element-ui Collapse 折叠面板源码分析整理笔记（十）

Collapse 折叠面板源码：

collapse.vue

<template>
    <!--一组折叠面板最外层包裹div-->
  <div class="el-collapse" role="tablist" aria-multiselectable="true">
    <slot></slot>
  </div>
</template>
<script>
  export default {
    name: 'ElCollapse',

    componentName: 'ElCollapse',

    props: {
      accordion: Boolean, //是否手风琴模式
      value: {  //当前激活的面板(如果是手风琴模式，绑定值类型需要为string，否则为array)
        type: [Array, String, Number],
        default() {
          return [];
        }
      }
    },

    data() {
      return {
        activeNames: [].concat(this.value) //当前激活的面板名称数组
      };
    },

    provide() {
      return {
        collapse: this
      };
    },

    watch: {
      value(value) {
        this.activeNames = [].concat(value);
      }
    },

    methods: {
      setActiveNames(activeNames) {
        // 返回activeNames数组的副本
        activeNames = [].concat(activeNames);
        //如果是手风琴模式返回activeNames[0]，不是则返回整个数组
        let value = this.accordion ? activeNames[0] : activeNames;
        this.activeNames = activeNames;
        //触发父组件的input方法
        this.$emit('input', value);
        //触发父组件的change方法
        this.$emit('change', value);
      },
      handleItemClick(item) {
        // 如果是手风琴模式
        if (this.accordion) {
          this.setActiveNames(
            (this.activeNames[0] || this.activeNames[0] === 0) &&
            this.activeNames[0] === item.name
              ? '' : item.name
          );
        } else { //如果不是手风琴模式
          let activeNames = this.activeNames.slice(0);
          let index = activeNames.indexOf(item.name);
          if (index > -1) { //如果该面板已经是激活状态，就将其从activeNames数组中删除
            activeNames.splice(index, 1);
          } else {  //如果该面板还未是激活状态，就将其push进activeNames数组中
            activeNames.push(item.name);
          }
          this.setActiveNames(activeNames);
        }
      }
    },

    created() {
      this.$on('item-click', this.handleItemClick);
    }
  };
</script>

collapse-item.vue

<template>
    <!--每个折叠面板最外层包裹div-->
  <div class="el-collapse-item" :class="{'is-active': isActive}">

    <div role="tab" :aria-expanded="isActive" :aria-controls="`el-collapse-content-${id}`" :aria-describedby ="`el-collapse-content-${id}`">
        <!--面板头部，包含面板标题和箭头图标-->
        <div class="el-collapse-item__header"
        @click="handleHeaderClick"
        role="button"
        :id="`el-collapse-head-${id}`"
        tabindex="0"
        @keyup.space.enter.stop="handleEnterClick"
        :class="{
          'focusing': focusing,
          'is-active': isActive
        }"
        @focus="handleFocus"
        @blur="focusing = false"
      >
         <!--折叠面板的标题-->
        <slot name="title">{{title}}</slot>
         <!--折叠面板的收起或折叠的箭头图标-->
        <i class="el-collapse-item__arrow el-icon-arrow-right" :class="{'is-active': isActive}"></i>
      </div>
    </div>
    <!--折叠面板内容区域 el-collapse-transition组件主要是为了添加内容显示隐藏时的动画效果-->
    <el-collapse-transition>
      <div class="el-collapse-item__wrap" v-show="isActive"
        role="tabpanel"
        :aria-hidden="!isActive"
        :aria-labelledby="`el-collapse-head-${id}`"
        :id="`el-collapse-content-${id}`"
      >
        <div class="el-collapse-item__content">
          <slot></slot>
        </div>
      </div>
    </el-collapse-transition>
  </div>
</template>
<script>
  import ElCollapseTransition from 'element-ui/src/transitions/collapse-transition';
  import Emitter from 'element-ui/src/mixins/emitter';
  import { generateId } from 'element-ui/src/utils/util';

  export default {
    name: 'ElCollapseItem',

    componentName: 'ElCollapseItem',

    mixins: [Emitter],

    components: { ElCollapseTransition },

    data() {
      return {
        contentWrapStyle: {
          height: 'auto',
          display: 'block'
        },
        contentHeight: 0,
        focusing: false,
        isClick: false
      };
    },

    inject: ['collapse'],

    props: {
      title: String,
      name: {
        type: [String, Number],
        default() {
          return this._uid;
        }
      }
    },

    computed: {
      // 返回当前面板是否被激活
      isActive() {
        // 判断当前面板的名称是否在activeNames中
        return this.collapse.activeNames.indexOf(this.name) > -1;
      },
      id() {
        // 返回随机数id
        return generateId();
      }
    },

    methods: {
      handleFocus() {
        setTimeout(() => {
          if (!this.isClick) {
            this.focusing = true;
          } else {
            this.isClick = false;
          }
        }, 50);
      },
      handleHeaderClick() {
        // 触发父组件的item-click事件
        this.dispatch('ElCollapse', 'item-click', this);
        this.focusing = false;
        this.isClick = true;
      },
      handleEnterClick() {
        this.dispatch('ElCollapse', 'item-click', this);
      }
    }
  };
</script>