/// 自定义PageView分页指示器
library;

import 'package:flutter/material.dart';

class CustomPageViewIndicator extends StatefulWidget {
  const CustomPageViewIndicator({
    super.key,
    required this.count,
    required this.controller,
    this.color = Colors.black12,
    this.activeColor = Colors.black26,
    this.pageSnapping = true,
  });

  /// 数量
  final int count;
  final PageController controller;
  /// 颜色
  final Color color;
  /// 激活颜色
  final Color activeColor;
  // 是否停止滑动时吸附到最近页面
  final bool pageSnapping;

  @override
  State<CustomPageViewIndicator> createState() => _CustomPageViewIndicatorState();
}

class _CustomPageViewIndicatorState extends State<CustomPageViewIndicator> {
  int pageIndex = 0;
  double page = 0;

  // 圆点指示器
  Widget dotIndicator() {
    return Row(
      mainAxisAlignment: MainAxisAlignment.center,
      children: List.generate(
        widget.count,
        (index) => Container(
          margin: EdgeInsets.symmetric(horizontal: 3.0),
          width: pageIndex == index ? 15.0 : 4.0,
          height: 4.0,
          decoration: BoxDecoration(
            borderRadius: BorderRadius.circular(10.0),
            color: pageIndex == index ? widget.activeColor : widget.color,
          ),
        ),
      ),
    );
  }
  // 滚动槽指示器
  Widget scrollIndicator() {
    return Stack(
      children: [
        Container(
          decoration: BoxDecoration(
            color: widget.color,
            borderRadius: BorderRadius.circular(50.0),
          ),
          height: 4.0,
          width: (widget.count - 1) * 15.0 + 15.0,
        ),
        Container(
          margin: EdgeInsets.only(left: page * 15.0),
          decoration: BoxDecoration(
            color: widget.activeColor,
            borderRadius: BorderRadius.circular(50.0),
          ),
          width: 15.0,
          height: 4.0,
        ),
      ],
    );
  }

  @override
  Widget build(BuildContext context) {
    return widget.count > 1 ?
      widget.pageSnapping ? dotIndicator() : scrollIndicator()
      :
      SizedBox.shrink();
  }

  void _setInitialPage() {
    pageIndex = widget.controller.initialPage;
    page = pageIndex.toDouble();
  }

  void _onController() {
    if (!widget.controller.hasClients) return;
    page = widget.controller.page ?? 0.0;
    pageIndex = page.round();
    setState(() {});
  }

  @override
  void initState() {
    super.initState();
    widget.controller.addListener(_onController);
    _setInitialPage();
  }

  @override
  void didUpdateWidget(CustomPageViewIndicator oldWidget) {
    super.didUpdateWidget(oldWidget);
    if (widget.controller != oldWidget.controller) {
      oldWidget.controller.removeListener(_onController);
      widget.controller.addListener(_onController);
    }
  }

  @override
  void dispose() {
    widget.controller.removeListener(_onController);
    super.dispose();
  }
}