你好，我想问一下保存了进度但是百分比不能更新的问题。
代码如下，在mounted的时候调用initPage方法

initPage () {
      this.book.ready.then(() => {
        return this.book.locations.generate(750 * (window.innerWidth) / 375) * (getFontSize(this.setFileName) / 16)
      }).then((res) => {
        this.setBookAvailable(true)
        this.refreshLocation()
      })
    },

refreshLocation的代码如下

refreshLocation () {
      console.log(this.currentBook.rendition.currentLocation())
      const currentLocation = this.currentBook.rendition.currentLocation()
      const startCfi = currentLocation.start.cfi
      const progress = this.currentBook.locations.percentageFromCfi(startCfi)
      this.setProgress(Math.floor(progress * 100))
      setLocation(this.fileName, startCfi)
    },

报错如下
Uncaught (in promise) TypeError: Cannot read property ‘currentLocation’ of undefined