Partially viewable bottom sheet - flutter

Use the DraggableScrollableSheet widget with the Stack widget:

Here's the gist for the entire page in this^ GIF, or try the Codepen.

Here's the structure of the entire page:

  @override  Widget build(BuildContext context) {    return Scaffold(      body: Stack(        children: <Widget>[          CustomGoogleMap(),          CustomHeader(),          DraggableScrollableSheet(            initialChildSize: 0.30,            minChildSize: 0.15,            builder: (BuildContext context, ScrollController scrollController) {              return SingleChildScrollView(                controller: scrollController,                child: CustomScrollViewContent(),              );            },          ),        ],      ),    );  }

In the Stack:
- The Google map is the lower most layer.
- The Header (search field + horizontally scrolling chips) is above the map.
- The DraggableBottomSheet is above the Header.

Some useful parameters as defined in draggable_scrollable_sheet.dart:

  /// The initial fractional value of the parent container's height to use when  /// displaying the widget.  ///  /// The default value is `0.5`.  final double initialChildSize;  /// The minimum fractional value of the parent container's height to use when  /// displaying the widget.  ///  /// The default value is `0.25`.  final double minChildSize;  /// The maximum fractional value of the parent container's height to use when  /// displaying the widget.  ///  /// The default value is `1.0`.  final double maxChildSize;

Edit: Thank you @Alejandro for pointing out the typo in the widget name :)

I will be implementing the same behaviour in the next few weeks and I will be referring to the backdrop implementation in Flutter Gallery, I was able to modify it previously to swipe to display and hide (with a peek area).

To be precise you can replicate the desired effect by changing this line of code in backdrop_demo.dart from Flutter Gallery :

 void _handleDragUpdate(DragUpdateDetails details) {    if (_controller.isAnimating)// || _controller.status == AnimationStatus.completed)      return;    _controller.value -= details.primaryDelta / (_backdropHeight ?? details.primaryDelta); }

I have just commented the controller status check to allow the panel to be swipe-able.

I know this isn't the complete implementation you are looking for, but I hope this helps you in any way.