Flutter TextFormField onChangeText it is not showing icon

Question

I am new in flutter. I am trying to set icon when text changed.

It is not showing icon as I addListner to my controller.

TextEditingController _controller = new TextEditingController();

Defined listner function.

_controller.addListener(() {
  setState(() {}); 
});

TextFormField(                  
  controller: _usernameController,
  decoration: InputDecoration(
    labelText: 'Username',
    suffixIcon: _usernameController.text.length > 0 ? IconButton(
      onPressed: () {
      //do code for button press
      },
      icon: Icon(Icons.check, color: Colors.grey)
    ) : null
  ),
)

Answer 1

You need to add your listener to your _usernameController not your _controller

_usernameController.addListener(() {
  setState(() {}); 
});