How to extend the line under text form field till under visibility icon?

Question

I have a text form field to enter password, I have added a visibility icon button with the field in a row. How do I extend the underline till under the icon? (There is a validator in the text form field, so I want the exact same line extended so that the behavior is same).

Answer 1

Define the IconButton as a prefixIcon within the TextFormField:

child: TextFormField(
  decoration: InputDecoration(
    prefixIcon: IconButton(
      icon: Icon(Icons.visibility),
      onPressed: () {},
    ),
  ),
  ...
),