constructor StatefulElement

Source

StatefulElement(StatefulWidget widget)
  : _state = widget.createState(), super(widget) {
  assert(() {
    if (!_state._debugTypesAreRight(widget)) {
      throw new FlutterError(
        'StatefulWidget.createState must return a subtype of State<${widget.runtimeType}>\n'
        'The createState function for ${widget.runtimeType} returned a state '
        'of type ${_state.runtimeType}, which is not a subtype of '
        'State<${widget.runtimeType}>, violating the contract for createState.'
      );
    }
    return true;
  });
  assert(_state._element == null);
  _state._element = this;
  assert(_builder == _buildNothing);
  _builder = _state.build;
  assert(_state._config == null);
  _state._config = widget;
  assert(_state._debugLifecycleState == _StateLifecycle.created);
}