Dismissable component

sky/sdk/example/widgets/card_collection.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 'dart:sky' as sky;
-
-import 'package:vector_math/vector_math.dart';
-import 'package:sky/animation/animation_performance.dart';
 import 'package:sky/base/lerp.dart';
 import 'package:sky/painting/text_style.dart';
 import 'package:sky/theme/colors.dart';
-import 'package:sky/widgets/animation_builder.dart';
 import 'package:sky/widgets/basic.dart';
 import 'package:sky/widgets/card.dart';
+import 'package:sky/widgets/dismissable.dart';
 import 'package:sky/widgets/scaffold.dart';
 import 'package:sky/widgets/variable_height_scrollable.dart';
 import 'package:sky/widgets/theme.dart';
 import 'package:sky/widgets/tool_bar.dart';
 import 'package:sky/widgets/widget.dart';
 
 
-const int _kCardDismissFadeoutMS = 300;
-const double _kMinFlingVelocity = 700.0;
-const double _kMinFlingVelocityDelta = 400.0;
-const double _kDismissCardThreshold = 0.6;
-
 class CardCollectionApp extends App {
 
   final TextStyle cardLabelStyle =
     new TextStyle(color: White, fontSize: 18.0, fontWeight: bold);
 
   final List<double> cardHeights = [
     48.0, 64.0, 82.0, 46.0, 60.0, 55.0, 84.0, 96.0, 50.0,
     48.0, 64.0, 82.0, 46.0, 60.0, 55.0, 84.0, 96.0, 50.0,
     48.0, 64.0, 82.0, 46.0, 60.0, 55.0, 84.0, 96.0, 50.0,
     48.0, 64.0, 82.0, 46.0, 60.0, 55.0, 84.0, 96.0, 50.0
   ];
 
   List<int> visibleCardIndices;
 
-  CardCollectionApp() {
-    _activeCardTransform = new AnimationBuilder()
-      ..position = new AnimatedType<Point>(Point.origin)
-      ..opacity = new AnimatedType<double>(1.0, end: 0.0);
-
-    _activeCardAnimation = _activeCardTransform.createPerformance(
-        [_activeCardTransform.position, _activeCardTransform.opacity],
-        duration: new Duration(milliseconds: _kCardDismissFadeoutMS));
-    _activeCardAnimation.addListener(_handleAnimationProgressChanged);
-
+  void initState() {
     visibleCardIndices = new List.generate(cardHeights.length, (i) => i);
+    super.initState();
   }
 
-  int _activeCardIndex = -1;
-  AnimationBuilder _activeCardTransform;
-  AnimationPerformance _activeCardAnimation;
-  double _activeCardWidth;
-  double _activeCardDragX = 0.0;
-  bool _activeCardDragUnderway = false;
-
-  Point get _activeCardDragEndPoint {
-    return new Point(_activeCardDragX.sign * _activeCardWidth * _kDismissCardThreshold, 0.0);
-  }
-
-  void _handleAnimationProgressChanged() {
+  void dismissCard(int cardIndex) {
     setState(() {
-      if (_activeCardAnimation.isCompleted && !_activeCardDragUnderway)
-        visibleCardIndices.remove(_activeCardIndex);
+      visibleCardIndices.remove(cardIndex);
     });
   }
 
-  void _handleSizeChanged(Size newSize) {
-    _activeCardWidth = newSize.width;
-    _activeCardTransform.position.end = _activeCardDragEndPoint;
-  }
-
-  void _handlePointerDown(sky.PointerEvent event, int cardIndex) {
-    setState(() {
-      _activeCardIndex = cardIndex;
-      _activeCardDragUnderway = true;
-      _activeCardDragX = 0.0;
-      _activeCardAnimation.progress = 0.0;
-    });
-  }
-
-  void _handlePointerMove(sky.PointerEvent event) {
-    if (_activeCardWidth == null || _activeCardIndex < 0)
-      return;
-
-    double oldDragX = _activeCardDragX;
-    _activeCardDragX += event.dx;
-    setState(() {
-      if (!_activeCardAnimation.isAnimating) {
-        if (oldDragX.sign != _activeCardDragX.sign)
-          _activeCardTransform.position.end = _activeCardDragEndPoint;
-        _activeCardAnimation.progress = _activeCardDragX.abs() / (_activeCardWidth * _kDismissCardThreshold);
-      }
-    });
-  }
-
-  void _handlePointerUpOrCancel(_) {
-    if (_activeCardWidth == null || _activeCardIndex < 0)
-      return;
-
-    setState(() {
-      _activeCardDragUnderway = false;
-      if (_activeCardAnimation.isCompleted)
-        visibleCardIndices.remove(_activeCardIndex);
-      else if (!_activeCardAnimation.isAnimating)
-        _activeCardAnimation.progress = 0.0;
-    });
-  }
-
-  bool _isHorizontalFlingGesture(sky.GestureEvent event) {
-    double vx = event.velocityX.abs();
-    double vy = event.velocityY.abs();
-    return vx - vy > _kMinFlingVelocityDelta && vx > _kMinFlingVelocity;
-  }
-
-  void _handleFlingStart(sky.GestureEvent event) {
-    if (_activeCardWidth == null || _activeCardIndex < 0)
-      return;
-
-    _activeCardDragUnderway = false;
-
-    if (_isHorizontalFlingGesture(event)) {
-      double distance = 1.0 - _activeCardAnimation.progress;
-      if (distance > 0.0) {
-        double duration = 250.0 * 1000.0 * distance / event.velocityX.abs();
-        _activeCardDragX = event.velocityX.sign;
-        _activeCardAnimation.timeline.animateTo(1.0, duration: duration);
-      }
-    }
-  }
-
-  Widget _buildCard(int cardIndex) {
-    Widget label = new Center(child: new Text("Item ${cardIndex}", style: cardLabelStyle));
-    Color color = lerpColor(Red[500], Blue[500], cardIndex / cardHeights.length);
-    Widget card = new Card(
-      child: new Padding(child: label, padding: const EdgeDims.all(8.0)),
-      color: color
-    );
-
-    // TODO(hansmuller) The code below changes the card's widget tree when
-    // the user starts dragging it. Currently this causes Sky to drop the
-    // rest of the pointer gesture, see https://github.com/domokit/mojo/issues/312.
-    // As a workaround, always create the Transform and Opacity nodes.
-    if (cardIndex == _activeCardIndex) {
-      card = _activeCardTransform.build(card);
-    } else {
-      card = new Transform(child: card, transform: new Matrix4.identity());
-      card = new Opacity(child: card, opacity: 1.0);
-    }
-
-    return new Listener(
-      key: "$cardIndex",
-      child: new Container(child: card, height: cardHeights[cardIndex]),
-      onPointerDown: (event) { _handlePointerDown(event, cardIndex); },
-      onPointerMove: _handlePointerMove,
-      onPointerUp: _handlePointerUpOrCancel,
-      onPointerCancel: _handlePointerUpOrCancel,
-      onGestureFlingStart: _handleFlingStart
-    );
-  }
-
   Widget _builder(int index) {
     if (index >= visibleCardIndices.length)
       return null;
-    return _buildCard(visibleCardIndices[index]);
+    
+    int cardIndex = visibleCardIndices[index];
+    Color color = lerpColor(Red[500], Blue[500], cardIndex / cardHeights.length);
+    Widget label = new Text("Item ${cardIndex}", style: cardLabelStyle);
+    return new Dismissable(
+      key: cardIndex.toString(),
+      onDismissed: () { dismissCard(cardIndex); },
+      child: new Card(
+        color: color,
+        child: new Container(
+          height: cardHeights[cardIndex],
+          padding: const EdgeDims.all(8.0),
+          child: new Center(child: label)
+        )
+      )
+    );
   }
 
   Widget build() {
     Widget cardCollection = new Container(
       padding: const EdgeDims.symmetric(vertical: 12.0, horizontal: 8.0),
       decoration: new BoxDecoration(backgroundColor: Theme.of(this).primarySwatch[50]),
       child: new VariableHeightScrollable(
         builder: _builder,
         token: visibleCardIndices.length
       )
     );
 
     return new Scaffold(
       toolbar: new ToolBar(center: new Text('Swipe Away')),
-      body: new SizeObserver(child: cardCollection, callback: _handleSizeChanged)
+      body: cardCollection
     );
   }
 }
 
 void main() {
   runApp(new CardCollectionApp());
 }