AnimatedList 列表动画

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

void main() {
  runApp(MyApp());
}

class MyApp extends StatefulWidget {
  const MyApp({Key? key}) : super(key: key);
  State<MyApp> createState() => _MyApp();
}

class _MyApp extends State<MyApp> {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        body: AnimatedListRoute(),
      ),
    );
  }
}

class AnimatedListRoute extends StatefulWidget {
  const AnimatedListRoute({Key? key}) : super(key: key);

  @override
  State<AnimatedListRoute> createState() => _AnimatedListRouteState();
}

class _AnimatedListRouteState extends State<AnimatedListRoute> {
  var data = <String>[];
  int counter = 15;

  final globalKey = GlobalKey<AnimatedListState>();

  @override
  void initState() {
    for (var i = 0; i < counter; i++) {
      data.add('${i + 1}');
    }
    super.initState();
  }

  Widget _buildItem(
    String item,
    int index,
    Animation<double> animation,
  ) {
    String char = data[index];
    return SlideTransition(
      position: Tween<Offset>(
        begin: Offset(0.0, 1.0), // 起始位置：向右偏移一个子部件的宽度
        end: Offset(0.0, 0.0), // 结束位置：回到正常位置
      ).animate(animation),
      child: ListTile(
        //数字不会重复，所以作为Key
        key: ValueKey(char),
        title: Text(char),
        trailing: IconButton(
          icon: Icon(Icons.delete),
          // 点击时删除
          onPressed: () => onDelete(context, index),
        ),
      ),
    );
  }

  @override
  Widget build(BuildContext context) {
    return Stack(
      children: [
        AnimatedList(
          key: globalKey,
          initialItemCount: data.length,
          itemBuilder: (
            BuildContext context,
            int index,
            Animation<double> animation,
          ) {
            //添加列表项时会执行渐显动画
            return _buildItem(data[index], index, animation);
          },
        ),
        buildAddBtn(),
      ],
    );
  }

  // 创建一个 “+” 按钮，点击后会向列表中插入一项
  Widget buildAddBtn() {
    return Positioned(
      child: FloatingActionButton(
        child: Icon(Icons.add),
        onPressed: () {
          // 添加一个列表项
          data.add('${++counter}');
          // 告诉列表项有新添加的列表项
          globalKey.currentState!.insertItem(data.length - 1);
          print('添加 $counter');
        },
      ),
      bottom: 30,
      left: 0,
      right: 0,
    );
  }

  // 构建列表项
  Widget buildItem(context, index) {
    String char = data[index];
    return ListTile(
      //数字不会重复，所以作为Key
      key: ValueKey(char),
      title: Text(char),
      trailing: IconButton(
        icon: Icon(Icons.delete),
        // 点击时删除
        onPressed: () => onDelete(context, index),
      ),
    );
  }

  void onDelete(context, index) {
    // 待实现
    setState(() {
      globalKey.currentState!.removeItem(
        index,
        (context, animation) {
          // 删除过程执行的是反向动画，animation.value 会从1变为0
          var item = buildItem(context, index);
          print('删除 ${data[index]}');
          data.removeAt(index);
          // 删除动画是一个合成动画：渐隐 + 收缩列表项
          return FadeTransition(
            opacity: CurvedAnimation(
              parent: animation,
              //让透明度变化的更快一些
              curve: const Interval(0.5, 1.0),
            ),
            // 不断缩小列表项的高度
            child: SizeTransition(
              sizeFactor: animation,
              axisAlignment: 0.0,
              child: item,
            ),
          );
        },
        duration: Duration(milliseconds: 200), // 动画时间为 200 ms
      );
    });
  }
}
AnimatedList 列表动画 ​

AnimatedList 列表动画
