background-attachment:fixed;在pc端有效，移动端无效，解决如下：

body:before {
      content: ' ';
      position: fixed;
      z-index: -1;
      top: 0;
      right: 0;
      bottom: 0;
      left: 0;
      background: url(...) center 0 no-repeat;
      background-size: cover;
    }

pushHistory();
    window.addEventListener("popstate", function(e) {
        window.location = "{php echo $this->createMobileUrl('goindex',array())}";
    }, false);
    function pushHistory() {
        var state = {
            title: "title",
            url: "#"
        };
        window.history.pushState(state, "title", "#");
    }
    XBack.listen(function(){
        alert('back');
    });