title: How to get value from TextFormField on Flutter
body: <p>I would like to get input value from TextFormField.
  And then I want to take it into Firebase.</p>
  
  <p>If I have three TextFormField (last_name / first_name / birthday), how can I get these value and throw them into firebase?</p>
  
  <p><a href="https://i.stack.imgur.com/rXh17.png" rel="noreferrer"><img src="https://i.stack.imgur.com/rXh17.png" alt="enter image description here"></a></p>
  
  <ul>
  <li>I had already connect and get values from firebase.</li>
  </ul>