在Android中更新警报对话框标题

我在片段活动中使用了带有标题的警报对话框。在单独的类中创建了警报对话框。

当我单击警报对话框中的按钮时，我必须更新标题名称？？？

下面显示了警报对话框代码

public  class ViewCartDialog 
{
 Activity activity;
 Cursor cursor;
 public static AlertDialog.Builder builder;
 public ViewCartDialog(Activity activity)
 {
  this.activity=activity;
  cartDialog();
 }
 public void cartDialog() 
 {
  // TODO Auto-generated method stub
   builder = new AlertDialog.Builder(activity);
      //  builder.setIcon(R.drawable.shopping_cart);
   cursor = DBCatalog.getCursor();
        builder.setTitle("My Carts"+"("+cursor.getCount()+")");
        LayoutInflater adbInflater = LayoutInflater.from(activity);
     View cartview = adbInflater.inflate(R.layout.cart_list, null);
     final EditText custcode=(EditText) cartview.findViewById(R.id.cust_codefield);
     final EditText custname=(EditText) cartview.findViewById(R.id.cust_namefield);
     custcode.setOnTouchListener(new DrawableClickListener.RightDrawableClickListener(
       custcode) {
   @Override
   public boolean onDrawableClick() {
    new Customer(activity,custcode,custname);
    return true;

   }

  });
        ListView cart_lv=(ListView) cartview.findViewById(R.id.cart_list);
        CartAdapter cartadapter=new CartAdapter(activity, R.layout.cart_listitem, cursor);
        cart_lv.setAdapter(cartadapter);
        builder.setView(cartview);
     builder.setNegativeButton("cancel",
                new DialogInterface.OnClickListener() {

                    @Override
                    public void onClick(DialogInterface dialog, int which) {
                        dialog.dismiss();
                    }
                });

        builder.setPositiveButton("Place Order",
                new DialogInterface.OnClickListener() {

                    @Override
                    public void onClick(DialogInterface dialog, int which) {

                    }
                });
        builder.show();
 }
}