如何屏蔽back鍵，當點擊back鍵時Dialog對話框不消失

mSaveingProgressDialog.setOnKeyListener(mDialogOnKeylistener);    

DialogInterface.OnKeyListener mDialogOnKeylistener = new DialogInterface.OnKeyListener(){
        public boolean onKey(DialogInterface dialog, int keyCode, KeyEvent event) {
            if (mSaveing) {
                if (KeyEvent.KEYCODE_BACK == keyCode) {
                    return true;
                }
            }
            return false;
        }
    } ;