_dismissKeyboard(BuildContext context) {
   FocusScope.of(context).requestFocus(new FocusNode());
}

@override
Widget build(BuildContext context) {

return new GestureDetector(
    onTap: () {
    this._dismissKeyboard(context);
    },
    child: new Container(
    color: Colors.white,
    child: new Column(
        children: <Widget>[/*...*/],
    ),
    ),
 );
}

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

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());
}

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());