flutter_swiper自定义分页指示器

flutter_swiper内置了2种分页指示器，一种是SwiperPagination.dots的圆形风格，一种是SwiperPagination.fraction的数字风格，但是这显然不能满足我们的需要，比如下图这种效果：

flutter_swiper提供了这样的能力，但是需要你自己实现

 

你可以看到这文档简直简单，就一个方法就没了，让人摸不到头脑。不慌，你可以看SwiperPagination.dots的实现，就发现其实就一个StatefulWidget，参考源码后，我的代码如下：

新建一个custom_swiper_pagination.dart（flutter2.x+card_swiper 此库是flutter_swiper的空安全版）

import 'dart:developer';
import 'package:flutter/material.dart';
import 'package:card_swiper/card_swiper.dart';

/// 自定义页面指示器
class CustomSwiperPaginationBuilder extends SwiperPlugin {
  // 当滚动到此时的颜色
  late Color? activeColor;

  // 默认颜色
  late Color? color;

  // 每个圆点的间距
  final double space;

  // 每个圆点的大小
  final double size;

  // 特殊点的宽度
  final double activeSize;

  final double bottom;

  final AlignmentGeometry? alignment;

  final Key? key;

  CustomSwiperPaginationBuilder(
      {this.color = Colors.grey,
      this.activeColor = Colors.blue,
      this.space = 3.0,
      this.size = 6.0,
      this.activeSize = 20.0,
      this.bottom = 0.0,
      this.alignment = Alignment.center,
      this.key});

  @override
  Widget build(BuildContext context, SwiperPluginConfig config) {
    // 处理边界情况
    if (config.itemCount > 20) {
      log(
        'The itemCount is too big, we suggest use FractionPaginationBuilder '
        'instead of DotSwiperPaginationBuilder in this situation',
      );
    }

    int activeIndex = config.activeIndex;
    // 用于存放小圆点
    List list = [];
    for (var i = 0; i < config.itemCount; ++i) {
      if (activeIndex == i) {
        list.add(Container(
            key: Key('pagination_$i'),
            margin: EdgeInsets.all(space),
            child: PhysicalModel(
              color: Colors.transparent,
              borderRadius: BorderRadius.circular(10),
              clipBehavior: Clip.antiAlias,
              child: Container(
                color: activeColor,
                width: activeSize,
                height: size,
              ),
            )));
      } else {
        list.add(Container(
          key: Key('pagination_$i'),
          margin: EdgeInsets.all(space),
          child: ClipOval(
            // 圆角组件
            child: Container(
              color: color,
              width: size,
              height: size,
            ),
          ),
        ));
      }
    }

    return Stack(
      clipBehavior: Clip.none,
      children: [
        Positioned(
            left: 15,
            right: 15,
            bottom: bottom,
            child: Container(
              alignment: alignment,
              color: Colors.transparent,
              child: Row(
                key: key,
                mainAxisSize: MainAxisSize.min,
                mainAxisAlignment: MainAxisAlignment.center,
                children: list,
              ),
            ))
      ],
    );
  }
}

使用此方法：

child: Swiper(
          itemBuilder: (BuildContext context, int index) {
            var swiperItem = swiperList[index];
            return PhysicalModel(
              color: Colors.transparent,
              borderRadius: BorderRadius.circular(10),
              clipBehavior: Clip.antiAlias,
              child: Image.network(
                swiperItem?.img ?? '',
                fit: BoxFit.cover,
              ),
            );
          },
          viewportFraction: 0.85,
          scale: 0.9,
          autoplay: swiperList.isNotEmpty,
          itemCount: swiperList.length,
          pagination: SwiperPagination( // 此处使用自己编写的样式
            builder: CustomSwiperPaginationBuilder(alignment: Alignment.bottomCenter),
          ),
          // control: const SwiperControl(),
        ),

flutter_swiper默认是在图片内部的，因为我需要它显示在外面，因此使用了Stack组件。

注意：autoplay: swiperList.isNotEmpty最好使用isNotEmpty而不是true，否则就可能出现下面这种情况：

 

最终效果: