listview - 从 ListView 中 flutter 删除项目

Question

我试过了

Write Your First Flutter App, part 2 flutter app page 5

我现在对此应用程序有疑问。我想从该 List onLongPress 中删除一个条目，如下所示:

 onLongPress: () {
              setState(() {
                _saved.remove(pair);
              });
            },

这将从列表中删除该项目，但不会更新屏幕。返回家中并重新打开此路线后，新项目没有被删除。但是如何在没有用户重新打开页面的情况下触发此页面上的更新。

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

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return new MaterialApp(
      title: 'Startup Name Generator',
      home: RandomWords(),
      theme: new ThemeData(
        primaryColor: Colors.orange,
      ),
    );
  }
}

class RandomWords extends StatefulWidget {
  @override
  RandomWordsState createState() => RandomWordsState();
}

class RandomWordsState extends State<RandomWords> {
  final List<WordPair> _suggestions = <WordPair>[];
  final TextStyle _biggerFont = const TextStyle(fontSize: 18);
  final Set<WordPair> _saved = new Set<WordPair>();

  _buildSuggestions() {
    return ListView.builder(
      padding: const EdgeInsets.all(16),
      itemBuilder: (context, i) {
        if (i.isOdd) return Divider();

        final index = i ~/ 2;
        if (index >= _suggestions.length) {
          _suggestions.addAll(generateWordPairs().take(10));
        }
        return _buildRow(_suggestions[index]);
      },
    );
  }

  Widget _buildRow(WordPair pair) {
    final bool alreadySaved = _saved.contains(pair);

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

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text("Startup Name Generator"),
        actions: <Widget>[
          new IconButton(icon: const Icon(Icons.list), onPressed: _pushSaved),
        ],
      ),
      body: _buildSuggestions(),
    );
  }

  void _pushSaved() {
    Navigator.of(context).push(
      new MaterialPageRoute(
        builder: (BuildContext context) {
          final Iterable<ListTile> tiles = _saved.map(
            (WordPair pair) {
              return new ListTile(
//this is the delete operation
                onLongPress: () {
                  setState(() {
                    _saved.remove(pair);
                  });
                },
                title: new Text(
                  pair.asPascalCase,
                  style: _biggerFont,
                ),
              );
            },
          );

          final List<Widget> divided = ListTile.divideTiles(
            context: context,
            tiles: tiles,
          ).toList();

          return new Scaffold(
            appBar: new AppBar(
              title: const Text('Saved Suggestions'),
            ),
            body: new ListView(children: divided),
          );
        },
      ),
    );
  }
}

Answer 1

2019-11月最新方式

更多信息https://www.youtube.com/watch?v=iEMgjrfuc58

                 ListView.builder/GridView.builder(
                   itemBuilder: (BuildContext context, int index){
                      return Dismissible(
                      key: Key(selectServiceLocations[index].toString()),
                      onDismissed: (direction) {
                        setState(() {
                         selectServiceLocations.removeAt(index);
                        });
                      },
                     child: Container(...)
}
)