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A Flutter package which implements a ConvexAppBar to show a convex tab in the bottom bar. Theming supported.

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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

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 Pub:

  convex_bottom_bar: ^latest_version
import 'package:convex_bottom_bar/convex_bottom_bar.dart';

  bottomNavigationBar: ConvexAppBar(
    items: [
      TabItem(icon: Icons.home, title: 'Home'),
      TabItem(icon:, 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.

Stable Flutter Version Package Version More
>=1.20 >=2.4.0 Since v1.20, the stable version changed the Stack api
<1.20 <=2.3.0 Support for stable version such as v1.17, v1.12 is not going to be updated

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 #

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

Attributes Description
backgroundColor AppBar background
gradient gradient will override backgroundColor
height AppBar height
color tab icon/text color
activeColor tab icon/text color when selected
curveSize size of the convex shape
top top edge of the convex shape relative to AppBar
cornerRadius draw the background with topLeft and topRight corner; Only work with fixed tab style
style style to describe the convex shape: fixed, fixedCircle, react, reactCircle, ...
chipBuilder custom badge builder, use ConvexAppBar.badge for default badge

Badge #

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

badge demo

ConvexAppBar.badge({0: '99+', 1: Icons.assistant_photo, 2: Colors.redAccent},
  items: [
    TabItem(icon: Icons.home, title: 'Home'),
    TabItem(icon:, 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.


  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.

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

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

  double get activeIconMargin => 10;

  double get iconSize => 20;

  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:

  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.

  bottomNavigationBar: ConvexAppBar.builder(
    count: 5,
    style: TabStyle.fixed,
    itemBuilder: Builder(),

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

Full custom example can be found at example.


Please file feature requests and bugs at the issue tracker.

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A Flutter package which implements a ConvexAppBar to show a convex tab in the bottom bar. Theming supported.

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