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(),
    );
  }
}

看起来不同的版本用不同的方法。我使用的是Flutter v1.17.1，下面的操作适合我。

onTap: () {
    FocusScopeNode currentFocus = FocusScope.of(context);
    if (!currentFocus.hasPrimaryFocus && currentFocus.focusedChild != null) {
       currentFocus.focusedChild.unfocus();
    }
}

我已经创建了这个函数到我的基本代码，到目前为止工作得很好!!

void hideKeyword(BuildContext context) {
  FocusScopeNode currentFocus = FocusScope.of(context);
  if (!currentFocus.hasPrimaryFocus && currentFocus.focusedChild != null) {
    currentFocus.focusedChild.unfocus();
  }
}

如果你的键盘仍然不会关闭，不要忘记添加focusNode到TextField。上面的信息很有帮助，但是忘记添加focusNode让我有点困扰。这里有一个例子。

TextField(
          focusNode: FocusNode(),
          textController: _controller,
          autoFocus: false,
          textStyle: TextStyle(fontSize: 14),
          onFieldSubmitted: (text) {},
          onChanged: (text) {},
          hint: 'Enter the code',
          hintColor: CustomColors.mediumGray,
          suffixAsset: _voucherController.text.length == 7
              ? Assets.ic_approved_voucher
              : null,
          isIcon: false,
          isObscure: false,
          maxLength: 7,
        )



closeKeyboard(BuildContext context) {
    var currentFocus = FocusScope.of(context);
    if (!currentFocus.hasPrimaryFocus) {
      currentFocus.unfocus();
    }
  }

  @override
  Widget build(BuildContext context) {
    _keyboardVisible = MediaQuery.of(context).viewInsets.bottom != 0;
    size = MediaQuery.of(context).size;
    return GestureDetector(
      onTap: () {
        closeKeyboard(context);
      },
      child: Scaffold(
        backgroundColor: Colors.white,
        body: Container(
            width: double.maxFinite,
            height: double.maxFinite,
            child: _buildUI(vm)),
      ),
    );
  }

如果你使用CustomScrollView，只要放，

keyboardDismissBehavior: ScrollViewKeyboardDismissBehavior.onDrag,

您可以使用FocusNode类中的unfocus()方法。

import 'package:flutter/material.dart';

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

class MyHomePageState extends State<MyHomePage> {
  TextEditingController _controller = new TextEditingController();
  FocusNode _focusNode = new FocusNode(); //1 - declare and initialize variable

  @override
  Widget build(BuildContext context) {
    return new Scaffold(
      appBar: new AppBar(),
      floatingActionButton: new FloatingActionButton(
        child: new Icon(Icons.send),
        onPressed: () {
            _focusNode.unfocus(); //3 - call this method here
        },
      ),
      body: new Container(
        alignment: FractionalOffset.center,
        padding: new EdgeInsets.all(20.0),
        child: new TextFormField(
          controller: _controller,
          focusNode: _focusNode, //2 - assign it to your TextFormField
          decoration: new InputDecoration(labelText: 'Example Text'),
        ),
      ),
    );
  }
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return new MaterialApp(
      home: new MyHomePage(),
    );
  }
}

void main() {
  runApp(new MyApp());
}