picker 我照着文档和demo写的为什么点不出菜单呢？

如题

        <style>  
            .mui-btn {  
                font-size: 16px;  
                padding: 8px;  
                margin: 3px;  
            }  

            h5.mui-content-padded {  
                margin-left: 3px;  
                margin-top: 20px !important;  
            }  

            h5.mui-content-padded:first-child {  
                margin-top: 12px !important;  
            }  
        </style>  
        <script src="js/mui.min.js"></script>  
        <script type="text/javascript" src="js/mui.picker.js"></script>  
        <script type="text/javascript" src="js/mui.poppicker.js"></script>  
        <link href="css/mui.min.css" rel="stylesheet" />  
        <link href="css/mui.picker.css" rel="stylesheet" />  
        <link href="css/mui.poppicker.css" rel="stylesheet" />  
        <script type="text/javascript" charset="utf-8">  
            mui.init();  
            mui.plusReady(function() {  
//              var _getParam = function(obj, param) {  
//                  return obj[param] || '';  
//              };  
                //普通示例  
                var userPicker = new mui.PopPicker();  
                userPicker.setData([{  
                    value: 'ywj',  
                    text: '董事长 叶文洁'  
                }, {  
                    value: 'aaa',  
                    text: '总经理 艾AA'  
                }, {  
                    value: 'lj',  
                    text: '罗辑'  
                }, {  
                    value: 'ymt',  
                    text: '云天明'  
                }]);  
                var showUserPickerButton = doc.getElementById('showUserPicker');  
//                  var userResult = doc.getElementById('userResult');  
                    showUserPickerButton.addEventListener('tap', function(event) {  
                        this.userPicker.show(function(items) {  
//                          userResult.innerText = JSON.stringify(items[0]);  
                            //返回 false 可以阻止选择框的关闭  
                            //return false;  
                        });  
                    }, false);  
            });  
        </script>