flutter 组件——展示更多

笔者自己封装的一个flutter组件，用于展示网格数据。可以传入默认展示的数目，网格的列数，展开和收起时显示的文字等。需注意的是，该组件需要传入一个itemBuilder函数，这个函数有context和index两个参数，即网格的子项构造函数。还需要传入一个包含所有网格数据的数组。网格的子项宽高比childAspectRatio也是可以传入的。

import 'package:flutter/material.dart';

class MoreData extends StatefulWidget {
  final List list;
  final int firstShowCount;
  final int crossCount;
  final double childAspectRatio;
  final IndexedWidgetBuilder itemBuilder;
  final String expandedText;
  final String tightText;

  const MoreData({
    Key? key,
    required this.list,
    required this.firstShowCount,
    required this.itemBuilder,
    this.childAspectRatio = 2.5,
    this.crossCount = 4,
    this.expandedText = '收起',
    this.tightText = '查看更多',
  }) : super(key: key);

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

class _MoreDataState extends State {
  int currentListLength = 0;
  bool isExpanded = false;

  @override
  void initState() {
    super.initState();
    currentListLength = widget.list.length > widget.firstShowCount
        ? widget.firstShowCount
        : widget.list.length;
  }

  @override
  Widget build(BuildContext context) {
    return getMoreData();
  }

  Widget getMoreData() {
    if (widget.list.length > widget.firstShowCount) {
      return Column(
        children: [
          getList(),
          getButton(),
        ],
      );
    }

    return getList();
  }

  Widget getList() {
    return GridView.builder(
      physics: const NeverScrollableScrollPhysics(),
      shrinkWrap: true,
      itemCount: currentListLength,
      itemBuilder: widget.itemBuilder,
      gridDelegate: SliverGridDelegateWithFixedCrossAxisCount(
        childAspectRatio: widget.childAspectRatio,
        crossAxisCount: widget.crossCount,
        mainAxisSpacing: 5,
        crossAxisSpacing: 5,
      ),
    );
  }

  Widget getButton() {
    return GestureDetector(
      onTap: () {
        if (isExpanded) {
          setState(() {
            currentListLength = widget.firstShowCount;
          });
        } else {
          setState(() {
            currentListLength = widget.list.length;
          });
        }

        setState(() {
          isExpanded = !isExpanded;
        });
      },
      child: Container(
        height: 23,
        margin: const EdgeInsets.only(right: 15, bottom: 20),
        decoration: BoxDecoration(
          borderRadius: BorderRadius.circular(4),
          color: const Color(0xfffefefe),
        ),
        alignment: Alignment.center,
        child: Row(
          mainAxisSize: MainAxisSize.min,
          children: [
            Text(
              isExpanded ? widget.expandedText : widget.tightText,
              style: const TextStyle(
                fontSize: 11,
                color: Color(0xff999999),
              ),
            ),
            const SizedBox(width: 6),
            Icon(
              isExpanded ? Icons.keyboard_arrow_up : Icons.keyboard_arrow_down,
              size: 11,
              color: const Color(0xff999999),
            ),
          ],
        ),
      ),
    );
  }
}