Change RawGestureDetector API to be better for strong mode Dart. (#10553)

dev/manual_tests/lib/material_arc.dart

@@ -189,10 +189,13 @@ class _PointDemoState extends State<_PointDemo> {
     return new RawGestureDetector(
       behavior: _dragTarget == null ? HitTestBehavior.deferToChild : HitTestBehavior.opaque,
       gestures: <Type, GestureRecognizerFactory>{
-        ImmediateMultiDragGestureRecognizer: (ImmediateMultiDragGestureRecognizer recognizer) { // ignore: map_value_type_not_assignable, https://github.com/flutter/flutter/issues/5771
-          return (recognizer ??= new ImmediateMultiDragGestureRecognizer())
-            ..onStart = _handleOnStart;
-        }
+        ImmediateMultiDragGestureRecognizer: new GestureRecognizerFactoryWithHandlers<ImmediateMultiDragGestureRecognizer>(
+          () => new ImmediateMultiDragGestureRecognizer(),
+          (ImmediateMultiDragGestureRecognizer instance) {
+            instance
+              ..onStart = _handleOnStart;
+          },
+        ),
       },
       child: new ClipRect(
         child: new CustomPaint(
@@ -359,10 +362,13 @@ class _RectangleDemoState extends State<_RectangleDemo> {
     return new RawGestureDetector(
       behavior: _dragTarget == null ? HitTestBehavior.deferToChild : HitTestBehavior.opaque,
       gestures: <Type, GestureRecognizerFactory>{
-        ImmediateMultiDragGestureRecognizer: (ImmediateMultiDragGestureRecognizer recognizer) { // ignore: map_value_type_not_assignable, https://github.com/flutter/flutter/issues/5771
-          return (recognizer ??= new ImmediateMultiDragGestureRecognizer())
-            ..onStart = _handleOnStart;
-        }
+        ImmediateMultiDragGestureRecognizer: new GestureRecognizerFactoryWithHandlers<ImmediateMultiDragGestureRecognizer>(
+          () => new ImmediateMultiDragGestureRecognizer(),
+          (ImmediateMultiDragGestureRecognizer instance) {
+            instance
+              ..onStart = _handleOnStart;
+          },
+        ),
       },
       child: new ClipRect(
         child: new CustomPaint(

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

@@ -721,18 +721,22 @@ class ScaffoldState extends State<Scaffold> with TickerProviderStateMixin {
   NavigationGestureController _backGestureController;
 
   bool _shouldHandleBackGesture() {
+    assert(mounted);
     return Theme.of(context).platform == TargetPlatform.iOS && Navigator.canPop(context);
   }
 
   void _handleDragStart(DragStartDetails details) {
+    assert(mounted);
     _backGestureController = Navigator.of(context).startPopGesture();
   }
 
   void _handleDragUpdate(DragUpdateDetails details) {
+    assert(mounted);
     _backGestureController?.dragUpdate(details.primaryDelta / context.size.width);
   }
 
   void _handleDragEnd(DragEndDetails details) {
+    assert(mounted);
     final bool willPop = _backGestureController?.dragEnd(details.velocity.pixelsPerSecond.dx / context.size.width) ?? false;
     if (willPop)
       _currentBottomSheet?.close();
@@ -740,6 +744,7 @@ class ScaffoldState extends State<Scaffold> with TickerProviderStateMixin {
   }
 
   void _handleDragCancel() {
+    assert(mounted);
     final bool willPop = _backGestureController?.dragEnd(0.0) ?? false;
     if (willPop)
       _currentBottomSheet?.close();

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

@@ -327,32 +327,38 @@ class ScrollableState extends State<Scrollable> with TickerProviderStateMixin
       switch (widget.axis) {
         case Axis.vertical:
           _gestureRecognizers = <Type, GestureRecognizerFactory>{
-            VerticalDragGestureRecognizer: (VerticalDragGestureRecognizer recognizer) {  // ignore: map_value_type_not_assignable, https://github.com/flutter/flutter/issues/7173
-              return (recognizer ??= new VerticalDragGestureRecognizer())
-                ..onDown = _handleDragDown
-                ..onStart = _handleDragStart
-                ..onUpdate = _handleDragUpdate
-                ..onEnd = _handleDragEnd
-                ..onCancel = _handleDragCancel
-                ..minFlingDistance = _physics?.minFlingDistance
-                ..minFlingVelocity = _physics?.minFlingVelocity
-                ..maxFlingVelocity = _physics?.maxFlingVelocity;
-            }
+            VerticalDragGestureRecognizer: new GestureRecognizerFactoryWithHandlers<VerticalDragGestureRecognizer>(
+              () => new VerticalDragGestureRecognizer(),
+              (VerticalDragGestureRecognizer instance) {
+                instance
+                  ..onDown = _handleDragDown
+                  ..onStart = _handleDragStart
+                  ..onUpdate = _handleDragUpdate
+                  ..onEnd = _handleDragEnd
+                  ..onCancel = _handleDragCancel
+                  ..minFlingDistance = _physics?.minFlingDistance
+                  ..minFlingVelocity = _physics?.minFlingVelocity
+                  ..maxFlingVelocity = _physics?.maxFlingVelocity;
+              },
+            ),
           };
           break;
         case Axis.horizontal:
           _gestureRecognizers = <Type, GestureRecognizerFactory>{
-            HorizontalDragGestureRecognizer: (HorizontalDragGestureRecognizer recognizer) {  // ignore: map_value_type_not_assignable, https://github.com/flutter/flutter/issues/7173
-              return (recognizer ??= new HorizontalDragGestureRecognizer())
-                ..onDown = _handleDragDown
-                ..onStart = _handleDragStart
-                ..onUpdate = _handleDragUpdate
-                ..onEnd = _handleDragEnd
-                ..onCancel = _handleDragCancel
-                ..minFlingDistance = _physics?.minFlingDistance
-                ..minFlingVelocity = _physics?.minFlingVelocity
-                ..maxFlingVelocity = _physics?.maxFlingVelocity;
-            }
+            HorizontalDragGestureRecognizer: new GestureRecognizerFactoryWithHandlers<HorizontalDragGestureRecognizer>(
+              () => new HorizontalDragGestureRecognizer(),
+              (HorizontalDragGestureRecognizer instance) {
+                instance
+                  ..onDown = _handleDragDown
+                  ..onStart = _handleDragStart
+                  ..onUpdate = _handleDragUpdate
+                  ..onEnd = _handleDragEnd
+                  ..onCancel = _handleDragCancel
+                  ..minFlingDistance = _physics?.minFlingDistance
+                  ..minFlingVelocity = _physics?.minFlingVelocity
+                  ..maxFlingVelocity = _physics?.maxFlingVelocity;
+              },
+            ),
           };
           break;
       }