Android：如何创建模态进度“轮”叠加？

ProgressDialog接近,但我不想要对话框背景或边框.

我尝试设置对话框窗口的背景drawable：

this.progressDialog = new ProgressDialog(Main.this);

this.progressDialog.getwindow().setBackgroundDrawable(new ColorDrawable(0));
this.progressDialog.setProgressstyle(ProgressDialog.STYLE_SPINNER);
this.progressDialog.setCancelable(false);
this.progressDialog.setIndeterminate(true);

this.progressDialog.show();

但无济于事(即看起来仍然没有… setBackgroundDrawable代码).