oblige user to fill edittext

Speak Carlos,

You are inflating an xml with the items of your actionBar, correct?

Something like this:

@Override
public void onCreateOptionsMenu(Menu menu, MenuInflater inflater) {
   super.onCreateOptionsMenu(menu, inflater);
   inflater.inflate(com.sample.R.menu.menu_main, menu);
}

So, you have to have a method that controls the clicks, for example:

public boolean OnOptionItemSelected(MenuItem item){
    switch(item.getItemId()){
      case R.id.enviarForm:
          //verifica se o campo de texto está nulo
          return true;  
      default:
         return super.onOptionsItemSelected(item);
    }   
}

Hugs.

But I would put a method, which checks whether the field is null or not, to be activated when the user clicks on the Button.

Take a look at this link. I hope it helps. When validating fields in a form in swing?