The official BottomAppBar can only display a notch FAB with app bar, sometimes we need a convex FAB. This ConvexAppBar is inspired by BottomAppBar and NotchShape’s implementation.

Online example can be found at https://appbar.codemagic.app.

convex_bottom_bar is now a Flutter Favorite package!

Here are some supported style:

fixed	react	badge chip
fixedCircle	reactCircle	flip
textIn	titled	tab image
button	fixed corner

How to use

Typically ConvexAppBar can work with Scaffold by setup its bottomNavigationBar.

The ConvexAppBar has to two constructors, the ConvexAppBar() will use default style to simplify the tab creation.

Add this to your package’s pubspec.yaml file, use the latest version :

dependencies:
  convex_bottom_bar: ^latest_version

import 'package:convex_bottom_bar/convex_bottom_bar.dart';

Scaffold(
  bottomNavigationBar: ConvexAppBar(
    items: [
      TabItem(icon: Icons.home, title: 'Home'),
      TabItem(icon: Icons.map, title: 'Discovery'),
      TabItem(icon: Icons.add, title: 'Add'),
      TabItem(icon: Icons.message, title: 'Message'),
      TabItem(icon: Icons.people, title: 'Profile'),
    ],
    initialActiveIndex: 2,//optional, default as 0
    onTap: (int i) => print('click index=$i'),
  )
);

Flutter Version Support
As Flutter is developing fast. There can be breaking changes, we will trying to support the stable version and beta version through different package version.

Features

• Provide multiple internal styles
• Ability to change the theme of AppBar
• Provide builder API to customize new style
• Add badge on tab menu
• Elegant transition animation
• Provide hook API to override some of internal styles
• RTL support

Table of contents

• Theming
• Badge
• Single Button
• Style Hook
• RTL Support
• Custom Example
• FAQ

Theming

The bar will use default style, you may want to theme it. Here are some supported attributes:

Badge

If you need to add badge on the tab, use ConvexAppBar.badge to get it done.

ConvexAppBar.badge({0: '99+', 1: Icons.assistant_photo, 2: Colors.redAccent},
  items: [
    TabItem(icon: Icons.home, title: 'Home'),
    TabItem(icon: Icons.map, title: 'Discovery'),
    TabItem(icon: Icons.add, title: 'Add'),
  ],
  onTap: (int i) => print('click index=$i'),
);

The badge() method accept an array of badges; The badges is map with tab items, each value of entry can be either String, IconData, Color or Widget.

Single Button

If you only need a single button, checkout the ConvexButton.

Scaffold(
  appBar: AppBar(title: const Text('ConvexButton Example')),
  body: Center(child: Text('count $count')),
  bottomNavigationBar: ConvexButton.fab(
    onTap: () => setState(() => count++),
  ),
);

Style Hook

Hook for internal tab style. Unlike the ConvexAppBar.builder, you may want to update the tab style without define a new tab style.

Warning:
This hook is limited, and can lead to overflow broken if the size you provide does no match with internal style.

StyleProvider(
  style: Style(),
  child: ConvexAppBar(
    initialActiveIndex: 1,
    height: 50,
    top: -30,
    curveSize: 100,
    style: TabStyle.fixedCircle,
    items: [
      TabItem(icon: Icons.link),
      TabItem(icon: Icons.import_contacts),
      TabItem(title: "2020", icon: Icons.work),
    ],
    backgroundColor: _tabBackgroundColor,
  ),
)
class Style extends StyleHook {
  @override
  double get activeIconSize => 40;

  @override
  double get activeIconMargin => 10;

  @override
  double get iconSize => 20;

  @override
  TextStyle textStyle(Color color) {
    return TextStyle(fontSize: 20, color: color);
  }
}

RTL Support

RTL is supported internally, if you define the TextDirection inside app, the AppBar should work fine. Both RTL and LTR can be configured through Directionality:

Directionality(
  textDirection: TextDirection.rtl,
  child: Scaffold(body:ConvexAppBar(/*TODO ...*/)),
)

Custom Example

If the default style does not match with your situation, try with ConvexAppBar.builder(), which allow you to custom nearly all the tab features.

Scaffold(
  bottomNavigationBar: ConvexAppBar.builder(
    count: 5,
    backgroundColor: Colors.blue,
    style: TabStyle.fixed,
    itemBuilder: Builder(),
  )
);

// user defined class
class Builder extends DelegateBuilder {
  @override
  Widget build(BuildContext context, int index, bool active) {
    return Text('TAB $index');
  }
}

Download ConvexAppBar source code on GitHub

https://github.com/hacktons/convex_bottom_bar

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