Add support for modal, ephemeral, and contentless routes to Navigator2

Routes can now create a list of widgets, which can be empty (in the case of
contentless routes) or have multiple entries (in the case of modal routes).

Ephemeral routes are handled by keeping a separate list of modal and ephemeral
routes.

packages/flutter/lib/src/material/material_app.dart

@@ -9,6 +9,7 @@ import 'package:flutter/services.dart';
 import 'package:flutter/widgets.dart';
 
 import 'package:flutter/src/widgets/navigator2.dart' as n2;
+import 'package:flutter/src/widgets/page.dart' as n2;
 
 import 'theme.dart';
 import 'title.dart';
@@ -86,12 +87,22 @@ class _MaterialAppState extends State<MaterialApp> {
 
   void _metricHandler(Size size) => setState(() { _size = size; });
 
+  n2.Route _generateRoute(n2.RouteArguments args) {
+    return new n2.PageRoute(
+      builder: (BuildContext context) {
+        RouteArguments routeArgs = new RouteArguments(context: context);
+        return config.routes[args.name](routeArgs);
+      },
+      args: args
+    );
+  }
+
   Widget build(BuildContext context) {
     Widget navigator;
     if (_kUseNavigator2) {
       navigator = new n2.Navigator(
         key: _navigator,
-        routes: config.routes
+        onGenerateRoute: _generateRoute
       );
     } else {
       navigator = new Navigator(

packages/flutter/lib/src/widgets/navigator2.dart

@@ -2,55 +2,54 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-import 'dart:async';
-
-import 'package:flutter/animation.dart';
-
-import 'basic.dart';
 import 'framework.dart';
 import 'overlay.dart';
-import 'transitions.dart';
 
 abstract class Route {
-  /// Override this function to return the widget that this route should display.
-  Widget createWidget();
+  List<Widget> createWidgets() => const <Widget>[];
 
-  Widget _child;
-  OverlayEntry _entry;
+  OverlayEntry get topEntry => _entries.isNotEmpty ? _entries.last : null;
+  OverlayEntry get bottomEntry => _entries.isNotEmpty ? _entries.first : null;
 
-  void willPush() {
-    _child = createWidget();
+  final List<OverlayEntry> _entries = new List<OverlayEntry>();
+
+  void add(OverlayState overlay, OverlayEntry insertionPoint) {
+    List<Widget> widgets = createWidgets();
+    for (Widget widget in widgets) {
+      _entries.add(new OverlayEntry(child: widget));
+      overlay?.insert(_entries.last, above: insertionPoint);
+      insertionPoint = _entries.last;
+    }
   }
 
-  void didPop(dynamic result) {
-    _entry.remove();
+  void remove(dynamic result) {
+    for (OverlayEntry entry in _entries)
+      entry.remove();
   }
 }
 
-typedef Widget RouteBuilder(args);
-typedef RouteBuilder RouteGenerator(String name);
+class RouteArguments {
+  const RouteArguments({ this.name: '<anonymous>', this.mostValuableKeys });
 
-const String _kDefaultPageName = '/';
+  final String name;
+  final Set<Key> mostValuableKeys;
+}
+
+typedef Route RouteFactory(RouteArguments args);
 
 class Navigator extends StatefulComponent {
   Navigator({
     Key key,
-    this.routes,
-    this.onGeneratePage,
-    this.onUnknownPage
+    this.onGenerateRoute,
+    this.onUnknownRoute
   }) : super(key: key) {
-    // To use a navigator, you must at a minimum define the route with the name '/'.
-    assert(routes != null);
-    assert(routes.containsKey(_kDefaultPageName));
+    assert(onGenerateRoute != null);
   }
 
-  final Map<String, RouteBuilder> routes;
-
-  /// you need to implement this if you pushNamed() to names that might not be in routes.
-  final RouteGenerator onGeneratePage;
+  final RouteFactory onGenerateRoute;
+  final RouteFactory onUnknownRoute;
 
-  /// 404 generator. You only need to implement this if you have a way to navigate to arbitrary names.
-  final RouteBuilder onUnknownPage;
+  static const String defaultRouteName = '/';
 
   static NavigatorState of(BuildContext context) {
     NavigatorState result;
@@ -68,139 +67,65 @@ class Navigator extends StatefulComponent {
 }
 
 class NavigatorState extends State<Navigator> {
-  GlobalKey<OverlayState> _overlay = new GlobalKey<OverlayState>();
-  List<Route> _history = new List<Route>();
+  final GlobalKey<OverlayState> _overlay = new GlobalKey<OverlayState>();
+  final List<Route> _ephemeral = new List<Route>();
+  final List<Route> _modal = new List<Route>();
 
   void initState() {
     super.initState();
-    _addRouteToHistory(new PageRoute(
-      builder: config.routes[_kDefaultPageName],
-      name: _kDefaultPageName
-    ));
-  }
-
-  RouteBuilder _generatePage(String name) {
-    assert(config.onGeneratePage != null);
-    return config.onGeneratePage(name);
+    push(config.onGenerateRoute(new RouteArguments(name: Navigator.defaultRouteName)));
   }
 
-  bool get hasPreviousRoute => _history.length > 1;
+  bool get hasPreviousRoute => _modal.length > 1;
 
-  void pushNamed(String name, { Set<Key> mostValuableKeys }) {
-    final RouteBuilder builder = config.routes[name] ?? _generatePage(name) ?? config.onUnknownPage;
-    assert(builder != null); // 404 getting your 404!
-    push(new PageRoute(
-      builder: builder,
-      name: name,
-      mostValuableKeys: mostValuableKeys
-    ));
+  OverlayEntry get _topRouteOverlay {
+    for (Route route in _ephemeral.reversed) {
+      if (route.topEntry != null)
+        return route.topEntry;
     }
-
-  void _addRouteToHistory(Route route) {
-    route.willPush();
-    route._entry = new OverlayEntry(child: route._child);
-    _history.add(route);
+    for (Route route in _modal.reversed) {
+      if (route.topEntry != null)
+        return route.topEntry;
     }
-
-  void push(Route route) {
-    OverlayEntry reference = _history.last._entry;
-    _addRouteToHistory(route);
-    _overlay.currentState.insert(route._entry, above: reference);
+    return null;
   }
 
-  void pop([dynamic result]) {
-    _history.removeLast().didPop(result);
+  void pushNamed(String name, { Set<Key> mostValuableKeys }) {
+    RouteArguments args = new RouteArguments(name: name, mostValuableKeys: mostValuableKeys);
+    push(config.onGenerateRoute(args) ?? config.onUnknownRoute(args));
   }
 
-  Widget build(BuildContext context) {
-    return new Overlay(
-      key: _overlay,
-      initialEntries: <OverlayEntry>[ _history.first._entry ]
-    );
+  void push(Route route) {
+    _popAllEphemeralRoutes();
+    route.add(_overlay.currentState, _topRouteOverlay);
+    _modal.add(route);
   }
-}
-
-abstract class TransitionRoute extends Route {
-  PerformanceView get performance => _performance?.view;
-  Performance _performance;
-
-  Duration get transitionDuration;
 
-  Performance createPerformance() {
-    Duration duration = transitionDuration;
-    assert(duration != null && duration >= Duration.ZERO);
-    return new Performance(duration: duration, debugLabel: debugLabel);
+  void pushEphemeral(Route route) {
+    route.add(_overlay.currentState, _topRouteOverlay);
+    _ephemeral.add(route);
   }
 
-  void willPush() {
-    _performance = createPerformance();
-    _performance.forward();
-    super.willPush();
+  void _popAllEphemeralRoutes() {
+    List<Route> localEphemeral = new List<Route>.from(_ephemeral);
+    _ephemeral.clear();
+    for (Route route in localEphemeral)
+      route.remove(null);
+    assert(_ephemeral.isEmpty);
   }
 
-  Future didPop(dynamic result) async {
-    await _performance.reverse();
-    super.didPop(result);
+  void pop([dynamic result]) {
+    if (_ephemeral.isNotEmpty) {
+      _ephemeral.removeLast().remove(result);
+      return;
+    }
+    _modal.removeLast().remove(result);
   }
-
-  String get debugLabel => '$runtimeType';
-  String toString() => '$runtimeType(performance: $_performance)';
-}
-
-class _Page extends StatefulComponent {
-  _Page({ Key key, this.route }) : super(key: key);
-
-  final PageRoute route;
-
-  _PageState createState() => new _PageState();
-}
-
-class _PageState extends State<_Page> {
-  final AnimatedValue<Point> _position =
-      new AnimatedValue<Point>(const Point(0.0, 75.0), end: Point.origin, curve: Curves.easeOut);
-
-  final AnimatedValue<double> _opacity =
-      new AnimatedValue<double>(0.0, end: 1.0, curve: Curves.easeOut);
 
   Widget build(BuildContext context) {
-    return new SlideTransition(
-      performance: config.route.performance,
-      position: _position,
-      child: new FadeTransition(
-        performance: config.route.performance,
-        opacity: _opacity,
-        child: _invokeBuilder()
-      )
+    return new Overlay(
+      key: _overlay,
+      initialEntries: _modal.first._entries
     );
   }
-
-  Widget _invokeBuilder() {
-    Widget result = config.route.builder(null);
-    assert(() {
-      if (result == null)
-        debugPrint('The builder for route \'${config.route.name}\' returned null. Route builders must never return null.');
-      assert(result != null && 'A route builder returned null. See the previous log message for details.' is String);
-      return true;
-    });
-    return result;
-  }
-}
-
-class PageRoute extends TransitionRoute {
-  PageRoute({
-    this.builder,
-    this.name: '<anonymous>',
-    this.mostValuableKeys
-  }) {
-    assert(builder != null);
-  }
-
-  final RouteBuilder builder;
-  final String name;
-  final Set<Key> mostValuableKeys;
-
-  Duration get transitionDuration => const Duration(milliseconds: 150);
-  Widget createWidget() => new _Page(route: this);
-
-  String get debugLabel => '${super.debugLabel}($name)';
 }

packages/flutter/lib/src/widgets/page.dart

+// Copyright 2015 The Chromium 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/animation.dart';
+
+import 'basic.dart';
+import 'framework.dart';
+import 'navigator2.dart';
+import 'overlay.dart';
+import 'transitions.dart';
+
+abstract class TransitionRoute extends Route {
+  bool get opaque => true;
+
+  PerformanceView get performance => _performance?.view;
+  Performance _performance;
+
+  Duration get transitionDuration;
+
+  Performance createPerformance() {
+    Duration duration = transitionDuration;
+    assert(duration != null && duration >= Duration.ZERO);
+    return new Performance(duration: duration, debugLabel: debugLabel);
+  }
+
+  dynamic _result;
+
+  void _handleStatusChanged(PerformanceStatus status) {
+    if (status == PerformanceStatus.completed && opaque) {
+      bottomEntry.opaque = true;
+    } else if (status == PerformanceStatus.dismissed) {
+      super.remove(_result);
+    }
+  }
+
+  void add(OverlayState overlayer, OverlayEntry insertionPoint) {
+    _performance = createPerformance()
+      ..addStatusListener(_handleStatusChanged)
+      ..forward();
+    super.add(overlayer, insertionPoint);
+  }
+
+  void remove(dynamic result) {
+    _result = result;
+    _performance.reverse();
+  }
+
+  String get debugLabel => '$runtimeType';
+  String toString() => '$runtimeType(performance: $_performance)';
+}
+
+class _Page extends StatefulComponent {
+  _Page({
+    PageRoute route
+  }) : route = route, super(key: new GlobalObjectKey(route));
+
+  final PageRoute route;
+
+  _PageState createState() => new _PageState();
+}
+
+class _PageState extends State<_Page> {
+  final AnimatedValue<Point> _position =
+      new AnimatedValue<Point>(const Point(0.0, 75.0), end: Point.origin, curve: Curves.easeOut);
+
+  final AnimatedValue<double> _opacity =
+      new AnimatedValue<double>(0.0, end: 1.0, curve: Curves.easeOut);
+
+  Widget build(BuildContext context) {
+    return new SlideTransition(
+      performance: config.route.performance,
+      position: _position,
+      child: new FadeTransition(
+        performance: config.route.performance,
+        opacity: _opacity,
+        child: _invokeBuilder()
+      )
+    );
+  }
+
+  Widget _invokeBuilder() {
+    Widget result = config.route.builder(context);
+    assert(() {
+      if (result == null)
+        debugPrint('The builder for route \'${config.route.name}\' returned null. Route builders must never return null.');
+      assert(result != null && 'A route builder returned null. See the previous log message for details.' is String);
+      return true;
+    });
+    return result;
+  }
+}
+
+class PageRoute extends TransitionRoute {
+  PageRoute({
+    this.builder,
+    this.args: const RouteArguments()
+  }) {
+    assert(builder != null);
+    assert(opaque);
+  }
+
+  final WidgetBuilder builder;
+  final RouteArguments args;
+
+  String get name => args.name;
+
+  Duration get transitionDuration => const Duration(milliseconds: 150);
+  List<Widget> createWidgets() => [ new _Page(route: this) ];
+
+  String get debugLabel => '${super.debugLabel}($name)';
+}