Android: how do I use\call custom AlertDialog with MapView Overlays?

Question

Hello and thanks for the help.

I am using the following code to generate a generic AlertDialog on my MapView Overlay (all is working)....I would like to know how or what to change to call a custom AlertDialog called custom.xml

   @Override
    protected boolean onTap(int i) 
    {

        //final Dialog dialoggg = new Dialog(mContext);
//      dialoggg.setContentView(R.layout.custom);
//        LayoutInflater inflater = LayoutInflater.from(mContext);
//        View dialogview = inflater.inflate(R.layout.custom, null);

        //when you tap on the marker this will show the informations provided by you when you create in the
        //main class the OverlayItem
        OverlayItem item = mOverlays.get(i);
        AlertDialog.Builder builder = new AlertDialog.Builder(mContext);
        builder.setMessage(item.getSnippet())
               .setTitle(item.getTitle())
               .setCancelable(true)
               .setPositiveButton("View Details", new DialogInterface.OnClickListener() {

                   public void onClick(DialogInterface dialog, int id) {
                       Intent intent = new Intent(new Intent("com.GoGoGo.Play.LINEUP"));
                       mContext.startActivity(intent);
                   }
               })
               .setNegativeButton("Close window", new DialogInterface.OnClickListener() {
                   public void onClick(DialogInterface dialog, int id) {
                       dialog.dismiss();
                   }
               });
        AlertDialog alert = builder.create();
        alert.show();
        return true;
    }

Nothing too fancy really I just want to change the background color of the AlertDialog to black...(from the standard gray).

Your time and help are greatly appreciated. -thx