How to use Flutter to build a bottom sheet widget which is able to drag up to full screen?

Question

I want to build a bottom sheet widget which is able to drag up to full screen.

Can anyone tell me how to do this?

Google map has a widget is able to do this. Here is the screenshot (check attached image):

Before drag up:

After drag up:

Answer 1

Use the DraggableBottomSheet 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;