adds properties to dismissible widget (#14162)

* adds crossAxisEndOffset and rollbackDuration properties to dismissible widget

* re-added removed license comment

* corrected license comments

* Adds test for rollbackDuration and crossAxisEndOffset

* added tests and comments

* modified tests for dismissible widgets

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

@@ -12,7 +12,6 @@ import 'gesture_detector.dart';
 import 'ticker_provider.dart';
 import 'transitions.dart';
 
-const Duration _kDismissDuration = const Duration(milliseconds: 200);
 const Curve _kResizeTimeCurve = const Interval(0.4, 1.0, curve: Curves.ease);
 const double _kMinFlingVelocity = 700.0;
 const double _kMinFlingVelocityDelta = 400.0;
@@ -83,6 +82,8 @@ class Dismissible extends StatefulWidget {
     this.direction: DismissDirection.horizontal,
     this.resizeDuration: const Duration(milliseconds: 300),
     this.dismissThresholds: const <DismissDirection, double>{},
+    this.movementDuration: const Duration(milliseconds: 200),
+    this.crossAxisEndOffset: 0.0,
   }) : assert(key != null),
        assert(secondaryBackground != null ? background != null : true),
        super(key: key);
@@ -134,6 +135,15 @@ class Dismissible extends StatefulWidget {
   /// [direction] property.
   final Map<DismissDirection, double> dismissThresholds;
 
+  /// Defines the duration for card to dismiss or to come back to original position if not dismissed.
+  final Duration movementDuration;
+
+  /// Defines the end offset across the main axis after the card is dismissed.
+  ///
+  /// If non-zero value is given then widget moves in cross direction depending on whether
+  /// it is positive or negative.
+  final double crossAxisEndOffset;
+
   @override
   _DismissibleState createState() => new _DismissibleState();
 }
@@ -183,7 +193,7 @@ class _DismissibleState extends State<Dismissible> with TickerProviderStateMixin
   @override
   void initState() {
     super.initState();
-    _moveController = new AnimationController(duration: _kDismissDuration, vsync: this)
+    _moveController = new AnimationController(duration: widget.movementDuration, vsync: this)
       ..addStatusListener(_handleDismissStatusChanged);
     _updateMoveAnimation();
   }
@@ -317,7 +327,9 @@ class _DismissibleState extends State<Dismissible> with TickerProviderStateMixin
     final double end = _dragExtent.sign;
     _moveAnimation = new Tween<Offset>(
       begin: Offset.zero,
-      end: _directionIsXAxis ? new Offset(end, 0.0) : new Offset(0.0, end),
+      end: _directionIsXAxis
+          ? new Offset(end, widget.crossAxisEndOffset)
+          : new Offset(widget.crossAxisEndOffset, end),
     ).animate(_moveController);
   }
 
@@ -513,3 +525,4 @@ class _DismissibleState extends State<Dismissible> with TickerProviderStateMixin
     );
   }
 }
+

packages/flutter/test/widgets/dismissible_test.dart

@@ -13,6 +13,7 @@ DismissDirection dismissDirection = DismissDirection.horizontal;
 DismissDirection reportedDismissDirection;
 List<int> dismissedItems = <int>[];
 Widget background;
+const double crossAxisEndOffset = 0.5;
 
 Widget buildTest({ double startToEndThreshold, TextDirection textDirection: TextDirection.ltr }) {
   return new Directionality(
@@ -37,6 +38,7 @@ Widget buildTest({ double startToEndThreshold, TextDirection textDirection: Text
             dismissThresholds: startToEndThreshold == null
                 ? <DismissDirection, double>{}
                 : <DismissDirection, double>{DismissDirection.startToEnd: startToEndThreshold},
+            crossAxisEndOffset: crossAxisEndOffset,
             child: new Container(
               width: itemExtent,
               height: itemExtent,
@@ -143,6 +145,53 @@ Future<Null> dismissItem(WidgetTester tester, int item, {
   await tester.pump(); // rebuild after the callback removes the entry
 }
 
+Future<Null> checkFlingItemBeforeMovementEnd(WidgetTester tester, int item, {
+  @required AxisDirection gestureDirection,
+  DismissMethod mechanism: rollbackElement
+}) async {
+  assert(gestureDirection != null);
+  final Finder itemFinder = find.text(item.toString());
+  expect(itemFinder, findsOneWidget);
+
+  await mechanism(tester, itemFinder, gestureDirection: gestureDirection);
+
+  await tester.pump(); // start the slide
+  await tester.pump(const Duration(milliseconds: 100));
+}
+
+Future<Null> checkFlingItemAfterMovement(WidgetTester tester, int item, {
+  @required AxisDirection gestureDirection,
+  DismissMethod mechanism: rollbackElement
+}) async {
+  assert(gestureDirection != null);
+  final Finder itemFinder = find.text(item.toString());
+  expect(itemFinder, findsOneWidget);
+
+  await mechanism(tester, itemFinder, gestureDirection: gestureDirection);
+
+  await tester.pump(); // start the slide
+  await tester.pump(const Duration(milliseconds: 300));
+}
+
+Future<Null> rollbackElement(WidgetTester tester, Finder finder, { @required AxisDirection gestureDirection, double initialOffsetFactor: 0.0 }) async {
+  Offset delta;
+  switch (gestureDirection) {
+    case AxisDirection.left:
+      delta = const Offset(-30.0, 0.0);
+      break;
+    case AxisDirection.right:
+      delta = const Offset(30.0, 0.0);
+      break;
+    case AxisDirection.up:
+      delta = const Offset(0.0, -30.0);
+      break;
+    case AxisDirection.down:
+      delta = const Offset(0.0, 30.0);
+      break;
+  }
+  await tester.fling(finder, delta, 1000.0, initialOffset: delta * initialOffsetFactor);
+}
+
 class Test1215DismissibleWidget extends StatelessWidget {
   const Test1215DismissibleWidget(this.text);
 
@@ -558,4 +607,54 @@ void main() {
     final RenderBox backgroundBox = tester.firstRenderObject(find.text('background'));
     expect(backgroundBox.size.height, equals(100.0));
   });
-}
+
+  testWidgets('Checking fling item before movementDuration completes', (WidgetTester tester) async {
+    await tester.pumpWidget(buildTest());
+    expect(dismissedItems, isEmpty);
+
+    await checkFlingItemBeforeMovementEnd(tester, 0, gestureDirection: AxisDirection.left, mechanism: flingElement);
+    expect(find.text('0'), findsOneWidget);
+
+    await checkFlingItemBeforeMovementEnd(tester, 1, gestureDirection: AxisDirection.right, mechanism: flingElement);
+    expect(find.text('1'), findsOneWidget);
+  });
+
+  testWidgets('Checking fling item  after movementDuration', (WidgetTester tester) async {
+    await tester.pumpWidget(buildTest());
+    expect(dismissedItems, isEmpty);
+
+    await checkFlingItemAfterMovement(tester, 1, gestureDirection: AxisDirection.left, mechanism: flingElement);
+    expect(find.text('1'), findsNothing);
+
+    await checkFlingItemAfterMovement(tester, 0, gestureDirection: AxisDirection.right, mechanism: flingElement);
+    expect(find.text('0'), findsNothing);
+  });
+
+  testWidgets('Horizontal fling less than threshold', (WidgetTester tester) async {
+    scrollDirection = Axis.horizontal;
+    await tester.pumpWidget(buildTest());
+    expect(dismissedItems, isEmpty);
+
+    await checkFlingItemAfterMovement(tester, 0, gestureDirection: AxisDirection.left, mechanism: rollbackElement);
+    expect(find.text('0'), findsOneWidget);
+    expect(dismissedItems, isEmpty);
+
+    await checkFlingItemAfterMovement(tester, 1, gestureDirection: AxisDirection.right, mechanism: rollbackElement);
+    expect(find.text('1'), findsOneWidget);
+    expect(dismissedItems, isEmpty);
+  });
+
+  testWidgets('Vertical fling less than threshold', (WidgetTester tester) async {
+    scrollDirection = Axis.vertical;
+    await tester.pumpWidget(buildTest());
+    expect(dismissedItems, isEmpty);
+
+    await checkFlingItemAfterMovement(tester, 0, gestureDirection: AxisDirection.left, mechanism: rollbackElement);
+    expect(find.text('0'), findsOneWidget);
+    expect(dismissedItems, isEmpty);
+
+    await checkFlingItemAfterMovement(tester, 1, gestureDirection: AxisDirection.right, mechanism: rollbackElement);
+    expect(find.text('1'), findsOneWidget);
+    expect(dismissedItems, isEmpty);
+  });
+}
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