Flutter 实现简单搜索功能

先建立一个主文件，继承StatelessWidget,然后在home属性中加入SearchBarDemo，这是一个自定义的Widget，主要代码都在这个文件中。

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

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

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

然后是搜索页面，里面包含数据及搜索功能。

工作中这些数据是后台传递给我们，或者写成配置文件的，这里我们就以List的方式代替了。我们在这个文件中定义了两个List：

const searchList = [
  'jiejie-大长腿',
  'jiejie-水蛇腰',
  'gege-帅气欧巴',
  'gege-小鲜肉'
];

const recentSuggest = [
  '推荐-1',
  '推荐-2',
];

点击搜索按钮

class SearchBarDemo extends StatefulWidget {
  _SearchBarDemoState createState() => _SearchBarDemoState();
}

class _SearchBarDemoState extends State<SearchBarDemo> {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('SearchBarDemo'),
        actions: <Widget>[
          IconButton(
            icon: Icon(Icons.search),
            onPressed: (){
              showSearch(context: context,delegate: SearchBarDelegate());
            },
          )
        ],
        ),
      
    );
  }
}

在点击图标时执行SearchBarDelegate 类，这个类继承与SearchDelegate类，继承后要重写里边的四个方法。

重写buildActions方法：

buildActions方法时搜索条右侧的按钮执行方法，我们在这里方法里放入一个clear图标。 当点击图片时，清空搜索的内容。

buildLeading 方法重写

这个时搜索栏左侧的图标和功能的编写，这里我们才用AnimatedIcon，然后在点击时关闭整个搜索页面。

buildResults方法重写

buildResults方法，是搜到到内容后的展现，因为我们的数据都是模拟的，所以我这里就使用最简单的Container+Card组件进行演示了。

buildSuggestions方法重写

这个方法主要的作用就是设置推荐，就是我们输入一个字，然后自动为我们推送相关的搜索结果。

class SearchBarDelegate extends SearchDelegate<String>{
  //清空按钮
  @override
  List<Widget>buildActions(BuildContext context){
    return [
      IconButton(
        icon: Icon(Icons.clear),
        onPressed: () => query = "", //搜索值为空
      )
    ]; 
  }
  //返回上级按钮
  @override
  Widget buildLeading(BuildContext context) {
    return IconButton(
      icon: AnimatedIcon(
        icon: AnimatedIcons.menu_arrow, progress: transitionAnimation
      ),
      onPressed: () => close(context, null)  //点击时关闭整个搜索页面
    );
  }
  //搜到到内容后的展现
  @override
  Widget buildResults(BuildContext context){
    return Container(
       100.0,
      height:100.0,
      child: Card(
        color:Colors.redAccent,
        child: Center(
          child: Text(query),
        ),
      ),
    );
  }
  //设置推荐
  @override
  Widget buildSuggestions(BuildContext context){
    final suggestionsList= query.isEmpty
      ? recentSuggest 
      : searchList.where((input)=> input.startsWith(query)).toList();

    return ListView.builder(
      itemCount:suggestionsList.length,
      itemBuilder: (context,index) => ListTile(
        title: RichText( //富文本
          text: TextSpan(
            text: suggestionsList[index].substring(0,query.length),
            style: TextStyle(color: Colors.black,fontWeight: FontWeight.bold),
            children: [
              TextSpan(
                text: suggestionsList[index].substring(query.length),
                style: TextStyle(color: Colors.grey)
              )
            ]
          ),
        ),
      ),
    );  
  }

}

完整的search_bar_demo.dart文件代码如下：

import 'package:flutter/material.dart';

const searchList = [
  'jiejie-大长腿',
  'jiejie-水蛇腰',
  'gege-帅气欧巴',
  'gege-小鲜肉'
];

const recentSuggest = [
  '推荐-1',
  '推荐-2',
];

class SearchBarDemo extends StatefulWidget {
 
  _SearchBarDemoState createState() => _SearchBarDemoState();
}

class _SearchBarDemoState extends State<SearchBarDemo> {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('SearchBarDemo'),
        actions: <Widget>[
          IconButton(
            icon: Icon(Icons.search),
            onPressed: (){
              showSearch(context: context,delegate: SearchBarDelegate());
            },
          )
        ],
        ),
      
    );
  }
}

class SearchBarDelegate extends SearchDelegate<String>{
  //清空按钮
  @override
  List<Widget>buildActions(BuildContext context){
    return [
      IconButton(
        icon: Icon(Icons.clear),
        onPressed: () => query = "", //搜索值为空
      )
    ]; 
  }
  //返回上级按钮
  @override
  Widget buildLeading(BuildContext context) {
    return IconButton(
      icon: AnimatedIcon(
        icon: AnimatedIcons.menu_arrow, progress: transitionAnimation
      ),
      onPressed: () => close(context, null)  //点击时关闭整个搜索页面
    );
  }
  //搜到到内容后的展现
  @override
  Widget buildResults(BuildContext context){
    return Container(
       100.0,
      height:100.0,
      child: Card(
        color:Colors.redAccent,
        child: Center(
          child: Text(query),
        ),
      ),
    );
  }
  //设置推荐
  @override
  Widget buildSuggestions(BuildContext context){
    final suggestionsList= query.isEmpty
      ? recentSuggest 
      : searchList.where((input)=> input.startsWith(query)).toList();

    return ListView.builder(
      itemCount:suggestionsList.length,
      itemBuilder: (context,index) => ListTile(
        title: RichText( //富文本
          text: TextSpan(
            text: suggestionsList[index].substring(0,query.length),
            style: TextStyle(color: Colors.black,fontWeight: FontWeight.bold),
            children: [
              TextSpan(
                text: suggestionsList[index].substring(query.length),
                style: TextStyle(color: Colors.grey)
              )
            ]
          ),
        ),
      ),
    );  
  }

}