how to control what happens when text is put in textfield in flutter code example

Example 1: flutter text field

TextField(
  decoration: InputDecoration(
    border: InputBorder.none,
    hintText: 'Enter a search term'
  ),
);

Example 2: edite text in flutter

Widget _editTitleTextField() {  if (_isEditingText)    return Center(      child: TextField(        onSubmitted: (newValue){          setState(() {            initialText = newValue;            _isEditingText =false;          });        },        autofocus: true,        controller: _editingController,      ),    );  return InkWell(    onTap: () {      setState(() {        _isEditingText = true;      });    },    child: Text(  initialText,  style: TextStyle(    color: Colors.black,    fontSize: 18.0,  ), );}