你可以用"GestureDetector"来包装你的小部件，然后将"FocusScope.of(context).unfocus()"赋值给它的onTap函数

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

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'),
        ),
      ),
    );
  }
}

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());

FocusScope.of(context).unfocus()在与过滤后的listView一起使用时有一个缺点。 除了这么多细节和简洁，使用https://pub.dev/packages/keyboard_dismisser中的keyboard_disser包将解决所有问题。

取消键盘(1.7.8+热修复。2和以上)只需调用下面的方法:

FocusScope.of(context).unfocus();

一旦FocusScope.of(context).unfocus()方法在解散键盘之前检查是否有焦点，就不需要检查它了。但如果你需要它，只需调用另一个上下文方法:FocusScope.of(context).hasPrimaryFocus

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());
}