Support for settings fly-in animation

packages/flutter/example/widgets/navigation.dart

@@ -10,9 +10,9 @@ List<Route> routes = [
   new Route(
     name: 'home',
     builder: (navigator, route) => new Container(
-      padding: const EdgeDims.all(20.0),
+      padding: const EdgeDims.all(30.0),
       decoration: new BoxDecoration(backgroundColor: const Color(0xFFCCCCCC)),
-      child: new Block([
+      child: new Flex([
         new Text("You are at home"),
         new RaisedButton(
           child: new Text('GO SHOPPING'),
@@ -22,7 +22,7 @@ List<Route> routes = [
           child: new Text('START ADVENTURE'),
           onPressed: () => navigator.pushNamed('adventure')
         )
-      ])
+      ], direction: FlexDirection.vertical, alignItems: FlexAlignItems.center)
     )
   ),
   new Route(
@@ -30,7 +30,7 @@ List<Route> routes = [
     builder: (navigator, route) => new Container(
       padding: const EdgeDims.all(20.0),
       decoration: new BoxDecoration(backgroundColor: const Color(0xFFBF5FFF)),
-      child: new Block([
+      child: new Flex([
         new Text("Village Shop"),
         new RaisedButton(
           child: new Text('RETURN HOME'),
@@ -40,7 +40,7 @@ List<Route> routes = [
           child: new Text('GO TO DUNGEON'),
           onPressed: () => navigator.push(routes[2])
         )
-      ])
+      ], direction: FlexDirection.vertical)
     )
   ),
   new Route(
@@ -48,13 +48,13 @@ List<Route> routes = [
     builder: (navigator, route) => new Container(
       padding: const EdgeDims.all(20.0),
       decoration: new BoxDecoration(backgroundColor: const Color(0xFFDC143C)),
-      child: new Block([
+      child: new Flex([
         new Text("Monster's Lair"),
         new RaisedButton(
           child: new Text('NO WAIT! GO BACK!'),
           onPressed: () => navigator.pop()
         )
-      ])
+      ], direction: FlexDirection.vertical)
     )
   )
 ];

packages/flutter/lib/widgets/navigator.dart

@@ -2,7 +2,12 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+import 'package:sky/animation/animation_performance.dart';
+import 'package:sky/animation/curves.dart';
+import 'package:sky/widgets/animated_component.dart';
+import 'package:sky/widgets/animation_builder.dart';
 import 'package:sky/widgets/basic.dart';
+import 'package:vector_math/vector_math.dart';
 
 typedef Widget Builder(Navigator navigator, RouteBase route);
 
@@ -27,7 +32,7 @@ class RouteState extends RouteBase {
   RouteBase route;
   Function callback;
 
-  Widget build(Navigator navigator, _) => route.build(navigator, this);
+  Widget build(Navigator navigator, RouteBase route) => null;
 
   void popState() {
     if (callback != null)
@@ -35,6 +40,92 @@ class RouteState extends RouteBase {
   }
 }
 
+// TODO(jackson): Refactor this into its own file
+// and support multiple transition types
+const Duration _kTransitionDuration = const Duration(milliseconds: 200);
+const Point _kTransitionStartPoint = const Point(0.0, 100.0);
+enum TransitionDirection { forward, reverse }
+class Transition extends AnimatedComponent {
+  Transition({ this.content, this.direction, this.onDismissed, this.interactive });
+  Widget content;
+  TransitionDirection direction;
+  bool interactive;
+  Function onDismissed;
+
+  AnimatedType<Point> _position;
+  AnimatedType<double> _opacity;
+  AnimationPerformance _performance;
+
+  void initState() {
+    _position = new AnimatedType<Point>(_kTransitionStartPoint)
+      ..end = Point.origin
+      ..curve = easeOut;
+    _opacity = new AnimatedType<double>(0.0, end: 1.0)
+      ..curve = easeOut;
+    _performance = new AnimationPerformance()
+      ..duration = _kTransitionDuration
+      ..variable = new AnimatedList([_position, _opacity])
+      ..addListener(_checkDismissed);
+    if (direction == TransitionDirection.reverse)
+      _performance.progress = 1.0;
+    watch(_performance);
+    _start();
+  }
+
+  void _start() {
+    _dismissed = false;
+    switch (direction) {
+      case TransitionDirection.forward:
+      _performance.play();
+      break;
+      case TransitionDirection.reverse:
+      _performance.reverse();
+      break;
+    }
+  }
+
+  void syncFields(Transition source) {
+    content = source.content;
+    if (direction != source.direction) {
+      direction = source.direction;
+      _start();
+    }
+    onDismissed = source.onDismissed;
+    super.syncFields(source);
+  }
+
+  bool _dismissed = false;
+  void _checkDismissed() {
+    if (!_dismissed &&
+        direction == TransitionDirection.reverse &&
+        _performance.isDismissed) {
+      if (onDismissed != null)
+        onDismissed();
+      _dismissed = true;
+    }
+  }
+
+  Widget build() {
+    Matrix4 transform = new Matrix4.identity()
+      ..translate(_position.value.x, _position.value.y);
+    // TODO(jackson): Hit testing should ignore transform
+    // TODO(jackson): Block input unless content is interactive
+    return new Transform(
+      transform: transform,
+      child: new Opacity(
+        opacity: _opacity.value,
+        child: content
+      )
+    );
+  }
+}
+
+class HistoryEntry {
+  HistoryEntry(this.route);
+  final RouteBase route;
+  // TODO(jackson): Keep track of the requested transition
+}
+
 class NavigationState {
 
   NavigationState(List<Route> routes) {
@@ -42,16 +133,15 @@ class NavigationState {
       if (route.name != null)
         namedRoutes[route.name] = route;
     }
-    history.add(routes[0]);
+    history.add(new HistoryEntry(routes[0]));
   }
 
-  List<RouteBase> history = new List<RouteBase>();
+  List<HistoryEntry> history = new List<HistoryEntry>();
   int historyIndex = 0;
   Map<String, RouteBase> namedRoutes = new Map<String, RouteBase>();
 
-  RouteBase get currentRoute => history[historyIndex];
+  RouteBase get currentRoute => history[historyIndex].route;
   bool hasPrevious() => historyIndex > 0;
-  bool hasNext() => history.length > historyIndex + 1;
 
   void pushNamed(String name) {
     Route route = namedRoutes[name];
@@ -60,16 +150,15 @@ class NavigationState {
   }
 
   void push(RouteBase route) {
-    // Discard future history
-    history.removeRange(historyIndex + 1, history.length);
-    historyIndex = history.length;
-    history.add(route);
+    HistoryEntry historyEntry = new HistoryEntry(route);
+    history.insert(historyIndex + 1, historyEntry);
+    historyIndex++;
   }
 
   void pop() {
     if (historyIndex > 0) {
-      history[historyIndex].popState();
-      history.removeLast();
+      HistoryEntry entry = history[historyIndex];
+      entry.route.popState();
       historyIndex--;
     }
   }
@@ -115,6 +204,26 @@ class Navigator extends StatefulComponent {
   }
 
   Widget build() {
-    return state.currentRoute.build(this, state.currentRoute);
+    List<Widget> visibleRoutes = new List<Widget>();
+    for (int i = 0; i < state.history.length; i++) {
+      HistoryEntry historyEntry = state.history[i];
+      Widget content = historyEntry.route.build(this, historyEntry.route);
+      if (i == 0) {
+        visibleRoutes.add(content);
+        continue;
+      }
+      if (content == null)
+        continue;
+      Transition transition = new Transition(content: content)
+        ..direction = (i <= state.historyIndex) ? TransitionDirection.forward : TransitionDirection.reverse
+        ..interactive = (i == state.historyIndex)
+        ..onDismissed = () {
+        setState(() {
+          state.history.remove(historyEntry);
+        });
+      };
+      visibleRoutes.add(transition);
+    }
+    return new Stack(visibleRoutes);
   }
 }