jquery mobile 点击两次后退，退出应用

   // @Override    public boolean onKeyDown(int keyCode, KeyEvent event) {        if (keyCode == KeyEvent.KEYCODE_BACK) {           exit();          return true;       }        else        return super.onKeyDown(keyCode, event);    }        //@Override    public void onBackPressed() {    //super.onBackPressed();    return ;    }        public boolean dispatchKeyEvent(KeyEvent event) {            if (event.getKeyCode() == KeyEvent.KEYCODE_BACK ) {                 if (event.getAction() == KeyEvent.ACTION_DOWN && event.getRepeatCount() == 0) {                                   }         if( isClick)         {         isClick = false;         return true;         }                 }        return super.dispatchKeyEvent(event);    }