Add transitionBackgroundColor

Allow to customize backaground color behind all views animated by CupertinoModalBottomSheetRoute

@@ -84,6 +84,7 @@ Future<T> showCupertinoModalBottomSheet<T>({
   Radius topRadius = _default_top_radius,
   Duration duration,
   RouteSettings settings,
+  Color transitionBackgroundColor,
 }) async {
   assert(context != null);
   assert(builder != null);
@@ -121,6 +122,7 @@ Future<T> showCupertinoModalBottomSheet<T>({
     previousRouteAnimationCurve: previousRouteAnimationCurve,
     duration: duration,
     settings: settings,
+    transitionBackgroundColor: transitionBackgroundColor ?? Colors.black
   ));
   return result;
 }
@@ -129,6 +131,10 @@ class CupertinoModalBottomSheetRoute<T> extends ModalBottomSheetRoute<T> {
   final Radius topRadius;
   final Curve previousRouteAnimationCurve;
 
+  // Background color behind all routes
+  // Black by default
+  final Color transitionBackgroundColor;
+
   CupertinoModalBottomSheetRoute({
     ScrollWidgetBuilder builder,
     WidgetWithChildBuilder containerBuilder,
@@ -145,6 +151,7 @@ class CupertinoModalBottomSheetRoute<T> extends ModalBottomSheetRoute<T> {
     @required bool expanded,
     Duration duration,
     RouteSettings settings,
+    this.transitionBackgroundColor,
     this.topRadius = _default_top_radius,
     this.previousRouteAnimationCurve,
   })  : assert(expanded != null),
@@ -199,6 +206,7 @@ class CupertinoModalBottomSheetRoute<T> extends ModalBottomSheetRoute<T> {
       body: child,
       animationCurve: previousRouteAnimationCurve,
       topRadius: topRadius,
+      backgroundColor: transitionBackgroundColor ?? Colors.black,
     );
   }
 }
@@ -207,6 +215,7 @@ class _CupertinoModalTransition extends StatelessWidget {
   final Animation<double> secondaryAnimation;
   final Radius topRadius;
   final Curve animationCurve;
+  final Color backgroundColor;
 
   final Widget body;
 
@@ -215,6 +224,7 @@ class _CupertinoModalTransition extends StatelessWidget {
     @required this.secondaryAnimation,
     @required this.body,
     @required this.topRadius,
+    this.backgroundColor = Colors.black,
     this.animationCurve,
   }) : super(key: key);
 
@@ -246,7 +256,7 @@ class _CupertinoModalTransition extends StatelessWidget {
                 : (1 - progress) * startRoundCorner + progress * topRadius.x;
             return Stack(
               children: <Widget>[
-                Container(color: Colors.black),
+                Container(color: backgroundColor),
                 Transform.translate(
                   offset: Offset(0, yOffset),
                   child: Transform.scale(
@@ -266,6 +276,7 @@ class _CupertinoModalTransition extends StatelessWidget {
 
 class _CupertinoScaffold extends InheritedWidget {
   final AnimationController animation;
+
   final Radius topRadius;
 
   @override
@@ -288,10 +299,14 @@ class CupertinoScaffold extends StatefulWidget {
 
   final Widget body;
   final Radius topRadius;
+  final Color transitionBackgroundColor;
 
-  const CupertinoScaffold(
-      {Key key, this.body, this.topRadius = _default_top_radius})
-      : super(key: key);
+  const CupertinoScaffold({
+    Key key,
+    this.body,
+    this.topRadius = _default_top_radius,
+    this.transitionBackgroundColor = Colors.black,
+  }) : super(key: key);
 
   @override
   State<StatefulWidget> createState() => _CupertinoScaffoldState();
@@ -376,6 +391,7 @@ class _CupertinoScaffoldState extends State<CupertinoScaffold>
         secondaryAnimation: animationController,
         body: widget.body,
         topRadius: widget.topRadius,
+        backgroundColor: widget.transitionBackgroundColor,
       ),
     );
   }

 # Generated by pub
 # See https://dart.dev/tools/pub/glossary#lockfile
 packages:
-  archive:
-    dependency: transitive
-    description:
-      name: archive
-      url: "https://pub.dartlang.org"
-    source: hosted
-    version: "2.0.13"
-  args:
-    dependency: transitive
-    description:
-      name: args
-      url: "https://pub.dartlang.org"
-    source: hosted
-    version: "1.6.0"
   async:
     dependency: transitive
     description:
@@ -29,6 +15,13 @@ packages:
       url: "https://pub.dartlang.org"
     source: hosted
     version: "2.0.0"
+  characters:
+    dependency: transitive
+    description:
+      name: characters
+      url: "https://pub.dartlang.org"
+    source: hosted
+    version: "1.0.0"
   charcode:
     dependency: transitive
     description:
@@ -36,27 +29,27 @@ packages:
       url: "https://pub.dartlang.org"
     source: hosted
     version: "1.1.3"
-  collection:
+  clock:
     dependency: transitive
     description:
-      name: collection
+      name: clock
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.14.12"
-  convert:
+    version: "1.0.1"
+  collection:
     dependency: transitive
     description:
-      name: convert
+      name: collection
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "2.1.1"
-  crypto:
+    version: "1.14.13"
+  fake_async:
     dependency: transitive
     description:
-      name: crypto
+      name: fake_async
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "2.1.4"
+    version: "1.1.0"
   flutter:
     dependency: "direct main"
     description: flutter
@@ -67,20 +60,13 @@ packages:
     description: flutter
     source: sdk
     version: "0.0.0"
-  image:
-    dependency: transitive
-    description:
-      name: image
-      url: "https://pub.dartlang.org"
-    source: hosted
-    version: "2.1.12"
   matcher:
     dependency: transitive
     description:
       name: matcher
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "0.12.6"
+    version: "0.12.8"
   meta:
     dependency: transitive
     description:
@@ -94,28 +80,14 @@ packages:
       name: path
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.6.4"
+    version: "1.7.0"
   pedantic:
     dependency: "direct dev"
     description:
       name: pedantic
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.8.0+1"
-  petitparser:
-    dependency: transitive
-    description:
-      name: petitparser
-      url: "https://pub.dartlang.org"
-    source: hosted
-    version: "2.4.0"
-  quiver:
-    dependency: transitive
-    description:
-      name: quiver
-      url: "https://pub.dartlang.org"
-    source: hosted
-    version: "2.1.3"
+    version: "1.9.0"
   sky_engine:
     dependency: transitive
     description: flutter
@@ -162,7 +134,7 @@ packages:
       name: test_api
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "0.2.15"
+    version: "0.2.17"
   typed_data:
     dependency: transitive
     description:
@@ -177,13 +149,6 @@ packages:
       url: "https://pub.dartlang.org"
     source: hosted
     version: "2.0.8"
-  xml:
-    dependency: transitive
-    description:
-      name: xml
-      url: "https://pub.dartlang.org"
-    source: hosted
-    version: "3.6.1"
 sdks:
-  dart: ">=2.6.0 <3.0.0"
+  dart: ">=2.9.0-14.0.dev <3.0.0"
   flutter: ">=1.12.0 <2.0.0"