update method Null safety

  1. @override
void update(
  1. covariant StatefulWidget newWidget
)
override

Change the widget used to configure this element.

The framework calls this function when the parent wishes to use a different widget to configure this element. The new widget is guaranteed to have the same runtimeType as the old widget.

This function is called only during the "active" lifecycle state.

Implementation

@override
void update(StatefulWidget newWidget) {
  super.update(newWidget);
  assert(widget == newWidget);
  final StatefulWidget oldWidget = state._widget!;
  // We mark ourselves as dirty before calling didUpdateWidget to
  // let authors call setState from within didUpdateWidget without triggering
  // asserts.
  _dirty = true;
  state._widget = widget as StatefulWidget;
  final Object? debugCheckForReturnedFuture = state.didUpdateWidget(oldWidget) as dynamic;
  assert(() {
    if (debugCheckForReturnedFuture is Future) {
      throw FlutterError.fromParts(<DiagnosticsNode>[
        ErrorSummary('${state.runtimeType}.didUpdateWidget() returned a Future.'),
        ErrorDescription( 'State.didUpdateWidget() must be a void method without an `async` keyword.'),
        ErrorHint(
          'Rather than awaiting on asynchronous work directly inside of didUpdateWidget, '
          'call a separate method to do this work without awaiting it.',
        ),
      ]);
    }
    return true;
  }());
  rebuild();
}