Simple PageIndicator

app_page_indicator.dart

import 'package:flutter/material.dart';

class AppPageIndicator extends StatefulWidget {
  final PageController controller;
  final int numItems;
  final Color activeColor;
  final Color inactiveColor;
  final double dotSize;
  final bool fillDots;
  final EdgeInsets padding;
  final bool shadow;

  const AppPageIndicator(this.controller,
      {Key key,
      this.numItems = 0,
      this.activeColor,
      this.inactiveColor,
      this.dotSize = 8,
      this.fillDots = false,
      this.padding,
      this.shadow = true})
      : super(key: key);

  @override
  _AppPageIndicatorState createState() => _AppPageIndicatorState();
}

class _AppPageIndicatorState extends State<AppPageIndicator> {
  int _actualPage = 0;

  @override
  void initState() {
    super.initState();
    widget.controller.removeListener(_pageChange);
    widget.controller.addListener(_pageChange);
  }

  @override
  Widget build(BuildContext context) {
    return Container(
      padding: widget.padding,
      height: 8 + widget.dotSize,
      child: Row(
        mainAxisAlignment: MainAxisAlignment.center,
        children: _getDots(widget.numItems),
      ),
    );
  }

  _pageChange() {
    setState(() {
      _actualPage = widget.controller.page.round();
    });
  }

  Widget _dot(Color color, {double size = 8.0}) => Container(
        height: size,
        width: size,
        margin: EdgeInsets.all(4.0),
        decoration: ShapeDecoration(
            shape: CircleBorder(),
            color: color,
            shadows: widget.shadow
                ? [
                    BoxShadow(
                        color: Colors.black54,
                        offset: Offset(0, 1.5),
                        blurRadius: 1.5)
                  ]
                : []),
      );

  List<Widget> _getDots(int numItems) {
    var list = <Widget>[];
    for (var i = 0; i < numItems; i++) {
      list.add(_dot(
          (widget.fillDots ? i <= _actualPage : i == _actualPage)
              ? widget.activeColor
              : widget.inactiveColor,
          size: (widget.fillDots ? i <= _actualPage : i == _actualPage)
              ? widget.dotSize
              : widget.dotSize * 0.85));
    }
    return list;
  }
}