I am afraid you can't do this. But one thing is you can handle the softkeyboard keyevents like this,
edittext.setOnKeyListener(new OnKeyListener() {
        public boolean onKey(View v, int keyCode, KeyEvent event) {
                if (event.getAction() == KeyEvent.ACTION_DOWN
                        && event.getKeyCode() ==       KeyEvent.KEYCODE_ENTER) {
                    Log.i("event", "captured");
                    return false;
                } 
                else if(event.getAction() == KeyEvent.ACTION_DOWN
                        && event.getKeyCode() == KeyEvent.KEYCODE_BACK){
                    Log.i("Back event Trigered","Back event");
                }
            }
            }
            return false;
        }
    });
Apart from this, you have to note that providing the attribute android:singleLine=true will make your edittext from growing in size when the soft keyborad ENTER is pressed