;

  @override
  Widget buildContent(BuildContext context) {
    return _page.child;
  }

  @override
  bool get maintainState => _page.maintainState;

  @override
  bool get fullscreenDialog => _page.fullscreenDialog;

  @override
  String get debugLabel => '${super.debugLabel}(${_page.name})';
}