I am collecting user input with a TextFormField and when the user presses a FloatingActionButton indicating they are done, I want to dismiss the on screen keyboard.

我正在使用TextFormField收集用户输入，当用户按下FloatingActionButton表示它们已完成时，我想取消屏幕上的键盘。

How do I make the keyboard go away automatically?

如何让键盘自动消失？

import 'package:flutter/material.dart';

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

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

  @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
            _controller.clear();
          });
        },
      ),
      body: new Container(
        alignment: FractionalOffset.center,
        padding: new EdgeInsets.all(20.0),
        child: new TextFormField(
          controller: _controller,
          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());
}

try using a TextEditingController.
at the begining,

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();
  }

and in the on press event,

在新闻发布会上，

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

this will dismiss the keybord.

这将使Keybord失效。

First Connect the TextField with focusNode

首先将Textfield与FocusNode连接起来

 TextField(
focusNode: focusNode),

now for show/open the keyboard call

现在开始显示/打开键盘调用

focusNode.requestFocus();

and for hide/dismiss keyboard call

并用于隐藏/取消键盘调用

 focusNode.unfocus();

and if you want to know keyboard is visible or not at that time check the belew condition

如果您想知道键盘是否可见，请检查Belew条件

final keyBoardVisible = MediaQuery.of(context).viewInsets.bottom != 0;

最终的keyBoardVisible=MediaQuery.of(上下文).viewInsets.Bottom！=0；

here keyBoardVisible value is true if keyboard is visible and false for dismissed keyboard

此处，如果键盘可见，则keyBoardVisive值为True，如果已取消键盘，则值为False

I think there is a easy way.

我认为有一种简单的方法。

set keyboardType: TextInputType.none,

设置键盘类型：TextInputType.one，

TextField(
autofocus: true,
keyboardType: TextInputType.none,

文本字段(AutoFocus：True，KeyboardType：TextInputType.one，

    decoration: InputDecoration(
      border: OutlineInputBorder(),
      labelText: '',
    ),
    controller: _controller,
    
  )

If you use TextField(maxLines: null) and just want to show Done button ON the screen keyboard to hide it, the code below works.

如果您使用Textfield(MaxLines：NULL)，并且只想在屏幕键盘上显示完成按钮来隐藏它，下面的代码可以工作。

TextField(
    keyboardType: TextInputType.text,
    maxLines: null,
)

Side note: why in the first place doesn't the keyboard show Done button? The reason is found in the implementation of TextField:

附注：为什么键盘上一开始没有显示完成按钮？原因可以在Textfield的实现中找到：

keyboardType = keyboardType ?? (maxLines == 1 ? TextInputType.text : TextInputType.multiline),