类型：脚本错误

错误样例: undefined is not an object (evaluating ‘a.mapCtx.getCenterLocation’);at pages/location/location page regionchange function

以下是相关代码：

.js:

regionchange:function(e){

    var that = this;

      if(e.type=='end'){

        // this.getCenterLocation();

        that.mapCtx.getCenterLocation({

            success: function (res) {

                that.setData({

                    m_latitude: res.latitude,

                    m_longitude: res.longitude

                })

                that.requestData(res.longitude, res.latitude, 0);

            }

        })

      }

},

.wxml

<map wx:if="{{show_tab_list==0}}" id=“aokeNear” longitude="{{longitude}}" latitude="{{latitude}}"  markers="{{markers}}"  bindmarkertap=“onMarkerClick” scale=“15” show-location=“true” bindregionchange=“regionchange” controls="{{controls}}" bindcontroltap=“bindcontrol”>

</map>

代码很简单，逻辑也很简单，不知道是什么原因造成的告警。有没有知道的朋友，麻烦帮忙看看，万分感谢~