wx.downloadFile({

      url: 'https://test.tiedoo.com/web/workbench/c/specialissue/createCataQrcode?download=true&cataId=54a8035f0cf21f30929a0038',

      success: res => {

        console.log(res)//???

        wx.previewImage({

          urls: [res.tempFilePath],

        })

      }

输出：

Object {statusCode: 500, errMsg: "downloadFile:ok"}