flutter中获取子组件Widget调用方法及访问属性

flutter可以通过key来实现。每个Widget都是唯一标识的。此唯一标识对应于可选的Key参数。如果省略，Flutter将为您生成一个。key主要分为四种：GlobalKey，LocalKey，UniqueKey或ObjectKey.

示例

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

class StartDemo extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    // 定义一个全局key
    GlobalKey<_RandomWordsStateState> _childKey =
        new GlobalKey<_RandomWordsStateState>();

    void _pushSaved() {
      // 调用子组件方法
      _childKey.currentState.hello();

      Navigator.of(context).push(MaterialPageRoute(builder: (context) {
        final titles = _childKey.currentState.saved.map((pair) {
          return ListTile(
            title: Text(
              pair.asString,
              style: TextStyle(fontSize: 18.0),
            ),
          );
        });
        final divided =
            ListTile.divideTiles(tiles: titles, context: context).toList();
        return Scaffold(
          appBar: AppBar(
            title: Text('Saved Suggestions'),
          ),
          body: ListView(
            children: divided,
          ),
        );
      }));
    }

    return Scaffold(
      appBar: AppBar(
        title: Text('welcome to flutter'),
        actions: <Widget>[
          IconButton(
            icon: Icon(Icons.list),
            onPressed: _pushSaved,
          )
        ],
      ),
      body: RandomWordsState(key: _childKey),
    );
  }
}

class RandomWordsState extends StatefulWidget {
  RandomWordsState({Key key}) : super(key: key);

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

class _RandomWordsStateState extends State<RandomWordsState> {
  @override
  Widget build(BuildContext context) {
    return _buildSuggestions();
  }

  void hello() {
    print('hello flutter.');
  }

  // 下划线开头是私有变量
  final _suggestions = <WordPair>[];

  final saved = new Set<WordPair>();

  Widget _buildSuggestions() {
    return ListView.builder(
      itemBuilder: (context, i) {
        // 分割线
        if (i.isOdd) {
          return Divider();
        }
        final index = i ~/ 2;
        if (index >= _suggestions.length) {
          _suggestions.addAll(generateWordPairs().take(10));
        }
        return _buildRow(_suggestions[index]);
      },
    );
  }

  final _biggerFont = const TextStyle(fontSize: 18.0);

  Widget _buildRow(WordPair pair) {
    // 是否已收藏
    final alreadySaved = saved.contains(pair);

    return ListTile(
      title: Text(
        pair.asLowerCase,
        style: _biggerFont,
      ),
      trailing: Icon(alreadySaved ? Icons.favorite : Icons.favorite_border,
          color: alreadySaved ? Colors.red : null),
      onTap: () {
        setState(() {
          if (alreadySaved) {
            saved.remove(pair);
          } else {
            saved.add(pair);
          }
        });
      },
    );
  }
}

参考文献

https://www.jianshu.com/p/b16f70dd692c

赏

谢谢你请我吃糖果

支付宝

微信