wx.showActionSheet()点击蒙层为什么也会跳转页面？

wx.showActionSheet({

      itemList: [that.data.markName],

      success: function (res) {

        console.log(res.tapIndex)

        wx.navigateTo({

          url: '../shop/detail?id=' + that.data.markId

        })

      },

      fail: function (res) {

        console.log(res.errMsg)

      }

    })