安卓真机，canvas导出的图片为什么是透明底色，而开发工具跟ios是正确的白色地图？

贴代码，如下：

canvasToImage () {

      mpvue.canvasToTempFilePath({

        x: 0,

        y: 0,

        canvasId: ‘shareCanvas’,

        fileType: ‘jpg’,

        quality: 1,

        success: res => {

          console.log(res)

          wx.saveImageToPhotosAlbum({

            filePath: res.tempFilePath,

            success (res) {

              console.log(res)

              showModal({

                content: ‘图片已保存到相册，赶紧去朋友圈分享吧~’

              })

            }

          })

        }

      })

    }