vue 实现顶部元素浮动

<template>
  <div :style="{height:height+'px',zIndex:zIndex}">
    <div
      :class="className"
      :style="{top:(isSticky ? stickyTop +'px' : ''),zIndex:zIndex,position:position,width:width,height:height+'px'}"
    >
      <slot>
        <div>sticky</div>
      </slot>
    </div>
  </div>
</template>

<script>
export default {
  name: 'Sticky',
  props: {
    stickyTop: {
      type: Number,
      default: 0
    },
    zIndex: {
      type: Number,
      default: 1
    },
    className: {
      type: String,
      default: ''
    }
  },
  data() {
    return {
      active: false,
      position: '',
      width: undefined,
      height: undefined,
      isSticky: false
    }
  },
  mounted() {
    this.height = this.$el.getBoundingClientRect().height
    window.addEventListener('scroll', this.handleScroll)
    window.addEventListener('resize', this.handleResize)
  },
  activated() {
    this.handleScroll()
  },
  destroyed() {
    window.removeEventListener('scroll', this.handleScroll)
    window.removeEventListener('resize', this.handleResize)
  },
  methods: {
    sticky() {
      if (this.active) {
        return
      }
      this.position = 'fixed'
      this.active = true
      this.width = this.width + 'px'
      this.isSticky = true
    },
    handleReset() {
      if (!this.active) {
        return
      }
      this.reset()
    },
    reset() {
      this.position = ''
      this.width = 'auto'
      this.active = false
      this.isSticky = false
    },
    handleScroll() {
      const width = this.$el.getBoundingClientRect().width
      this.width = width || 'auto'
      const offsetTop = this.$el.getBoundingClientRect().top
      if (offsetTop < this.stickyTop) {
        this.sticky()
        return
      }
      this.handleReset()
    },
    handleResize() {
      if (this.isSticky) {
        this.width = this.$el.getBoundingClientRect().width + 'px'
      }
    }
  }
}
</script>

<template>
  <div>
    <sticky :z-index="10" class-name="sub-navbar">
      <el-dropdown trigger="click">
        <el-button plain>
          Platform<i class="el-icon-caret-bottom el-icon--right" />
        </el-button>
        <el-dropdown-menu slot="dropdown" class="no-border">
          <el-checkbox-group v-model="platforms" style="padding: 5px 15px;">
            <el-checkbox v-for="item in platformsOptions" :key="item.key" :label="item.key">
              {{ item.name }}
            </el-checkbox>
          </el-checkbox-group>
        </el-dropdown-menu>
      </el-dropdown>

      <el-dropdown trigger="click">
        <el-button plain>
          Link<i class="el-icon-caret-bottom el-icon--right" />
        </el-button>
        <el-dropdown-menu slot="dropdown" class="no-padding no-border" style="width:300px">
          <el-input v-model="url" placeholder="Please enter the content">
            <template slot="prepend">
              Url
            </template>
          </el-input>
        </el-dropdown-menu>
      </el-dropdown>

      <div class="time-container">
        <el-date-picker v-model="time" type="datetime" format="yyyy-MM-dd HH:mm:ss" placeholder="Release time" />
      </div>

      <el-button style="margin-left: 10px;" type="success">
        publish
      </el-button>
    </sticky>

    <div class="components-container">
      <aside>Sticky header, {{ $t('components.stickyTips') }}</aside>
      <div>placeholder</div>
      <div>placeholder</div>
      <div>placeholder</div>
      <div>placeholder</div>
      <div>placeholder</div>
      <div>placeholder</div>
      <div>placeholder</div>
      <div>placeholder</div>
      <div>placeholder</div>
      <div>placeholder</div>
      <div>placeholder</div>
      <div>placeholder</div>
      <div>placeholder</div>
      <sticky :sticky-top="200">
        <el-button type="primary"> placeholder</el-button>
      </sticky>
      <div>placeholder</div>
      <div>placeholder</div>
      <div>placeholder</div>
      <div>placeholder</div>
      <div>placeholder</div>
      <div>placeholder</div>
      <div>placeholder</div>
      <div>placeholder</div>
      <div>placeholder</div>
      <div>placeholder</div>
      <div>placeholder</div>
      <div>placeholder</div>
      <div>placeholder</div>
      <div>placeholder</div>
      <div>placeholder</div>
      <div>placeholder</div>
      <div>placeholder</div>
      <div>placeholder</div>
      <div>placeholder</div>
      <div>placeholder</div>
      <div>placeholder</div>
      <div>placeholder</div>
      <div>placeholder</div>
      <div>placeholder</div>
      <div>placeholder</div>
      <div>placeholder</div>
      <div>placeholder</div>
      <div>placeholder</div>
      <div>placeholder</div>
      <div>placeholder</div>
      <div>placeholder</div>
      <div>placeholder</div>
      <div>placeholder</div>
      <div>placeholder</div>
      <div>placeholder</div>
      <div>placeholder</div>
      <div>placeholder</div>
      <div>placeholder</div>
    </div>
  </div>
</template>

<script>
import Sticky from '@/components/Sticky'

export default {
  name: 'StickyDemo',
  components: { Sticky },
  data() {
    return {
      time: '',
      url: '',
      platforms: ['a-platform'],
      platformsOptions: [
        { key: 'a-platform', name: 'platformA' },
        { key: 'b-platform', name: 'platformB' },
        { key: 'c-platform', name: 'platformC' }
      ],
      pickerOptions: {
        disabledDate(time) {
          return time.getTime() > Date.now()
        }
      }
    }
  }
}
</script>

<style scoped>
.components-container div {
  margin: 10px;
}

.time-container {
  display: inline-block;
}
</style>