以下是后台定位代码   startLocationChange() {     const that = this     const d = new Date()     //检查是否已开启后台定位请求     if (!APP.globalData.startLocation) {       wx.startLocationUpdateBackground({         success: (res) => {           APP.globalData.startLocation = true           wx.offLocationChange((result) => {})           wx.onLocationChange((result) => {             const second = d.getSeconds()             if (second % 30 === 0) {               const markers = that.data.markers               const polyline = that.data.polyline               const timestamp = d.getTime()               //获取本地points缓存并存入变量               let points = wx.getStorageSync('points')               points = points ? JSON.parse(points) : []               if (Object.keys(result).length > 0) {                 markers[0].latitude = result.latitude.toFixed(6)                 markers[0].longitude = result.longitude.toFixed(6)                 that.setData({                   markers                 })               }               //设置缓存用于5分钟上传               points.push({                 latitude: markers[0].latitude,                 longitude: markers[0].longitude,                 timestamp: parseInt(timestamp / 1000)               })               wx.setStorage({                 key: 'points',                 data: JSON.stringify(points)               })               //合并30秒获取的points数据到polyline               polyline[0].points.push({                 latitude: markers[0].latitude,                 longitude: markers[0].longitude,                 timestamp: parseInt(timestamp / 1000)               })               that.setData({                 polyline               })             }           })         },         fail: (res) => {           console.log(res);         }       })     }   },

我现在做的一个业务也是，同样的素材media_id变了。请问是啥原因