el-dropdown 两个以上el-dropdown互相切换时，第一次active只切换，不展示下拉框，第二次再点击，才展示下拉框

1.可以在el-dropdown上设置蒙层使第一次点击时，点击触发在蒙层上，不触发el-dropdown点击事件。

<template>
    <div id="test">
        <div class="train-tab__item"  @click="tabFeatureList(0)" style="min-width: 135px;height: 40px;float: left">
            <el-dropdown style="cursor: pointer; outline: none;margin-left: -15px;height: 40px;line-height: 40px;"  @command="getList" trigger="click">
                <div id="list">
                    <span class="el-dropdown-link">
                        我是tab1
                    </span>
                </div>

                <el-dropdown-menu slot="dropdown" class="pro-dropdown-menu">
                    <el-dropdown-item
                        v-for="(item, index) in featureList"
                        :divided="index==1"
                        :command="item"
                        :key="item.name + index">
                        {{ item.name }}
                    </el-dropdown-item>
                </el-dropdown-menu>
            </el-dropdown>
            <div style="top: 0; left: -20px;position: absolute; height: 40px; opacity: 0;" v-if="activeIndex != 0">
                <span style="margin-left: 20px; margin-right: 90px;">{{ curFeatureObj.name }}</span>
            </div>
        </div>
        <div class="train-tab__item" :class="{'train-tab__actived': activeIndex == 1}" @click="tabOriginData(1)">
            <span>
                <img src="../../images/origin-dataset.png" class="origin-data-pic">
                <span>我是tab2</span>
            </span>
        </div>
    </div>
</template>
<script>
    export default {
        data () {

        },
        methods: {
            tabFeatureList (tag) {
                this.activeIndex = tag;
            },
            tabOriginData (tag) {
                this.activeIndex = tag;
            },
        }
    }
</script>

2.第二种方式

利用点击时activeIndex更换时dom渲染的规律及顺序，使第一次点击时不展示下拉（由于activeIndex切换，会把原来的那个dom删掉，这个过程中没有来得及显示之前的点击）,这个方式不是很稳妥，第一种方式相对好一些

<template>
    <div id="test">
        <div class="train-tab__item"  @click="tabFeatureList(0)" v-if="activeIndex != 0" style="min-width: 135px;height: 40px;float: left">
                <el-dropdown style="cursor: pointer; outline: none;margin-left: -15px;height: 40px;line-height: 40px;"  @command="getList" trigger="click">
                    <div id="list">
                        <span class="el-dropdown-link">
                            我是tab1
                        </span>
                    </div>

                    <el-dropdown-menu slot="dropdown" class="pro-dropdown-menu">
                        <el-dropdown-item
                            v-for="(item, index) in featureList"
                            :divided="index==1"
                            :command="item"
                            :key="item.name + index">
                            {{ item.name }}
                        </el-dropdown-item>
                    </el-dropdown-menu>
                </el-dropdown>
        </div>
        <div class="train-tab__item"  @click="tabFeatureList(0)" v-else style="min-width: 135px;height: 40px;float: left">
                <el-dropdown style="cursor: pointer; outline: none;margin-left: -15px;height: 40px;line-height: 40px;"  @command="getList" trigger="click">
                    <div id="list1">
                        <span class="el-dropdown-link">
                            我是tab1
                        </span>
                    </div>

                    <el-dropdown-menu slot="dropdown" class="pro-dropdown-menu">
                        <el-dropdown-item
                                v-for="(item, index) in featureList"
                                :divided="index==1"
                                :command="item"
                                :key="item.name + index">
                            {{ item.name }}
                        </el-dropdown-item>
                    </el-dropdown-menu>
                </el-dropdown>
        </div>
        <div class="train-tab__item" :class="{'train-tab__actived': activeIndex == 1}" @click="tabOriginData(1)">
            <span>
                <img src="../../images/origin-dataset.png" class="origin-data-pic">
                <span>我是tab2</span>
            </span>
        </div>
    </div>
</template>
<script>
    export default {
        data () {

        },
        methods: {
            tabFeatureList (tag) {
                this.activeIndex = tag;
            },
            tabOriginData (tag) {
                this.activeIndex = tag;
            },
        }
    }
</script>