dynamic_stepper.dart

  // Replace _buildVertical() function of
  // flutter/packages/flutter/lib/src/material/stepper.dart

  Widget _buildVertical() {

    return ListView.builder(
      shrinkWrap: true,
      itemCount: widget.steps.length,
      itemBuilder: (BuildContext context, int i){

        i < _keys.length ? _keys[i] : _keys.add(GlobalKey());
        return Column(
          key: _keys[i],
          children: <Widget>[
            InkWell(
              onTap: widget.steps[i].state != StepState.disabled ? () {
                // In the vertical case we need to scroll to the newly tapped
                // step.
                Scrollable.ensureVisible(
                  _keys[i].currentContext,
                  curve: Curves.fastOutSlowIn,
                  duration: kThemeAnimationDuration,
                );

                if (widget.onStepTapped != null)
                  widget.onStepTapped(i);
              } : null,
              child: _buildVerticalHeader(i)
            ),
            _buildVerticalBody(i)
          ]
        );
      }
    );
  }