el-scrollbar 使用說明

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---

el-scrollbar

element-ui 的滾動條組件 ，官方文檔上面是沒有介紹這個組件的。

效果圖：

簡單使用： 

<template>
  <div style="height:768px;">
    <el-scrollbar style="height:100%">
      <ul>
        <li style="height: 300px;" />
        <li style="height: 300px;" />
        <li style="height: 300px;" />
        <li style="height: 300px;" />
      </ul>
    </el-scrollbar>
  </div>
</template>

注意：

1. 在使用時要必須設置外層容器高度。

2. 並且要設置el-scrollbar 的高度爲100%。將需要滑動的 html 代碼包裹起來。

如果需要去掉水平滾動條，需要添加下面樣式：

.el-scrollbar__wrap{
  overflow-x: hidden;
}

---

 進階使用：

使用 el-scrollbar 包裹 router-view 時，router-view 顯示 的路由發生改變時，滾動條不會復位到頁面的頂部。查看 el-scrollbar 組件的源碼，得到最佳解決方案如下。el-scrollbar 源碼在頁面底部，有興趣的可以看看。如有問題，歡迎評論！

最佳解決方案：

<template>
  <div>
    <el-menu :default-active="activeIndex" :router="true" class="el-menu-demo" mode="horizontal">
      <el-menu-item index="/processingCenter">處理中心</el-menu-item>
      <el-submenu index="/workbench">
        <template slot="title">我的工作臺</template>
        <el-menu-item index="/workbench/option1">選項1</el-menu-item>
        <el-menu-item index="/workbench/option2">選項2</el-menu-item>
        <el-submenu index="/workbench/option3">
          <template slot="title">選項3</template>
          <el-menu-item index="/workbench/option3/option1">選項1</el-menu-item>
          <el-menu-item index="/workbench/option3/option2">選項2</el-menu-item>
        </el-submenu>
      </el-submenu>
      <el-menu-item index="/messageCenter" disabled>消息中心</el-menu-item>
    </el-menu>

    <div style="height: 500px;">
      <el-scrollbar ref="scrollbar" style="height: 100%">
        <router-view />
      </el-scrollbar>
    </div>
  </div>
</template>

<script>
export default {
  name: 'ScrollRouterView',
  data() {
    return {
      activeIndex: '1'
    }
  },
  watch: {
    // 檢測 當前路由地址的變化, 路由地址發生改變時, router-view 顯示的路由改變時需要將滾動條復位到頂部
    '$route.path'(newValue, oldValue) {
      console.log(oldValue, typeof oldValue, '$route.path oldValue')
      console.log(newValue, typeof newValue, '$route.path newValue')
      // 通過 ref 拿到 el-scrollbar 的實例對象( vue 實例對象)
      const scrollbar = this.$refs.scrollbar
      // scrollbar 的實例對象相當於在 el-scrollbar 組件裏面的 this
      const wrap = scrollbar.$refs.wrap
      // $refs.wrap 是 el-scrollbar 組件裏的 ref='wrap', 是一個 dom
      wrap.scrollTo(0, 0)
    }
  },
  created() {
  },
  methods: {
  }
}
</script>

<style lang="scss">
.el-scrollbar__wrap{
  overflow-x: hidden;
}
</style>

 

---

組件源碼： 

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/***/ 122:
/***/ (function(module, __webpack_exports__, __webpack_require__) {

"use strict";
__webpack_require__.r(__webpack_exports__);

// EXTERNAL MODULE: external "element-ui/lib/utils/resize-event"
var resize_event_ = __webpack_require__(15);

// EXTERNAL MODULE: external "element-ui/lib/utils/scrollbar-width"
var scrollbar_width_ = __webpack_require__(37);
var scrollbar_width_default = /*#__PURE__*/__webpack_require__.n(scrollbar_width_);

// EXTERNAL MODULE: external "element-ui/lib/utils/util"
var util_ = __webpack_require__(3);

// EXTERNAL MODULE: external "element-ui/lib/utils/dom"
var dom_ = __webpack_require__(2);

// CONCATENATED MODULE: ./packages/scrollbar/src/util.js
var BAR_MAP = {
  vertical: {
    offset: 'offsetHeight',
    scroll: 'scrollTop',
    scrollSize: 'scrollHeight',
    size: 'height',
    key: 'vertical',
    axis: 'Y',
    client: 'clientY',
    direction: 'top'
  },
  horizontal: {
    offset: 'offsetWidth',
    scroll: 'scrollLeft',
    scrollSize: 'scrollWidth',
    size: 'width',
    key: 'horizontal',
    axis: 'X',
    client: 'clientX',
    direction: 'left'
  }
};

function renderThumbStyle(_ref) {
  var move = _ref.move,
      size = _ref.size,
      bar = _ref.bar;

  var style = {};
  var translate = 'translate' + bar.axis + '(' + move + '%)';

  style[bar.size] = size;
  style.transform = translate;
  style.msTransform = translate;
  style.webkitTransform = translate;

  return style;
};
// CONCATENATED MODULE: ./packages/scrollbar/src/bar.js



/* istanbul ignore next */
/* harmony default export */ var src_bar = ({
  name: 'Bar',

  props: {
    vertical: Boolean,
    size: String,
    move: Number
  },

  computed: {
    bar: function bar() {
      return BAR_MAP[this.vertical ? 'vertical' : 'horizontal'];
    },
    wrap: function wrap() {
      return this.$parent.wrap;
    }
  },

  render: function render(h) {
    var size = this.size,
        move = this.move,
        bar = this.bar;


    return h(
      'div',
      {
        'class': ['el-scrollbar__bar', 'is-' + bar.key],
        on: {
          'mousedown': this.clickTrackHandler
        }
      },
      [h('div', {
        ref: 'thumb',
        'class': 'el-scrollbar__thumb',
        on: {
          'mousedown': this.clickThumbHandler
        },

        style: renderThumbStyle({ size: size, move: move, bar: bar }) })]
    );
  },


  methods: {
    clickThumbHandler: function clickThumbHandler(e) {
      // prevent click event of right button
      if (e.ctrlKey || e.button === 2) {
        return;
      }
      this.startDrag(e);
      this[this.bar.axis] = e.currentTarget[this.bar.offset] - (e[this.bar.client] - e.currentTarget.getBoundingClientRect()[this.bar.direction]);
    },
    clickTrackHandler: function clickTrackHandler(e) {
      var offset = Math.abs(e.target.getBoundingClientRect()[this.bar.direction] - e[this.bar.client]);
      var thumbHalf = this.$refs.thumb[this.bar.offset] / 2;
      var thumbPositionPercentage = (offset - thumbHalf) * 100 / this.$el[this.bar.offset];

      this.wrap[this.bar.scroll] = thumbPositionPercentage * this.wrap[this.bar.scrollSize] / 100;
    },
    startDrag: function startDrag(e) {
      e.stopImmediatePropagation();
      this.cursorDown = true;

      Object(dom_["on"])(document, 'mousemove', this.mouseMoveDocumentHandler);
      Object(dom_["on"])(document, 'mouseup', this.mouseUpDocumentHandler);
      document.onselectstart = function () {
        return false;
      };
    },
    mouseMoveDocumentHandler: function mouseMoveDocumentHandler(e) {
      if (this.cursorDown === false) return;
      var prevPage = this[this.bar.axis];

      if (!prevPage) return;

      var offset = (this.$el.getBoundingClientRect()[this.bar.direction] - e[this.bar.client]) * -1;
      var thumbClickPosition = this.$refs.thumb[this.bar.offset] - prevPage;
      var thumbPositionPercentage = (offset - thumbClickPosition) * 100 / this.$el[this.bar.offset];

      this.wrap[this.bar.scroll] = thumbPositionPercentage * this.wrap[this.bar.scrollSize] / 100;
    },
    mouseUpDocumentHandler: function mouseUpDocumentHandler(e) {
      this.cursorDown = false;
      this[this.bar.axis] = 0;
      Object(dom_["off"])(document, 'mousemove', this.mouseMoveDocumentHandler);
      document.onselectstart = null;
    }
  },

  destroyed: function destroyed() {
    Object(dom_["off"])(document, 'mouseup', this.mouseUpDocumentHandler);
  }
});
// CONCATENATED MODULE: ./packages/scrollbar/src/main.js
// reference https://github.com/noeldelgado/gemini-scrollbar/blob/master/index.js






/* istanbul ignore next */
/* harmony default export */ var main = ({
  name: 'ElScrollbar',

  components: { Bar: src_bar },

  props: {
    native: Boolean,
    wrapStyle: {},
    wrapClass: {},
    viewClass: {},
    viewStyle: {},
    noresize: Boolean, // 如果 container 尺寸不會發生變化，最好設置它可以優化性能
    tag: {
      type: String,
      default: 'div'
    }
  },

  data: function data() {
    return {
      sizeWidth: '0',
      sizeHeight: '0',
      moveX: 0,
      moveY: 0
    };
  },


  computed: {
    wrap: function wrap() {
      return this.$refs.wrap;
    }
  },

  render: function render(h) {
    var gutter = scrollbar_width_default()();
    var style = this.wrapStyle;

    if (gutter) {
      var gutterWith = '-' + gutter + 'px';
      var gutterStyle = 'margin-bottom: ' + gutterWith + '; margin-right: ' + gutterWith + ';';

      if (Array.isArray(this.wrapStyle)) {
        style = Object(util_["toObject"])(this.wrapStyle);
        style.marginRight = style.marginBottom = gutterWith;
      } else if (typeof this.wrapStyle === 'string') {
        style += gutterStyle;
      } else {
        style = gutterStyle;
      }
    }
    var view = h(this.tag, {
      class: ['el-scrollbar__view', this.viewClass],
      style: this.viewStyle,
      ref: 'resize'
    }, this.$slots.default);
    var wrap = h(
      'div',
      {
        ref: 'wrap',
        style: style,
        on: {
          'scroll': this.handleScroll
        },

        'class': [this.wrapClass, 'el-scrollbar__wrap', gutter ? '' : 'el-scrollbar__wrap--hidden-default'] },
      [[view]]
    );
    var nodes = void 0;

    if (!this.native) {
      nodes = [wrap, h(src_bar, {
        attrs: {
          move: this.moveX,
          size: this.sizeWidth }
      }), h(src_bar, {
        attrs: {
          vertical: true,
          move: this.moveY,
          size: this.sizeHeight }
      })];
    } else {
      nodes = [h(
        'div',
        {
          ref: 'wrap',
          'class': [this.wrapClass, 'el-scrollbar__wrap'],
          style: style },
        [[view]]
      )];
    }
    return h('div', { class: 'el-scrollbar' }, nodes);
  },


  methods: {
    handleScroll: function handleScroll() {
      var wrap = this.wrap;

      this.moveY = wrap.scrollTop * 100 / wrap.clientHeight;
      this.moveX = wrap.scrollLeft * 100 / wrap.clientWidth;
    },
    update: function update() {
      var heightPercentage = void 0,
          widthPercentage = void 0;
      var wrap = this.wrap;
      if (!wrap) return;

      heightPercentage = wrap.clientHeight * 100 / wrap.scrollHeight;
      widthPercentage = wrap.clientWidth * 100 / wrap.scrollWidth;

      this.sizeHeight = heightPercentage < 100 ? heightPercentage + '%' : '';
      this.sizeWidth = widthPercentage < 100 ? widthPercentage + '%' : '';
    }
  },

  mounted: function mounted() {
    if (this.native) return;
    this.$nextTick(this.update);
    !this.noresize && Object(resize_event_["addResizeListener"])(this.$refs.resize, this.update);
  },
  beforeDestroy: function beforeDestroy() {
    if (this.native) return;
    !this.noresize && Object(resize_event_["removeResizeListener"])(this.$refs.resize, this.update);
  }
});
// CONCATENATED MODULE: ./packages/scrollbar/index.js


/* istanbul ignore next */
main.install = function (Vue) {
  Vue.component(main.name, main);
};

/* harmony default export */ var scrollbar = __webpack_exports__["default"] = (main);

/***/ }),

/***/ 15:
/***/ (function(module, exports) {

module.exports = require("element-ui/lib/utils/resize-event");

/***/ }),

/***/ 2:
/***/ (function(module, exports) {

module.exports = require("element-ui/lib/utils/dom");

/***/ }),

/***/ 3:
/***/ (function(module, exports) {

module.exports = require("element-ui/lib/utils/util");

/***/ }),

/***/ 37:
/***/ (function(module, exports) {

module.exports = require("element-ui/lib/utils/scrollbar-width");

/***/ })

/******/ });