downVideo(url){
      var that = this
      tt.showLoading({
        title: '准备中...'
      });
      tt.downloadFile({
        url,
        success: (res) => {
          console.log("临时文件下载成功,下载路径: " + res.tempFilePath);
          tt.hideLoading();
          that.setData({
            videoUrl: res.tempFilePath
          })
        }})
    }