这是因为您在导航到此页面时创建了TextEditingController，因此它将使用空文本创建。
因此，您可以使控制器全局化，而不是在StatefulWidget内部。

import 'package:flutter/material.dart';

class SearchScrean extends StatefulWidget {
  const SearchScrean({super.key});

  @override
  State<SearchScrean> createState() => _SearchScreanState();
}

class _SearchScreanState extends State<SearchScrean> {
  // you probably initialize the controller here or in initState.
  TextEditingController messageController = TextEditingController(); 
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Column(children: [
        TextFormField(
          controller: messageController,
          decoration: InputDecoration(
            border: InputBorder.none,
            hintText: "Message",
          ),
        ),
      ]),
    );
  }
}

看评论。
您必须像这样在外部初始化它，或者使用状态管理包，例如bloc或provider：

import 'package:flutter/material.dart';

// initialize it here or in another global file
TextEditingController messageController = TextEditingController(); 

class SearchScrean extends StatefulWidget {
  const SearchScrean({super.key});

  @override
  State<SearchScrean> createState() => _SearchScreanState();
}

class _SearchScreanState extends State<SearchScrean> {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Column(children: [
        TextFormField(
          controller: messageController,
          decoration: InputDecoration(
            border: InputBorder.none,
            hintText: "Message",
          ),
        ),
      ]),
    );
  }
}

当你不再需要它的时候就用messageController.dispose()处理掉它