<> Main entry file 
 inherit StatelessWidget, And then in the home Attribute SearchBarDemo, This is a custom one Widget, The main code is in this file .
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() ); } } 
 <> data file  asset.dart
asset.dart Equivalent to data file , At work, these data are transmitted to us in the background , Or write it as a configuration file , Here we will take List Instead . We define two in this document List:
 * 
searchList :  This is equivalent to the data in the database , We're going to search here .
 * 
recentSuggest :  Current recommended data , When searching , Automatically recommend for us .
const searchList = [ "jiejie- long legs ", "jiejie- Water snake waist ", "gege1- Handsome Europa ", "gege2- little fresh meat " ]; 
const recentSuggest = [ " recommend -1", " recommend -2" ]; 
 <>AppBar Style making 
import 'package:flutter/material.dart'; import 'asset.dart'; 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: (){ print(' Start searching '); } ), ] ) ); } } 
 <> rewrite buildActions method :
buildActions Method, the button to the right of the search bar executes the method , We put one in the method here clear Icon .  When clicking on an image , Empty search content .
 @override List<Widget> buildActions(BuildContext context){ return [ 
IconButton( icon:Icon(Icons.clear), onPressed: ()=>query = "",) ]; } 
 <>buildLeading  Method rewriting 
 The left side of the search bar icon and function of the writing 
 @override Widget buildLeading(BuildContext context) { return IconButton( 
icon: AnimatedIcon( icon: AnimatedIcons.menu_arrow, progress: 
transitionAnimation), onPressed: () => close(context, null)); } 
 <>buildResults Method rewriting 
buildResults method , It's the display after finding the content ,
@override Widget buildResults(BuildContext context) { return Container( width: 
100.0, height: 100.0, child: Card( color: Colors.redAccent, child: Center( 
child: Text(query), ), ), ); } 
 <>buildSuggestions Method rewriting 
 The main function of this method is to set recommendations , That is, we type in a word , Then automatically push relevant search results for us 
@override Widget buildSuggestions(BuildContext context) { final suggestionList 
= query.isEmpty ? recentSuggest : searchList.where((input) => 
input.startsWith(query)).toList(); return ListView.builder( itemCount: 
suggestionList.length, itemBuilder: (context, index) => ListTile( title: 
RichText( text: TextSpan( text: suggestionList[index].substring(0, 
query.length), style: TextStyle( color: Colors.black, fontWeight: 
FontWeight.bold), children: [ TextSpan( text: 
suggestionList[index].substring(query.length), style: TextStyle(color: 
Colors.grey)) ])), )); } } 
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