自定义事件fire问题

<script type="text/javascript">  
            mui.init();  

            var targetPage = mui.preload({  
                url:'sub.html',  
                id:'sub'  
            });   

            mui.plusReady(function () {  
                mui('.mui-table-view').on('tap','a',function(){  
                    // mui.alert(this.innerHTML);  
                    // alert(this.getAttribute('id'));  
                    mui.fire(targetPage,'newsId',{  
                        title:this.innerHTML,  
                        id:this.getAttribute('id')  
                    });  

                    mui.openWindow({  
                        url:'sub.html',  
                        id:'sub'  
                    });  
                });  

            })  
        </script>  

<script type="text/javascript">  
            mui.init();  
            window.addEventListener('newsId',function(event){  
              //获得事件参数  
              var id = event.detail.id;  
              //根据id向服务器请求新闻详情  
              mui.toast(id);  
            });  

        </script>

到子页面时没反应,是fire事件没被触发吗?哪里代码有问题?