document.addEventListener('plusready', function (a) {
    var first = '';
    plus.key.addEventListener('backbutton', function () {
      //获取地址栏目中的url
      var urls = location.hash.split('/')[1]
      if (urls === 'index') {//判断是首页的时候点击二次退出app
        if (new Date().getTime() - first < 3000) {
          // console.log("关闭程序")
          plus.runtime.quit();
        } else {
          alertMsg("再按一次退出应用");//自定义的弹窗
          first = new Date().getTime();
        }
      } else {
        history.go(-1)
      }
    }, false);
  });

在vue项目的index.html文件中放入上面的js代码

plus.key.addEventListener是用hbuilder打包后hbuilder提供的接口，想了解可以参考（http://www.hcoder.net/tutorials/info_1279.html）

plus.runtime.quit();是退出app的意思

自定义退出窗(alertMsg()方法)的代码如下：

 window.alertMsg = function (txt) {
    var alertFram = document.createElement("DIV");
    alertFram.id = "alertFram";
    alertFram.style.position = "fixed";
    alertFram.style.width = "100%";
    alertFram.style.textAlign = "center";
    alertFram.style.bottom = "10%";
    alertFram.style.zIndex = "10001";
    strHtml = " <span style=\"font-family: 微软雅黑;font-size:0.75rem;display:inline-block;background:#333;color:#fff;padding:0 0.625rem;line-height:2.25rem;border-radius:0.375rem; \">" + txt + "</span>";
    alertFram.innerHTML = strHtml;
    document.body.appendChild(alertFram);
    setTimeout((function () {
      alertFram.style.display = "none";
    }), 2000);
  };