Flutter SearchDelegate 的使用案例

import 'package:flutter/material.dart';

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      home: MyHomePage(),
    );
  }
}

class MyHomePage extends StatefulWidget {
  @override
  _MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  final _searchDelegate = MySearchDelegate();

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('My App'),
        actions: [
          IconButton(
            icon: Icon(Icons.search),
            onPressed: () {
              showSearch(context: context, delegate: _searchDelegate);
            },
          ),
        ],
      ),
      body: Center(
        child: Text('Home Page'),
      ),
    );
  }
}

class MySearchDelegate extends SearchDelegate {
  @override
  List<Widget> buildActions(BuildContext context) {
    return [
      IconButton(
        icon: Icon(Icons.clear),
        onPressed: () {
          query = '';
        },
      ),
    ];
  }

  @override
  Widget buildLeading(BuildContext context) {
    return IconButton(
      icon: Icon(Icons.arrow_back),
      onPressed: () {
        close(context, null);
      },
    );
  }

  @override
  Widget buildResults(BuildContext context) {
    return Center(
      child: Text(query),
    );
  }

  @override
  Widget buildSuggestions(BuildContext context) {
    final suggestions = query.isEmpty
        ? ['apple', 'banana', 'orange']
        : ['apple', 'banana', 'orange']
            .where((s) => s.startsWith(query))
            .toList();

    return ListView.builder(
      itemCount: suggestions.length,
      itemBuilder: (context, index) {
        return ListTile(
          title: Text(suggestions[index]),
        );
      },
    );
  }
}