返回键, 长按事件
在Activity中重写方法

@Override  public boolean onKeyLongPress(int keyCode, KeyEvent event) {      if (keyCode == KeyEvent.KEYCODE_CALL) {          // a long press of the call key.          // do our work, returning true to consume it. by          // returning true, the framework knows an action has          // been performed on the long press, so will set the          // canceled flag for the following up event.          return true;      }      return super.onKeyLongPress(keyCode, event);  }