AngularJS一个Demo省市三级联动问题，联动页面不显示

[璞瑜无文]

1.View里代码如下：

 <div class="form-group" ng-controller="CitySelectedContrller as vm">
                        
                            
                            <select name="provinceList" class="provinceList"   ng-model="provinceList.id" ng-change="vm.provinceListChange(provinceList.id);cityList.id='1';" ng-options="obj.id as obj.name for obj in vm.provinceList"><option value="">-- 省份 --</option></select>

                            <select name="cityList" class="cityList"   ng-model="cityList.id" ng-change="vm.cityListChange(cityList.id);" ng-options="obj.name for obj in vm.cityList"><option value="">-- 市区 --</option></select>

                            <select name="areaList" class="areaList"   ng-model="areaList.id" ng-change="vm.areaListChange(areaList.id);" ng-options="obj.name for obj in vm.areaList"><option value="">-- 区县 --</option></select>


                        </div>

2.根据封装好的AngularJS。先注册app.然后实现controller。
$$page("cityselected.controller", {


//创建数据上下文中的绑定数据
_controller: function(vm, scope) {

this._vm.provinceList = provinces; //省份素具

getCityListByProvince = null;

this._vm.cityList = getCityListByProvince; //城市数据

getAreaListByProvince = null;

this._vm.areaList = getAreaListByProvince; //城市数据

},

_initCallback: function(index) {
var self = this;


self._vm.provinceListChange = function (index) {

self._provinceListChange(index);
};
self._vm.cityListChange = function (index) {

self._cityListChange(index);
};
self._vm.areaListChange = function (index) {

self._areaListChange(index);
};

},
_provinceListChange: function (index) {

getCityListByProvince = GetCityByProvinceid(index);
this._vm.cityList = getCityListByProvince;
},
_cityListChange: function (index) {
getAreaListByProvince = GetAreasByCityid(index);
this._vm.areaList = getAreaListByProvince;
},
_areaListChange: function (index) {

},
});

angular.module('myApp').controller('CitySelectedContrller', $$page.cityselected_controller);

$$page.cityselected_controller.$inject = ['$scope'];

问题在于：
如下这个Function：
_provinceListChange: function (index) {

getCityListByProvince = GetCityByProvinceid(index);
this._vm.cityList = getCityListByProvince;
},

当页面改变触发这个方法 cityList 重新赋值，在调试中cityList 已经赋值，但是页面上没有反应。