怎么改变progressDialog消息字体字号

void setProgressDialogText(ProgressDialog mprogressDialog)
  {
     View v = mprogressDialog.getWindow().getDecorView();   //取得dialog的整个view
      setDialogText(v);   //对view进行设置
  }

  private void setDialogText(View v) { 
     if (v instanceof ViewGroup) {
       ViewGroup parent = (ViewGroup) v;
       int count = parent.getChildCount();
       Log.d(TAG,"*******$$$*************child count="+count);
       for (int i = 0; i < count; i++) {
         View child = parent.getChildAt(i);
         setDialogText(child);
       }
     } else if (v instanceof TextView) {
       Log.d(TAG,"......................999txtsize="+((TextView) v).getTextSize());
       ((TextView) v).setTextSize(40); //遍历所有的view，找到textview，设置字体大小
     }
   }