Customizing tabs alignment using the new TabBar.tabAlignment property

Using TabBar.tabAlignment to customize the alignment of tabs in a TabBar.

The TabBar.tabAlignment property sets where a Material 3 TabBar places tabs. The TabAlignment enum has the following values:

• TabAlignment.start: Aligns the tabs to the start of the scrollable TabBar.
• TabAlignment.startOffset: Aligns the tabs to the start of the scrollable TabBar with an offset of 52.0 pixels.
• TabAlignment.center: Aligns the tabs to the center of the TabBar.
• TabAlignment.fill: Aligns the tabs to the start and stretches the tabs to fill the fixed TabBar.

The scrollable TabBar supports the following alignments:

• TabAlignment.start
• TabAlignment.startOffset
• TabAlignment.center

The fixed TabBar supports the following alignments:

• TabAlignment.fill
• TabAlignment.center

When you set ThemeData.useMaterial3 to true, a scrollable TabBar aligns tabs as TabAlignment.startOffset by default. To change this alignment, set the TabBar.tabAlignment property for widget level customization. Or, set the TabBarThemeData.tabAlignment property for app level customization.

When you set TabBar.isScrollable and ThemeData.useMaterial3 to true, the tabs in a scrollable TabBar defaults to TabAlignment.startOffset. This aligns the tabs to the start of the scrollable TabBar with an offset of 52.0 pixels. This changes the previous behavior. The tabs were aligned to the start of the scrollable TabBar when more tabs needed to display than the width allowed.

A Material 3 scrollable TabBar uses TabAlignment.startOffset as the default tab alignment. This aligns the tabs to the start of the scrollable TabBar with an offset of 52.0 pixels.

To align the tabs to the start of the scrollable TabBar, set TabBar.tabAlignment to TabAlignment.start. This change also removed the 52.0 pixel offset. The following code snippets show how to use TabBar.tabAlignment to align tabs to the start of the scrollable TabBar:

Code before migration:

TabBar(
  isScrollable: true,
  tabs: List<Tab>.generate(
    count,
    (int index) => Tab(text: 'Tab $index'),
  ).toList(),
);

Code after migration:

TabBar(
  tabAlignment: TabAlignment.start,
  isScrollable: true,
  tabs: List<Tab>.generate(
    count,
    (int index) => Tab(text: 'Tab $index'),
  ).toList(),
);

Landed in version: 3.13.0-17.0.pre
In stable release: 3.16

API documentation:

• TabBar
• TabBar.tabAlignment
• TabAlignment

Relevant PRs:

• Introduce TabBar.tabAlignment
• Fix Material 3 Scrollable TabBar

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