Question

I want the message text within my dialog box to be center aligned.

Answer 1

Create your own TextView object and then supply it to popup builder as View:

AlertDialog.Builder popupBuilder = new AlertDialog.Builder(this);
TextView myMsg = new TextView(this);
myMsg.setText("Central");
myMsg.setGravity(Gravity.CENTER_HORIZONTAL);
popupBuilder.setView(myMsg);

You can control all other text parameters (style, color, size …). To control margins you may programatically create LinearLayout, set LayoutParams, and then put TextView into it.