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

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