implement tab view

Author: zhuxingwei

Runtime/cupertino/tab_view.cs

@@ -0,0 +1,141 @@
+using System.Collections.Generic;
+using Unity.UIWidgets.foundation;
+using Unity.UIWidgets.widgets;
+
+namespace Unity.UIWidgets.cupertino {
+    public class CupertinoTabView : StatefulWidget {
+        public CupertinoTabView(
+            Key key = null,
+            WidgetBuilder builder = null,
+            GlobalKey<NavigatorState> navigatorKey = null,
+            string defaultTitle = null,
+            Dictionary<string, WidgetBuilder> routes = null,
+            RouteFactory onGenerateRoute = null,
+            RouteFactory onUnknownRoute = null,
+            List<NavigatorObserver> navigatorObservers = null
+        ) : base(key: key) {
+            this.builder = builder;
+            this.navigatorKey = navigatorKey;
+            this.defaultTitle = defaultTitle;
+            this.routes = routes;
+            this.onGenerateRoute = onGenerateRoute;
+            this.onUnknownRoute = onUnknownRoute;
+            this.navigatorObservers = navigatorObservers ?? new List<NavigatorObserver>();
+        }
+
+        public readonly WidgetBuilder builder;
+
+        public readonly GlobalKey<NavigatorState> navigatorKey;
+
+        public readonly string defaultTitle;
+
+        public readonly Dictionary<string, WidgetBuilder> routes;
+
+        public readonly RouteFactory onGenerateRoute;
+
+        public readonly RouteFactory onUnknownRoute;
+
+        public readonly List<NavigatorObserver> navigatorObservers;
+
+        public override State createState() {
+            return new _CupertinoTabViewState();
+        }
+    }
+
+    class _CupertinoTabViewState : State<CupertinoTabView> {
+        HeroController _heroController;
+        List<NavigatorObserver> _navigatorObservers;
+
+        public override void initState() {
+            base.initState();
+            this._heroController = CupertinoApp.createCupertinoHeroController();
+            this._updateObservers();
+        }
+
+        public override void didUpdateWidget(StatefulWidget oldWidget) {
+            base.didUpdateWidget(oldWidget);
+            CupertinoTabView _oldWidget = (CupertinoTabView) oldWidget;
+            if (this.widget.navigatorKey != _oldWidget.navigatorKey
+                || this.widget.navigatorObservers != _oldWidget.navigatorObservers) {
+                this._updateObservers();
+            }
+        }
+
+        void _updateObservers() {
+            this._navigatorObservers =
+                new List<NavigatorObserver>(this.widget.navigatorObservers);
+            this._navigatorObservers.Add(this._heroController);
+        }
+
+        public override Widget build(BuildContext context) {
+            return new Navigator(
+                key: this.widget.navigatorKey,
+                onGenerateRoute: this._onGenerateRoute,
+                onUnknownRoute: this._onUnknownRoute,
+                observers: this._navigatorObservers
+            );
+        }
+
+        Route _onGenerateRoute(RouteSettings settings) {
+            string name = settings.name;
+            WidgetBuilder routeBuilder = null;
+            string title = null;
+            if (name == Navigator.defaultRouteName && this.widget.builder != null) {
+                routeBuilder = this.widget.builder;
+                title = this.widget.defaultTitle;
+            }
+            else if (this.widget.routes != null) {
+                routeBuilder = this.widget.routes[name];
+            }
+
+            if (routeBuilder != null) {
+                return new CupertinoPageRoute(
+                    builder: routeBuilder,
+                    title: title,
+                    settings: settings
+                );
+            }
+
+            if (this.widget.onGenerateRoute != null) {
+                return this.widget.onGenerateRoute(settings);
+            }
+
+            return null;
+        }
+
+        Route _onUnknownRoute(RouteSettings settings) {
+            D.assert(() => {
+                if (this.widget.onUnknownRoute == null) {
+                    throw new UIWidgetsError(
+                        $"Could not find a generator for route {settings} in the {this.GetType()}.\n" +
+                        "Generators for routes are searched for in the following order:\n" +
+                        " 1. For the \"/\" route, the \"builder\" property, if non-null, is used.\n" +
+                        " 2. Otherwise, the \"routes\" table is used, if it has an entry for " +
+                        "the route.\n" +
+                        " 3. Otherwise, onGenerateRoute is called. It should return a " +
+                        "non-null value for any valid route not handled by \"builder\" and \"routes\".\n" +
+                        " 4. Finally if all else fails onUnknownRoute is called.\n" +
+                        "Unfortunately, onUnknownRoute was not set."
+                    );
+                }
+
+                return true;
+            });
+
+            Route result = this.widget.onUnknownRoute(settings);
+            D.assert(() => {
+                if (result == null) {
+                    throw new UIWidgetsError(
+                        "The onUnknownRoute callback returned null.\n" +
+                        $"When the {this.GetType()} requested the route {settings} from its " +
+                        "onUnknownRoute callback, the callback returned null. Such callbacks " +
+                        "must never return null."
+                    );
+                }
+
+                return true;
+            });
+            return result;
+        }
+    }
+}