How to center text in DropdownButton?

Question

I'm trying to make the DropdownButton hint, text and menu items appear in the center instead of left but TextAlign.center does not seem to be doing anything.

Image of Dropdown with the hint:

Image of Dropdown with the selected item as text:

Image of the Menu items when arrow is pressed:

My code:

return Theme(
  data: ThemeData(canvasColor: blackTrans2, brightness: Brightness.dark),
  child:Container(
    width: MediaQuery.of(context).size.width/1.2,
    decoration: BoxDecoration(
    color: blackTrans,
    borderRadius: BorderRadius.all(Radius.circular(5.0)),
    ),   
    child:DropdownButtonHideUnderline(
      child: ButtonTheme(
        alignedDropdown: true,
        child: DropdownButton(
          value: _dateSelected,
          hint: AutoSizeText(NA_FLIGHT_PAGE_DROPDOWN, style: TextStyle(color: white,),textAlign: TextAlign.center,),
          isDense: false,
          onChanged: (String newValue){
            setState(() {
            _dateSelected = newValue;
            });
          },
          items: snapshot.data.documents.map((DocumentSnapshot document){
            return DropdownMenuItem<String>(
              value: document.documentID,
              child: AutoSizeText(document.documentID, style: TextStyle(color: white,),textAlign: TextAlign.center,),
            );
          }).toList(),
        ),
      ),
    )
  )
);

Not sure if this affects anything but I'm using AutoSizeText in order to resize my text dynamically.

Update: I managed to make the Menu items appear in the center by using Center, but the text and hint is still remains to the left tho even with Center... :

// Does not seem to change the hint or text position (when menu item selected)
hint: Center(child:AutoSizeText(NA_FLIGHT_PAGE_DROPDOWN, style: TextStyle(color: white,),textAlign: TextAlign.center,)),

// Changes the menu item to the center instead of left
child: Center(child:AutoSizeText(document.documentID, style: TextStyle(color: white,),textAlign: TextAlign.center,)),

Answer 1

For those who are seeing option to change flutter class dropdown.dart. You don't need to do that. Do this:

1. set property isExpanded to true
2. use Center widget with DropdownMenuItem class children.

IsExpanded will also take care of overflow.

DropdownButton(
     isExpanded: true,
     value: category_selected,
     items: categories.map<DropdownMenuItem<String>>((var value) {
        return DropdownMenuItem<String>(
          value: value["name"],
          child: Center(
                 child: Text(
                        value["name"],
                        textAlign: TextAlign.center,
                      ),
                    ),
                 );
           }).toList(),
      ),