同步下载多个图片    downloadFile(url) {     const that = this;     return new Promise(function (resolve) {       wx.downloadFile({         url,         success: function (downRes) {           if (downRes.statusCode === 200) {             wx.getImageInfo({               src: downRes.tempFilePath,               success: function (info) {                 resolve({ info, url: downRes.tempFilePath });               }             });           }         }       });     });   },   downloadFileList(list) {     const that = this;     let pList = [];     for (let i = 0; i < list.length; i++) {       pList[i] = that.downloadFile(list[i]);     }     return Promise.all(pList);   }, that.downloadFileList(imgList).then(urlList => {     //...todo... });