尝试使用TextEditingController。 一开始，

    final myController = TextEditingController();
     @override
  void dispose() {
    // Clean up the controller when the widget is disposed.
    myController.dispose();
    super.dispose();
  }

在新闻发布会上，

onPressed: () {
            myController.clear();}

这将取消键盘。

这可能会简化情况。下面的代码只在键盘打开时才会工作

if(FocusScope.of(context).isFirstFocus) {
 FocusScope.of(context).requestFocus(new FocusNode());
}

在构建小部件中添加此代码

    FocusScope.of(context).requestFocus(FocusNode());

在Flutter中，一切都是一个小部件，我决定包装FocusScope.of(context).unfocus();在一个简短的实用程序小部件中实现。

只需创建KeyboardHider小部件:

import 'package:flutter/widgets.dart';

/// A widget that upon tap attempts to hide the keyboard.
class KeyboardHider extends StatelessWidget {
  /// Creates a widget that on tap, hides the keyboard.
  const KeyboardHider({
    required this.child,
    Key? key,
  }) : super(key: key);

  /// The widget below this widget in the tree.
  final Widget child;

  @override
  Widget build(BuildContext context) {
    return GestureDetector(
      behavior: HitTestBehavior.opaque,
      onTap: () => FocusScope.of(context).unfocus(),
      child: child,
    );
  }
}

现在，您可以用KeyboardHider小部件包装任何小部件(在使用好的IDE时非常方便)，然后当您点击某个东西时，键盘将自动关闭。它与表单和其他可点击区域一起工作得很好。

class SimpleWidget extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return KeyboardHider(
      /* Here comes a widget tree that eventually opens the keyboard,
       * but the widget that opened the keyboard doesn't necessarily
       * takes care of hiding it, so we wrap everything in a
       * KeyboardHider widget */
      child: Container(),
    );
  }
}

下面的代码帮助我隐藏键盘

   void initState() {
   SystemChannels.textInput.invokeMethod('TextInput.hide');
   super.initState();
   }

你也可以为你的文本域声明一个focusNode，当你完成时，你可以在那个focusNode上调用unfocus方法 然后处理它

class MyHomePage extends StatefulWidget {
  MyHomePageState createState() => new MyHomePageState();
}

class MyHomePageState extends State<MyHomePage> {
  TextEditingController _controller = new TextEditingController();

/// declare focus
  final FocusNode _titleFocus = FocusNode();

  @override
  void dispose() {
    _titleFocus.dispose();
  }

  @override
  Widget build(BuildContext context) {
    return new Scaffold(
      appBar: new AppBar(),
      floatingActionButton: new FloatingActionButton(
        child: new Icon(Icons.send),
        onPressed: () {
          setState(() {
            // send message
            // dismiss on screen keyboard here

            _titleFocus.unfocus();
            _controller.clear();
          });
        },
      ),
      body: new Container(
        alignment: FractionalOffset.center,
        padding: new EdgeInsets.all(20.0),
        child: new TextFormField(
          controller: _controller,
          focusNode: _titleFocus,
          decoration: new InputDecoration(labelText: 'Example Text'),
        ),
      ),
    );
  }
}