搜素下拉框提示.gif

main

import 'package:flutter/material.dart';
import 'search_bar_demo.dart';
main(){
  runApp(MyApp());
}
class MyApp extends StatelessWidget {

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData.light(),
      home: SearchBarDemo(),

    );
  }
}

search_bar_demo

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'),
        // 使用搜索那个放大镜图标
        actions: <Widget>[
          IconButton(
            icon: Icon(Icons.search),
            onPressed: (){
              // 调用写好的方法
            showSearch(context: context,delegate: SearchBar());
            },
          )
        ],
      ),
    );
  }
}


class SearchBar extends SearchDelegate<String>{

  // 点击清楚的方法
  @override
  List<Widget> buildActions(BuildContext context) {
    return [
      IconButton(
        icon: Icon(Icons.clear),
        // 点击把文本空的内容清空
        onPressed: (){
          query = "";
        },
      )
    ];
  }

  // 点击箭头返回
  @override
  Widget buildLeading(BuildContext context) {
    return IconButton(
      icon: AnimatedIcon(
                                          // 使用动画效果返回
        icon: AnimatedIcons.menu_arrow,progress: transitionAnimation,
      ),
      // 点击的时候关闭页面（上下文）
      onPressed: (){
        close(context, null);
      },
    );
  }

  // 点击搜索出现结果
  @override
  Widget buildResults(BuildContext context) {
    return Container(
      width: 100,
      height: 100,
      child: Card(
        color: Colors.pink,
        child: Center(
          child: Text(query),
        ),
      ),
    );
  }

  // 搜索下拉框提示的方法
  @override
  Widget buildSuggestions(BuildContext context) {
    // 定义变量 并进行判断
    final suggestionList = query.isEmpty
    ? recentSuggest
    :searchList.where((input) => input.startsWith(query)).toList();
    return ListView.builder(
      itemCount: suggestionList.length, 
      itemBuilder: (context,index){
        return  ListTile(
        title: RichText(
                  text: TextSpan(
                    // 获取搜索框内输入的字符串，设置它的颜色并让让加粗
                      text: suggestionList[index].substring(0, query.length),
                      style: TextStyle(
                          color: Colors.black, fontWeight: FontWeight.bold),
                      children: [
                    TextSpan(
                      //获取剩下的字符串，并让它变成灰色
                        text: suggestionList[index].substring(query.length),
                        style: TextStyle(color: Colors.grey))
                  ]
                  )
                  )
                  );
      }
    );
  }
}

模拟的假数据asset

// 模拟的假数据
const searchList = [
  "lao-老王",
  "lao-老张",
  "xiao-小王",
  "xiao-小张"
];

const recentSuggest = [
  "马云-1",
  "马化腾-2"
];