vue 一个页面多次调用PDF预览组件，全屏状态值异常?

异常截图

父组件

 <el-tab-pane
  v-for="ja in groupResourcesData['电子教案']"
  :key="ja.id"
  :label="`教案:${ja.name}`"
  :name="ja.id + ''"
  >
  <PDFJSViewer :file-url="ja.pdfUrl" />
  </el-tab-pane>

子组件

<template>
  <div id="PDFView" :class="isFullScreen ? 'FullScreen' : ''">
    <iframe height="100%" width="100%" style="min-height: 400px" :src="`${getFilePath}`"></iframe>
  </div>
</template>

<script>
export default {
  name: 'PDFJSViewer',
  props: {
    fileUrl: String,
    path: {
      type: String,
      default: '/lib/pdfjs-2.14.305/web/viewer.html'
    }
  },
  data() {
    return {
      isFullScreen: false
    };
  },
  computed: {
    getFilePath: function () {
      if (this.fileName !== '') {
        return this.path + '?file=' + this.fileUrl;
      }
      return this.path;
    }
  },
  watch: {
    isFullScreen: {
      handler(val) {
        console.log('val', val);
      },
      immediate: true
    }
  },
  // TODO: 有个小问题，每次离开pdfjs状态没有重置
  mounted() {
    this.handleFullScreen();
  },
  methods: {
    handleFullScreen() {
      const iframe = document.querySelector('#PDFView iframe');
      console.log('iframe', iframe);
      // 不兼容IE
      iframe.onload = () => {
        const fullscreen = iframe.contentDocument.querySelector('#fullScreen');
        fullscreen.addEventListener('click', () => {
          this.isFullScreen = !this.isFullScreen;
          console.log('isFullScreen', this);
        });
      };
    }
  }
};
</script>
<style scoped>
#PDFView {
  width: 100%;
  height: 100%;
  min-height: 400px;
}
.FullScreen {
  position: fixed;
  top: 0;
  left: 0;
  z-index: 1000;
  width: 100%;
  height: 100%;
  overflow-y: auto;
  background: #fff;
}
</style>