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());
}

下面的代码帮助我隐藏键盘

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

总之，这是Flutter 1.17的工作解决方案:

像这样包装你的Widget:

GestureDetector(
        onTap: FocusScope.of(context).unfocus,
        child: YourWidget(),
);

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(),
    );
  }
}

GestureDetector(
          onTap: () {
            FocusScope.of(context).unfocus();
          },
          child:Container(
    alignment: FractionalOffset.center,
    padding: new EdgeInsets.all(20.0),
    child: new TextFormField(
      controller: _controller,
      decoration: new InputDecoration(labelText: 'Example Text'),
    ),
  ), })

试试这个动作

注意:这个答案已经过时了。有关Flutter的新版本，请参阅答案。

你可以通过把TextFormField的焦点拿走，并把它给一个未使用的FocusNode来解散键盘:

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