[vue ]滚动视图解决ElementUI NavMenu 导航菜单过长显示的问题

记录一下工作

需求

　　导航菜单过长的时候会溢出，需要一个像 Tabs 标签页一样的滚动视图容器，可以左右滚动内部视图。

 

解决方法

　　由于时间问题，所以直接将 Tabs 源码抽取出来使用。

　　这里要做一些特殊处理，不允许 NavMenu 导航菜单滚动视图容器内的元素换行。

如： 

/deep/.el-menu--horizontal>.el-menu-item,.el-menu--horizontal>.el-submenu {

    float: none !important;

    display: inline-block !important;

  }

使用方法如下：

<scrollView>
    <div>
      // 一些不换行内容      
    </div>
</scrollView>

 

最后效果

下面是抽出来的源码，稍稍改造了下，左右箭头做了自适应垂直居中，把 elementui的样式抽取出来以及修改了类名，减少依赖。

scrollView.vue　

<script>
import {
  addResizeListener,
  removeResizeListener
} from 'element-ui/src/utils/resize-event'


export default {
  props: {
    width: {
      type: String,
      default: '100%'
    }
  },




  data () {
    return {
      scrollable: false,
      navOffset: 0
    }
  },




  computed: {
    navStyle () {
      return {
        transform: `translateX(-${this.navOffset}px)`
      }
    }
  },




  methods: {
    scrollPrev () {
      const containerSize = this.$refs.navScroll.offsetWidth
      const currentOffset = this.navOffset




      if (!currentOffset) return




      const newOffset =
        currentOffset > containerSize ? currentOffset - containerSize : 0




      this.navOffset = newOffset
    },
    scrollNext () {
      const navSize = this.$refs.nav.offsetWidth
      const containerSize = this.$refs.navScroll.offsetWidth
      const currentOffset = this.navOffset




      if (navSize - currentOffset <= containerSize) return




      const newOffset =
        navSize - currentOffset > containerSize * 2
          ? currentOffset + containerSize
          : navSize - containerSize




      this.navOffset = newOffset
    },
    scrollToActiveTab () {
      if (!this.scrollable) return




      const nav = this.$refs.nav
      const activeTab = this.$el.querySelector('.is-active')
      if (!activeTab) return
      const navScroll = this.$refs.navScroll
      const activeTabBounding = activeTab.getBoundingClientRect()
      const navScrollBounding = navScroll.getBoundingClientRect()
      const maxOffset = nav.offsetWidth - navScrollBounding.width
      const currentOffset = this.navOffset
      let newOffset = currentOffset




      if (activeTabBounding.left < navScrollBounding.left) {
        newOffset =
          currentOffset - (navScrollBounding.left - activeTabBounding.left)
      }
      if (activeTabBounding.right > navScrollBounding.right) {
        newOffset =
          currentOffset + activeTabBounding.right - navScrollBounding.right
      }
      newOffset = Math.max(newOffset, 0)
      this.navOffset = Math.min(newOffset, maxOffset)
    },
    update () {
      if (!this.$refs.nav) return
      const navSize = this.$refs.nav.offsetWidth
      this.height = this.$refs.nav.offsetHeight
      const containerSize = this.$refs.navScroll.offsetWidth
      const currentOffset = this.navOffset
      if (containerSize < navSize) {
        const currentOffset = this.navOffset
        this.scrollable = this.scrollable || {}
        this.scrollable.prev = currentOffset
        this.scrollable.next = currentOffset + containerSize < navSize
        if (navSize - currentOffset < containerSize) {
          this.navOffset = navSize - containerSize
        }
      } else {
        this.scrollable = false
        if (currentOffset > 0) {
          this.navOffset = 0
        }
      }
    }
  },




  updated () {
    this.update()
  },




  render () {
    const { navStyle, scrollable, scrollNext, scrollPrev, height, width } = this
    const lineHeight = {
      'line-height': height + 'px'
    }
    const scrollBtn = scrollable
      ? [
        <span
          class={['scrollView__nav-prev', scrollable.prev ? '' : 'is-disabled']}
          on-click={scrollPrev}
        >
          <i
            style={lineHeight}
            class="el-icon-arrow-left"></i>
        </span>,
        <span
          class={['scrollView__nav-next', scrollable.next ? '' : 'is-disabled']}
          on-click={scrollNext}
        >
          <i style={lineHeight}
            class="el-icon-arrow-right"></i>
        </span>
      ]
      : null




    return (
      <div
        class={[
          'scrollView__nav-wrap',
          scrollable ? 'is-scrollable' : ''
        ]}
        style={{ width }}
      >
        {scrollBtn}
        <div
          class="scrollView__nav-scroll"
          ref="navScroll"
        >
          <div
            class="scrollView__nav"
            ref="nav"
            style={navStyle}
          >
            {this.$slots.default}
          </div>
        </div>
      </div>
    )
  },




  mounted () {
    addResizeListener(this.$el, this.update)
  },




  beforeDestroy () {
    if (this.$el && this.update) removeResizeListener(this.$el, this.update)
  }
}
</script>




<style lang="less">
.scrollView__nav-wrap {
  display: inline-block;
  overflow: hidden;
  margin-bottom: -1px;
  position: relative;
  vertical-align: middle;
}




.scrollView__nav-wrap.is-scrollable {
  padding: 0 20px;
  -webkit-box-sizing: border-box;
  box-sizing: border-box;
}




.scrollView__nav-wrap::after {
  display: none;
}




.scrollView__nav-scroll {
  overflow: hidden;
}




.scrollView__nav {
  white-space: nowrap;
  position: relative;
  transition: transform 0.3s, -webkit-transform 0.3s;
  float: left;
  z-index: 2;
}




.scrollView__nav-prev {
  left: 0;
}
.scrollView__nav-next {
  right: 0;
}
.scrollView__nav-next,
.scrollView__nav-prev {
  position: absolute;
  cursor: pointer;
  line-height: 44px;
  font-size: 12px;
  color: #909399;
}
</style>