getInitialState method

@override Map getInitialState()

Invoked once before the Component is mounted. The return value will be used as the initial value of state.

See: reactjs.org/docs/react-component.html#getinitialstate

Implementation

@override
Map getInitialState() => (newState()
  ..transitionPhase = this.initiallyShown ? TransitionPhase.SHOWN : TransitionPhase.HIDDEN
);