Add custom curve when not dragging

@@ -8,6 +8,7 @@ import 'package:modal_bottom_sheet/modal_bottom_sheet.dart';
 class CupertinoSharePage extends StatelessWidget {
   @override
   Widget build(BuildContext context) {
+    
     return Scaffold(
         appBar: appBar(context),
         body: CupertinoPageScaffold(

@@ -162,6 +162,7 @@ class _MyHomePageState extends State<MyHomePage> {
                       title: Text('Cupertino Modal fit'),
                       onTap: () => showCupertinoModalBottomSheet(
                             expand: false,
+                    
                             context: context,
                             backgroundColor: Colors.transparent,
                             builder: (context, scrollController) =>
@@ -173,6 +174,7 @@ class _MyHomePageState extends State<MyHomePage> {
                       onTap: () => showCupertinoModalBottomSheet(
                             expand: true,
                             context: context,
+                            animationCurve: Curves.easeInOutCubic,
                             backgroundColor: Colors.transparent,
                             builder: (context, scrollController) =>
                                 ModalFit(scrollController: scrollController),

@@ -9,7 +9,7 @@ class NestedScrollModal extends StatelessWidget {
   @override
   Widget build(BuildContext context) {
     return NestedScrollView(
-      
+      controller: ScrollController(),
       physics: ScrollPhysics(parent: PageScrollPhysics()),
       headerSliverBuilder: (BuildContext context, bool innerBoxIsScrolled) {
         return <Widget>[
@@ -31,6 +31,7 @@ class NestedScrollModal extends StatelessWidget {
           );
         },
         itemCount: 12,
-        ));
+      ),
+    );
   }
 }

@@ -11,6 +11,12 @@ import 'package:flutter/material.dart';
 import 'package:flutter/scheduler.dart';
 import 'package:flutter/widgets.dart';
 
+import 'package:modal_bottom_sheet/src/utils/bottom_sheet_suspended_curve.dart';
+import 'package:modal_bottom_sheet/src/utils/primary_scroll_status_bar.dart';
+
+
+const Curve _decelerateEasing = Cubic(0.0, 0.0, 0.2, 1.0);
+const Curve _modalBottomSheetCurve = _decelerateEasing;
 const Duration _bottomSheetDuration = Duration(milliseconds: 400);
 const double _minFlingVelocity = 500.0;
 const double _closeProgressThreshold = 0.6;
@@ -61,7 +67,7 @@ class ModalBottomSheet extends StatefulWidget {
 
   /// The curve used by the animation showing and dismissing the bottom sheet.
   ///
-  /// If no curve is provided it falls back to `Curves.easeOutSine`.
+  /// If no curve is provided it falls back to `decelerateEasing`.
   final Curve animationCurve;
 
   /// Allows the bottom sheet to  go beyond the top bound of the content,
@@ -176,7 +182,10 @@ class _ModalBottomSheetState extends State<ModalBottomSheet>
     return result;
   }
 
+  ParametricCurve<double> animationCurve;
+
   void _handleDragUpdate(double primaryDelta) async {
+    animationCurve = Curves.linear;
     assert(widget.enableDrag, 'Dragging is disabled');
 
     if (_dismissUnderway) return;
@@ -210,6 +219,11 @@ class _ModalBottomSheetState extends State<ModalBottomSheet>
   void _handleDragEnd(double velocity) async {
     assert(widget.enableDrag, 'Dragging is disabled');
 
+    animationCurve = BottomSheetSuspendedCurve(
+      widget.animationController.value,
+      curve: _defaultCurve,
+    );
+
     if (_dismissUnderway || !isDragging) return;
     isDragging = false;
     _bounceDragController.reverse();
@@ -302,8 +316,12 @@ class _ModalBottomSheetState extends State<ModalBottomSheet>
     }
   }
 
+  ParametricCurve<double> get _defaultCurve =>
+      widget.animationCurve ?? _modalBottomSheetCurve;
+
   @override
   void initState() {
+    animationCurve = _defaultCurve;
     _bounceDragController =
         AnimationController(vsync: this, duration: Duration(milliseconds: 300));
     _scrollController = widget.scrollController ?? ScrollController();
@@ -328,19 +346,17 @@ class _ModalBottomSheetState extends State<ModalBottomSheet>
       );
     }
 
-    // Todo: Add curved Animation when push and pop without gesture
-    final Animation<double> containerAnimation = CurvedAnimation(
-      parent: widget.animationController,
-      curve: widget.animationCurve ?? Curves.linear,
-    );
+    final mediaQuery = MediaQuery.of(context);
 
-    return AnimatedBuilder(
+    child = AnimatedBuilder(
       animation: widget.animationController,
-      builder: (context, _) => ClipRect(
-        child: CustomSingleChildLayout(
-          delegate: _ModalBottomSheetLayout(
-              containerAnimation.value, widget.expanded),
-          child: !widget.enableDrag
+      builder: (context, child) {
+        final animationValue = animationCurve.transform(
+            mediaQuery.accessibleNavigation
+                ? 1.0
+                : widget.animationController.value);
+
+        final draggableChild = !widget.enableDrag
             ? child
             : KeyedSubtree(
                 key: _childKey,
@@ -349,10 +365,12 @@ class _ModalBottomSheetState extends State<ModalBottomSheet>
                   builder: (context, _) => CustomSingleChildLayout(
                     delegate: _CustomBottomSheetLayout(bounceAnimation.value),
                     child: GestureDetector(
-                        onVerticalDragUpdate: (details) =>
-                            _handleDragUpdate(details.primaryDelta),
-                        onVerticalDragEnd: (details) =>
-                            _handleDragEnd(details.primaryVelocity),
+                      onVerticalDragUpdate: (details) {
+                        _handleDragUpdate(details.primaryDelta);
+                      },
+                      onVerticalDragEnd: (details) {
+                        _handleDragEnd(details.primaryVelocity);
+                      },
                       child: NotificationListener<ScrollNotification>(
                         onNotification: (ScrollNotification notification) {
                           _handleScrollUpdate(notification);
@@ -363,10 +381,22 @@ class _ModalBottomSheetState extends State<ModalBottomSheet>
                     ),
                   ),
                 ),
+              );
+        return ClipRect(
+          child: CustomSingleChildLayout(
+            delegate: _ModalBottomSheetLayout(
+              animationValue,
+              widget.expanded,
             ),
+            child: draggableChild,
           ),
-      ),
         );
+      },
+      child: RepaintBoundary(child: child),
+    );
+
+    return PrimaryScrollStatusBarHandler(
+        scrollController: _scrollController, child: child);
   }
 }
 

+import 'dart:ui';
+
+import 'package:flutter/animation.dart';
+import 'package:flutter/foundation.dart';
+
+// Copied from bottom_sheet.dart as is a private class
+// https://github.com/flutter/flutter/issues/51627
+
+// TODO(guidezpl): Look into making this public. A copy of this class is in
+//  scaffold.dart, for now, https://github.com/flutter/flutter/issues/51627
+
+/// A curve that progresses linearly until a specified [startingPoint], at which
+/// point [curve] will begin. Unlike [Interval], [curve] will not start at zero,
+/// but will use [startingPoint] as the Y position.
+///
+/// For example, if [startingPoint] is set to `0.5`, and [curve] is set to
+/// [Curves.easeOut], then the bottom-left quarter of the curve will be a
+/// straight line, and the top-right quarter will contain the entire contents of
+/// [Curves.easeOut].
+///
+/// This is useful in situations where a widget must track the user's finger
+/// (which requires a linear animation), and afterwards can be flung using a
+/// curve specified with the [curve] argument, after the finger is released. In
+/// such a case, the value of [startingPoint] would be the progress of the
+/// animation at the time when the finger was released.
+///
+/// The [startingPoint] and [curve] arguments must not be null.
+class BottomSheetSuspendedCurve extends ParametricCurve<double> {
+  /// Creates a suspended curve.
+  const BottomSheetSuspendedCurve(
+    this.startingPoint, {
+    this.curve = Curves.easeOutCubic,
+  })  : assert(startingPoint != null),
+        assert(curve != null);
+
+  /// The progress value at which [curve] should begin.
+  ///
+  /// This defaults to [Curves.easeOutCubic].
+  final double startingPoint;
+
+  /// The curve to use when [startingPoint] is reached.
+  final Curve curve;
+
+  @override
+  double transform(double t) {
+    assert(t >= 0.0 && t <= 1.0);
+    assert(startingPoint >= 0.0 && startingPoint <= 1.0);
+
+    if (t < startingPoint) {
+      return t;
+    }
+
+    if (t == 1.0) {
+      return t;
+    }
+
+    final double curveProgress = (t - startingPoint) / (1 - startingPoint);
+    final double transformed = curve.transform(curveProgress);
+    return lerpDouble(startingPoint, 1, transformed);
+  }
+
+  @override
+  String toString() {
+    return '${describeIdentity(this)}($startingPoint, $curve)';
+  }
+}