lift-app/lib/widgets/smooth_star_rating.dart

import 'package:flutter/material.dart';

typedef void RatingChangeCallback(double rating);

class SmoothStarRating extends StatelessWidget {
  final int starCount;
  final double rating;
  final RatingChangeCallback onRatingChanged;
  final Color color;
  final Color borderColor;
  final double size;
  final bool allowHalfRating;
  Widget iconNormal;
  Widget iconSelected;

  SmoothStarRating(
      {this.starCount = 5,
        this.rating = 0.0,
        this.onRatingChanged,
        this.color,
        this.borderColor,
        this.size,
        this.allowHalfRating = true,
        this.iconNormal,
        this.iconSelected}) {
    assert(this.rating != null);
  }

  Widget buildStar(BuildContext context, int index) {
    Widget iconWidget;
    if (index >= rating) {
//      icon = new Icon(
//        Icons.star_border,
//        color: borderColor ?? Theme.of(context).primaryColor,
//        size: size ?? 25.0,
//      );
      iconWidget = iconNormal;
    } else if (index > rating - (allowHalfRating ? 0.5 : 1.0) &&
        index < rating) {
//      icon = new Icon(
//        Icons.star_half,
//        color: color ?? Theme.of(context).primaryColor,
//        size: size ?? 25.0,
//      );
    } else {
//      icon = new Icon(
//        Icons.star,
//        color: color ?? Theme.of(context).primaryColor,
//        size: size ?? 25.0,
//      );
      iconWidget = iconSelected;
    }

    return new GestureDetector(
      onTap: () {
        if (this.onRatingChanged != null) onRatingChanged(index + 1.0);
      },
      onHorizontalDragUpdate: (dragDetails) {
        RenderBox box = context.findRenderObject();
        var _pos = box.globalToLocal(dragDetails.globalPosition);
        var i = _pos.dx / size;
        var newRating = allowHalfRating ? i : i.round().toDouble();
        if (newRating > starCount) {
          newRating = starCount.toDouble();
        }
        if (newRating < 0) {
          newRating = 0.0;
        }
        if (this.onRatingChanged != null) onRatingChanged(newRating);
      },
      child:Container(
        padding: EdgeInsets.only(left: 5,right: 5),
        child: iconWidget,
      ),
    );
  }

  @override
  Widget build(BuildContext context) {
    return new Material(
      color: Colors.transparent,
      child: new Wrap(
          alignment: WrapAlignment.start,
          children: new List.generate(
              starCount, (index) => buildStar(context, index))),
    );
  }
}