Persistent Header Adaptive

A Flutter package that provides a SliverPersistentHeader with adaptive height capabilities, automatically adjusting to its content's size without requiring a fixed height.

Features

• Create SliverPersistentHeader widgets without specifying fixed heights
• Automatically adapts to the height of its content
• Supports both pinned and floating headers
• Compatible with CustomScrollView and other sliver-based scrolling widgets
• Optimized for smooth rendering and performance

Installation

Add this package to your pubspec.yaml file:

dependencies:
  persistent_header_adaptive: ^2.1.2

Run the install command:

flutter pub get

Usage

Basic Implementation

First, create your header widget:

class Header extends StatelessWidget {
  const Header({super.key});

  @override
  Widget build(BuildContext context) {
    return Container(
      padding: const EdgeInsets.all(20),
      color: Colors.grey,
      child: Column(
        mainAxisSize: MainAxisSize.min,
        children: [
          const Text('line 1'),
          const SizedBox(height: 20),
          Row(
            mainAxisAlignment: MainAxisAlignment.spaceEvenly,
            children: const [
              Text('line 2.1'),
              Text('line 2.2'),
            ],
          ),
          const SizedBox(height: 20),
          ElevatedButton(
            onPressed: () {},
            child: const Text('button'),
          ),
        ],
      ),
    );
  }
}

Then use AdaptiveHeightSliverPersistentHeader in a CustomScrollView:

class _HomepageState extends State<Homepage> {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: SafeArea(
        child: CustomScrollView(
          slivers: [
            const AdaptiveHeightSliverPersistentHeader(
              child: Header(),
              floating: true,
              needRepaint: true,
            ),
            SliverList(
              delegate: SliverChildBuilderDelegate(
                (context, index) => Card(
                  margin: const EdgeInsets.all(20),
                  child: Padding(
                    padding: const EdgeInsets.all(20.0),
                    child: Text('card $index'),
                  ),
                ),
                childCount: 100,
              ),
            )
          ],
        ),
      ),
    );
  }
}

Parameters

The AdaptiveHeightSliverPersistentHeader widget supports the following parameters:

Parameter	Type	Default	Description
child	Widget	required	The widget to display as the header
pinned	bool	false	Whether the header should remain visible at the start of the viewport
floating	bool	false	Whether the header should become visible when scrolling up even when not at top
needRepaint	bool	false	Whether the header should repaint on rebuild
initialHeight	double	0.0	Initial height to use before the widget's actual height is calculated

How It Works

AdaptiveHeightSliverPersistentHeader uses a combination of SizeReportingWidget and OverflowBox to:

1. Render the child widget without height constraints
2. Measure the resulting rendered size
3. Update the sliver's height to match the content's height
4. Trigger a layout update when the content size changes

This approach eliminates the need to manually specify heights for header widgets while ensuring proper layout and scrolling behavior.

Examples

Pinned Header

AdaptiveHeightSliverPersistentHeader(
  pinned: true,
  child: MyHeaderWidget(),
)

Floating Header

AdaptiveHeightSliverPersistentHeader(
  floating: true,
  child: MyHeaderWidget(),
)

With Initial Height

AdaptiveHeightSliverPersistentHeader(
  initialHeight: 100, // Initial height guess for better performance
  floating: true,
  child: MyHeaderWidget(),
)

Performance Considerations

For optimal performance:

• Set a reasonable initialHeight if you can approximate the header's height
• Use needRepaint: false when the header content rarely changes
• Apply appropriate keys to header widgets to preserve state when appropriate

Contributing

Contributions are welcome! If you find a bug or want to add a feature, please file an issue or submit a pull request on the GitHub repository.

License

This package is available under the MIT License.