TabController constructor

TabController({
  1. int initialIndex = 0,
  2. Duration? animationDuration,
  3. required int length,
  4. required TickerProvider vsync,
})

Creates an object that manages the state required by TabBar and a TabBarView.

The length must not be negative. Typically it's a value greater than one, i.e. typically there are two or more tabs. The length must match TabBar.tabs's and TabBarView.children's length.

The initialIndex must be valid given length. If length is zero, then initialIndex must be 0 (the default).

Implementation

TabController({
  int initialIndex = 0,
  Duration? animationDuration,
  required this.length,
  required TickerProvider vsync,
}) : assert(length >= 0),
     assert(initialIndex >= 0 && (length == 0 || initialIndex < length)),
     _index = initialIndex,
     _previousIndex = initialIndex,
     _animationDuration = animationDuration ?? kTabScrollDuration,
     _animationController = AnimationController.unbounded(
       value: initialIndex.toDouble(),
       vsync: vsync,
     ) {
  if (kFlutterMemoryAllocationsEnabled) {
    ChangeNotifier.maybeDispatchObjectCreation(this);
  }
}