How to show label and error message inside the boundry of textformfield in flutter?

Question

I'm using a text and textformfield inside a container to get userName. I need to do the text field validation and get the error message and red color boundary box as shown in expected outcome image. I have included the current output also. I tried a few other ways also. But nothing worked.

Current output

Expected Output

    decoration: BoxDecoration(
        borderRadius: BorderRadius.all(Radius.circular(10)),
        shape: BoxShape.rectangle,
        color: Color(0xFFF4F9FE),
      ),
      child: Column(
        crossAxisAlignment: CrossAxisAlignment.start,
        children: <Widget>[
          Padding(
            padding: const EdgeInsets.fromLTRB(10, 3, 0, 0),
            child: Text("Full Name",
              style: TextStyle(color: Color(0xFFA8C3EC)),
            ),
          ),
          Padding(
            padding: const EdgeInsets.fromLTRB(10, 0, 10, 0),
            child: TextFormField(
              decoration: new InputDecoration(
                hintText: "Enter Your Full Name",
                border: InputBorder.none,
                focusedBorder: InputBorder.none,
                enabledBorder: InputBorder.none,
                errorBorder: OutlineInputBorder(
                  borderRadius: BorderRadius.circular(10.0),
                  borderSide: BorderSide(color:  Colors.red),
                ),
                disabledBorder: InputBorder.none,
                contentPadding: const EdgeInsets.symmetric(vertical: 1.0),
              ),
              validator: _validateName,
            ),
          ),
        ],
      ),
    );

String _validateName(String value) {
    return "Required field cannot be empty";
}