react实现移动端下拉菜单的示例代码

前言

项目中要实现类似与vant的dropdownmenu:下拉菜单。看了vans 的效果 其实也没什么难度，于是动手鲁了一个这样的组件。
项目的技术栈为react全家桶+material ui + ant design mobile。

vans的效果

我自己实现的效果

思路

常规做法获取dom元素，动态修改选中dom的innerhtml。
当然这种方式不是react推荐的

我的做法既然react不推荐直接操作dom元素，那可以采用动态动态修改class的方式达到效果，例如：

let cls ="normal"
div未被选中时
<div classname={cls}/> 
div被选中时
cls+=" current"
<div classname ={cls}>

实现步骤

顶部tab采用三个div的方式布局，由于需要动态修改tab上的标题，所以定义一个数组，reducer中的tab数据结构如下

let tabs = {};
tabs[tabkay.area] = {
key: tabkay.area,
text: "全部区域",
obj: {}
};
tabs[tabkay.sort] = {
key: tabkay.sort,
text: "综合排序",
obj: {}
};
tabs[tabkay.filter] = {
key: tabkay.filter,
text: "筛选",
obj: sx
};
const initialstate = {
areas: [{ id: "", name: "全部区域" }],
tabs: tabs,
actionkey: tabkay.area,// 标识了当前选中tab
closepanel: true // 标识panel div 是否显示
};

tabui组件的页面容器渲染方法

rendertabs() {
const { tabs, actionkey, closepanel } = this.props;
//---------
if (!closepanel) {
 fixedbody();
} else {
 loosebody();
}
//---------

let aray = [];
for (let key in tabs) {
 let item = tabs[key];
 let cls = item.key + " item";
 if (item.key === actionkey && !closepanel) {
  cls += " current";
 }

 aray.push(
  <div classname={cls} key={item.key} onclick={() => this.onchangetab(item.key)}>
   {item.text}
  </div>);
}

return aray;
}

样式：这里边有个技巧，就是利用了css元素选择器的伪类的方式巧妙实现了箭头以及箭头的旋转动画

.item {
flex: 1;
font-size: 15px;
border-right: 0.5px solid #eaeaea;
text-align: center;

&:last-child {
 border: none;
}

&.area:after, &.sort:after, &.filter:after {
 content: "";
 display: inline-block;
 width: 5px;
 height: 5px;
 margin-bottom: 2px;
 margin-left: 6px;
 border: 2px solid #666;
 border-width: 0 2px 2px 0;
 transform: rotate(45deg);
 -webkit-transform: rotate(45deg);
 -webkit-transition: .3s;
 transition: .3s;
}

&.current {
 color: #0084ff;
}

&.current:after {
 border-color: #0084ff;
 transform: rotate(225deg);
 -webkit-transform: rotate(225deg);
}

chrome 查看元素

全部区域tab被选中：

综合tab被选中

每次点击不同的tab时 都会自动的渲染current这个css样式，这样就实现了下拉菜单的功能。

完整代码

/**
 * class:
 * author: miyaliunian
 * date: 2019/5/26
 * description: tabs 选择器
 * 医院列表
 */
import react, { component } from "react";
import { zhpx, tabkay } from "@api/constant";
//util
import { fixedbody, loosebody } from "@utils/fixrollingpenetration";
//redux
import { connect } from "react-redux";
import { bindactioncreators } from "redux";
import { actions as tabactions, gettabs, getareaslist, getactionkey, getclosepanel } from "@reduxs/modules/tabs";
import { actions as hospitalactions,} from "@reduxs/modules/hospital";

//样式
import "./tabs.less";

class tabs extends component {
 
 /**
  * 变化当前点击的item状态 同时filter 请求
  * @param filteritem 当前选中的元素
  * @param key  哪个tab是选中状态
  */
 changedofilter(filteritem, key, event) {
  const { tabactions: { changefilter }, hospitalactions:{filterhosicontentlist} } = this.props;
  event.stoppropagation();
  changefilter(filteritem, key, (filter) => {
   filterhosicontentlist(filter);
  });
 }

 /**
  * 筛选tab确定按钮
  * @param event
  */
 filterpanel(event) {
  const {tabactions:{closepanelaction}, tabs,hospitalactions:{filterhosicontentlist}} = this.props;
  event.stoppropagation();
  closepanelaction(()=>{
   filterhosicontentlist(tabs)
  })
 }

 /**
  * 点击切换tab
  * @param key
  */
 onchangetab(key) {
  const { actionkey,tabactions: { changetab } } = this.props;
  let closepanel = false;
  //如果前后点击的是同一个tab 就关闭panel
  if (actionkey === key && !this.props.closepanel) {
   closepanel = true;
  }
  closepanel ? loosebody() : fixedbody();
  changetab(key, closepanel);
 }

 /**
  * 渲染顶部tab
  */
 rendertabs() {
  const { tabs, actionkey, closepanel } = this.props;
  //---------
  if (!closepanel) {
   fixedbody();
  } else {
   loosebody();
  }
  //---------

  let aray = [];
  for (let key in tabs) {
   let item = tabs[key];
   let cls = item.key + " item";
   if (item.key === actionkey && !closepanel) {
    cls += " current";
   }

   aray.push(
    <div classname={cls} key={item.key} onclick={() => this.onchangetab(item.key)}>
     {item.text}
    </div>);
  }

  return aray;
 }

 /**
  * 全部区域
  * @returns {*}
  */
 renderareacontent() {
  const { areaslist } = this.props;
  return areaslist.map((item, index) => {
   let cls = item.active + " area-item";
   return (
    <li key={index} classname={"area-item"} onclick={(e) => this.changedofilter(item, tabkay.area, e)}>
     {item.name}
    </li>
   );
  });
 }


 /**
  * 全部排序
  * @returns {any[]}
  */
 rendersortcontent() {
  let sortlist = zhpx;
  return sortlist.map((item, index) => {
   let cls = item.action ? "type-item active" : "type-item";

   return (
    <li key={index} classname={cls} onclick={(e) => this.changedofilter(item, tabkay.sort, e)}>
     {item.name}
    </li>
   );
  });
 }


 /**
  * 筛选
  * @returns {*}
  */

 renderfilterinnercontent(items/*filterlist*/) {
  return items.map((item, index) => {
   let cls = "cate-box";
   if (item.active) {
    cls += " active";
   }

   return (
    <div key={index} classname={cls} onclick={(e) => this.changedofilter(item, tabkay.filter, e)}>
     {item.name}
    </div>
   );
  });

 }

 renderfiltercontent() {
  let filterlist = [];
  const { tabs } = this.props;
  filterlist = tabs[tabkay.filter].obj;
  return filterlist.map((item, index) => {
   return (
    <li key={index} classname={"filter-item"}>
     <p classname={"filter-title"}>{index == 0 ? `医院类型: ${item.grouptitle}` : `医院等级: ${item.grouptitle}`}</p>
     <div classname={"item-content"}>
      {this.renderfilterinnercontent(item.items, filterlist)}
     </div>
    </li>
   );
  });
 }

 /**
  * 渲染过滤面板
  */
 rendercontent() {
  const { tabs, actionkey } = this.props;
  let array = [];
  for (let key in tabs) {
   let item = tabs[key];
   let cls = item.key + "-panel";
   if (item.key === actionkey) {
    cls += " current";
   }

   // 全部区域
   if (item.key === tabkay.area) {
    array.push(
     <ul key={item.key} classname={cls}>
      {this.renderareacontent()}
     </ul>
    );
   } else if (item.key === tabkay.sort) {
    // 综合排序
    array.push(
     <ul key={item.key} classname={cls}>
      {this.rendersortcontent()}
     </ul>
    );
   } else if (item.key === tabkay.filter) {
    // 筛选
    array.push(
     <ul key={item.key} classname={cls}>
      {this.renderfiltercontent()}
      <div classname={"filterbtn"} onclick={(e) => this.filterpanel(e)}>
       确定
      </div>
     </ul>
    );
   }

  }
  return array;
 }


 render() {
  const { closepanel, tabactions: { closepanelaction } } = this.props;
  let cls = "panel";
  if (!closepanel) {
   cls += " show";
  } else {
   cls = "panel";
  }
  return (
   <div classname={"tab-header"}>
    <div classname={"tab-header-top border-bottom"}>
     {this.rendertabs()}
    </div>
    <div classname={cls} onclick={() => closepanelaction(()=>{})}>
     <div classname={"panel-inner"}>
      {this.rendercontent()}
     </div>
    </div>
   </div>
  );
 }


 componentdidmount() {
  const { areaslist, tabactions: { loadareas } } = this.props;
  if (areaslist && areaslist.length !== 1) {
   return;
  }
  loadareas();
 }
}

const mapstatetoprops = state => {
 return {
  areaslist: getareaslist(state),
  tabs: gettabs(state),
  actionkey: getactionkey(state),
  closepanel: getclosepanel(state)
 };
};

const mapdispatchtoprops = dispatch => {
 return {
  tabactions: bindactioncreators(tabactions, dispatch),
  hospitalactions: bindactioncreators(hospitalactions, dispatch)
 };
};

export default connect(mapstatetoprops, mapdispatchtoprops)(tabs);

以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持。