How to disable mobile keyboard action key using Flutter?

You have a couple of options.

You can create a new focus:

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

Example:

Widget build(BuildContext context) {
  return Scaffold(
    body: SafeArea(
      child: GestureDetector(
        onTap: () {
          FocusScope.of(context).requestFocus(new FocusNode());
        },
        child: ....,    
      )
    )
  )
}

The other option is to release the existing focus:

FocusScopeNode currentFocus = FocusScope.of(context);

if (!currentFocus.hasPrimaryFocus) {
    currentFocus.unfocus();
}

There is also a package: keyboard_dismisser

You just need to add a FocusNode to your TextFormField and request focus for it if the user presses the submit button on the keyboard when the field is empty. Here is a complete example:

class KeyboardKeeper60943209 extends StatefulWidget {
  @override
  _KeyboardKeeper60943209State createState() => _KeyboardKeeper60943209State();
}

class _KeyboardKeeper60943209State extends State<KeyboardKeeper60943209> {
  List<String> items = List.generate(20, (index) => 'item $index');
  TextEditingController _textEditingController = TextEditingController();
  FocusNode _focusNode = FocusNode();

  @override
  Widget build(BuildContext context) {
    return Column(
      children: <Widget>[
        Row(
          children: <Widget>[
            Expanded(
              child: TextFormField(
                focusNode: _focusNode,
                controller: _textEditingController,
                decoration: InputDecoration(
                  prefixIcon: Icon(Icons.search),
                  labelText: 'Search',
                  hasFloatingPlaceholder: false,
                ),
                // This is the key part
                onFieldSubmitted: (value) {
                  if(value == ''){
                    _focusNode.requestFocus();
                  }
                },
              ),
            ),
            FlatButton(onPressed: search, child: Text('Search'))
          ],
        ),
        Expanded(
          child: Container(
            child: ListView.builder(
              itemBuilder: (context, index){
                return ListTile(
                  title: Text(items[index]),
                  subtitle: Text(items[index]),
                );
              }
            ),
          ),
        ),
      ],
    );
  }

  void search(){
    print('search');
  }
}

TextFormField(
                  readOnly: true,
                  showCursor: false,
                  controller: consName,
                  decoration: InputDecoration(
                    hintText: 'Enter Name',
                    labelText: 'Username',
                    focusedBorder: OutlineInputBorder(
                      borderSide: BorderSide(
                        color: Colors.deepPurple,
                        width: 2,
                      ),
                    ),
                  ),
                ),

Very Simple & Easy Use "readOnly: true" for disabling keyboard and if you don't want pointer or cursor then "showCursor: false". That's it, hope this'll work. Eat Sleep Workout Code Repeat. Happy Coding.

You can simply use textInputAction: TextInputAction.none on the TextField.