I'm trying to set a custom typeface to a dialog built using [AlertDialogPro](https://github.com/fengdai/AlertDialogPro) but get a NPE when trying to retrieve the dialog Button using `dialog.getButton(int)`. And how can I set the typeface for the message and title of the dialog?

```
AlertDialogPro.Builder builder = new AlertDialogPro.Builder(this);
   builder.setMessage(getResources().getString(R.string.dialog_body))
   .setPositiveButton(getResources().getString(R.string.ok), new DialogInterface.OnClickListener() {
      @Override
      public void onClick(DialogInterface dialog, int which) {
          // Do stuff
      }
});

AlertDialogPro dialog = builder.create();
dialog.getButton(DialogInterface.BUTTON_POSITIVE).setTypeface(customTf));
dialog.show();

```

Log:

```
03-02 16:30:22.982: E/AndroidRuntime(15596): 
java.lang.NullPointerException: Attempt to invoke virtual method 'void android
.widget.Button.setTypeface(android.graphics.Typeface)' on a null
object reference

```