问微信小程序 wx.opendocument 打不开文件？

wx.downloadFile({

      url: 'https://cynthianc.github.io/images/123.pdf',

      success: function (res) {

        var filePath = res.tempFilePath

        wx.openDocument({

          filePath: filePath,

          success: function (res) {

            console.log('打开文档成功')

            console.log(res)

          },

          fail: function (res) {

            console.log('fail')

            console.log(res)

          },

          complete: function (res) {

            console.log('complete')

            console.log(res)

          }

        })

      },

      fail: function (res) {

        console.log('fail')

        console.log(res)

      },

      complete: function (res) {

        console.log('complete')

        console.log(res)

      }

    })