當點選返回按鈕，或者退出按鈕時，提示使用者重新確定是否要退出當前Activity：

@Override
public void onBackPressed() {
	// TODO Auto-generated method stub
	AlertDialog.Builder builder = new Builder(UpnpMainAct.this);
	builder.setMessage("確認退出程式？");
	builder.setTitle("提示");
	builder.setPositiveButton("確認", new DialogInterface.OnClickListener() {

		@Override
		public void onClick(DialogInterface dialog, int which) {

			finish();
		}
	});
	builder.setNegativeButton("取消", null);

	builder.create().show();
}