如果你正在使用TextEditingController，然后设置文本为它，如下所示

TextEditingController _controller = new TextEditingController();


_controller.text = 'your initial text';

final your_text_name = TextFormField(
      autofocus: false,
      controller: _controller,
      decoration: InputDecoration(
        hintText: 'Hint Value',
      ),
    );

如果你不使用任何TextEditingController，那么你可以直接使用initialValue如下

final last_name = TextFormField(
      autofocus: false,
      initialValue: 'your initial text',
      decoration: InputDecoration(
        hintText: 'Last Name',
      ),
    );

更多参考TextEditingController

class _YourClassState extends State<YourClass> {
  TextEditingController _controller = TextEditingController();

  @override
  void initState() {
    super.initState();
    _controller.text = 'Your message';
  }

  @override
  Widget build(BuildContext context) {
    return Container(
      color: Colors.white,
      child: TextFormField(
        controller: _controller,
        decoration: InputDecoration(labelText: 'Send message...'),
      ),
    );
  }
}

由于没有一个答案提到它，TextEditingController应该在使用后被丢弃。如:

class MyWidget extends StatefulWidget {
  const MyWidget({Key? key}) : super(key: key);

  @override
  MyWidgetState createState() => MyWidgetState();
}

class MyWidgetState extends State<MyWidget> {
  final myController = TextEditingController(text: "Initial value");

  @override
  Widget build(BuildContext context) {
    return TextField(
      controller: myController,
    );
  }

  @override
  void dispose() {
    // dispose it here
    myController.dispose();
    super.dispose();
  }
}

当你使用TextEditingController

如果使用TextEditingController，请将其文本字段设置为所需的值

TextEditingController txtController = TextEditingController()..text = 'Your initial text value'; 
TextField( controller: txtController ..... ) 

当你不使用TextEditingController

如果你没有使用texteditingcontroller，直接从TextField小部件使用initialValue字段:

TextFormField( initialValue: "Your initial text value" )

如果您使用文本表单字段并将数据从上一页传递到下一页文本表单字段，请使用此选项

class ProfilePage extends StatefulWidget {

  late final String fname;

    ProfilePage({required this.fname});

  @override
  State<ProfilePage> createState() => _ProfilePageState();
}

class _ProfilePageState extends State<ProfilePage> {
  final _form = GlobalKey<FormState>();
  
  late var FullNameController = TextEditingController(text: widget.fname);
  
}

TextEdittingController _controller = new TextEdittingController(text: "your Text");

or

@override
  void initState() {
    super.initState();
    _Controller.text = "Your Text";
    }