How to emptying hint text when focus in TextFormField Flutter

Question

I want to make the hint text in TextFormField disappear when the field focused. But the hint text won't disappear until I insert a character in the field. I did the following. How can I make the hint text disappear when the field focused? Thanks!

Container buildTextField(bool isObscure, TextEditingController textEditingController, String hintText, bool onlyNumber) {
    return Container(
      width: double.infinity,
      height: 60,
      color: MyColors.primary,
      alignment: Alignment.center,
      child: Padding(
        padding: EdgeInsets.only(left: 15, right: 10),
        child: TextFormField(
          textAlign: TextAlign.center,
          keyboardType: onlyNumber ? TextInputType.number : TextInputType.text,
          decoration: InputDecoration(
            hintText: hintText,
            hintStyle: TextStyle(
              color: Colors.white,
              fontWeight: FontWeight.w600,
            ),
            border: InputBorder.none,
          ),
          style: TextStyle(
            color: Colors.white,
            decoration: TextDecoration.none,
            fontWeight: FontWeight.w600,
          ),
          obscureText: isObscure,
          controller: textEditingController,
        ),
      ),
    );
  }

Answer 1

You probably have to add a listener to listen to focus changes:

FocusNode myFocusNode = FocusNode();

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

And then, inside your InputDecoration you update the value:

hintText: myFocusNode.hasFocus ? hintText : ''