主题：hbuilder生成app，屏蔽返回键退出程序失败，求指点。

web/weui目录下weui.me.js文件，修改onload函数

function onload() {
    var eles = document.getElementsByClassName("weui_mask_transition");
    for (var i = 0; i < eles.length; i++) {
  eles[i].addEventListener("transitionend", hideActionMask);
    } 
 eles=document.getElementsByClassName("fox_table")
 for (var i = 0; i < eles.length; i++) {
  eles[i].onmousedown=tableMouseDown;
  eles[i].rowSel = -1;
  eles[i].colSel = -1;
  if(eles[i].hasAttribute("data-pagenumber")){
   eles[i].pagenumber=eles[i].attributes["data-pagenumber"].value;
  }
 }
 eles = document.getElementsByClassName("weui-gallery__img");
    for (var i = 0; i < eles.length; i++) {
        eles[i].onclick = galleryClick;
    }
 eles = document.querySelectorAll(".weui_uploader_files,.article_image");
 for (var i = 0; i < eles.length; i++) {
        eles[i].onclick = showGallery;
    }
 eles = document.querySelectorAll("[data-tab-page]");
 for (var i = 0; i < eles.length; i++) {
        eles[i].onclick = tabClick;
    }
 eles = document.querySelectorAll(".fox_actionsheet,.weui_dialog_ft");
 for (var i = 0; i < eles.length; i++) {
        eles[i].onclick = hide;
    }
 eles = document.getElementsByClassName("weui-gallery__del");
 for (var i = 0; i < eles.length; i++) {
        eles[i].onclick = galleryDelete;
 } 
 eles=document.getElementsByTagName("form");
 for(var i=0;i<eles.length;i++){
  if(eles[i].querySelector(".weui_uploader_input[data-incremental]")){
   eles[i].incremental = true;
   eles[i].onreset=resetForm;
   var fluds=eles[i].getElementsByClassName("weui_uploader_input");
   for(var idx=0;idx<fluds.length;idx++){
    fluds[idx].Files = [];
   }
  }
 }
 var eles = document.getElementsByClassName("weui_uploader_input");
    for (var i = 0; i < eles.length; i++) {
  if (!eles[i].Files){
   eles[i].onchange = previewFile;
   }
  else{
   if(eles[i].hasAttribute("data-scalewidth") || eles[i].hasAttribute("data-scaleheight")){
    eles[i].onchange = previewFile3;
   }
   else {eles[i].onchange = previewFile2;}
  }
    }

    document.addEventListener("plusready", function() {
        var webview = plus.webview.currentWebview();
        plus.key.addEventListener('backbutton', function() {
        webview.canBack(function(e) {
            if(e.canBack) {
                webview.back();
            } else {
                plus.nativeUI.confirm("退出程序？", function(event) {
                    if (event.index) {
                        plus.runtime.quit();
                    }
                }, null, ["取消", "确定"]);
                //webview.close(); //hide,quit
                //plus.runtime.quit();
            }
        })
        });
    });
}