react 怎么实现淡入淡出

首先要下载一个库，即npm i react-addons-css-transition-group,接下来看代码

//Pic.js

import React,{Component} from 'react'
import Img1 from '../../image/1.jpg'
import Img2 from '../../image/2.jpg'
import Img3 from '../../image/3.jpg'
import Image from './Image'
import Dot from './Dot'
import './pic.css'
class Pic extends Component{
    constructor(props){
        super(props)
        this.state={current:0,
            src:[Img1,Img2,Img3]
        }
        this.timer=null;
    }
    componentDidMount(){
        this.timer=setInterval(()=>{
            this.setState((prev)=>{return{current:(prev.current+1)%3}})
        },3000)
    }
    clear(){
        clearInterval(this.timer);
    }//鼠标移入结束动画
    start(){
        this.timer=setInterval(()=>{
            this.setState((prev)=>{return{current:(prev.current+1)%3}})
        },3000)
    }//鼠标移出开始动画
    change=(i)=>{
        console.log(i)
        this.setState({current:i})
    }//鼠标点击原点切换图片

    render(){
        return(<div className="list" 
        onMouseLeave={this.start.bind(this)}
        onMouseEnter={this.clear.bind(this)}>
            <Image src={this.state.src[this.state.current]} 
            current={this.state.current}
            name="item"
            component={'li'}
            enterDelay={1500}//动画开始所用时间
            leaveDelay={1500}//动画结束所用时间
            ></Image>
            <Dot current={this.state.current} change={this.change}></Dot>
        </div>)


    }

}
export default Pic

Image.js

import React,{Component} from 'react'
import CSSTransitionGroup from 'react-addons-css-transition-group';
import './pic.css'

class Image extends Component{

    constructor(props){
        super(props)
    }

    render(){
        return(
        <ul>
        <CSSTransitionGroup
               component={this.props.component}
               transitionName={this.props.name}
               transitionEnterTimeout={this.props.enterDelay}
               transitionLeaveTimeout={this.props.leaveDelay}
               className={this.props.name}
        >
            <img src={this.props.src}
            key={this.props.src}
            ></img>
        </CSSTransitionGroup>
        </ul>
        )
    }

}

export default Image

Dot.js

import React ,{Component} from 'react'

class Dot extends Component{
    constructor(props){
        super(props)
        this.state={arr:[1,2,3]}
    }
    render(){
        return(<div className="dot">
            <ul>
            {this.state.arr.map((item,index)=>{
                return(<li 
                    onClick={this.props.change.bind(this,index)}
                    key={index}
                    className={[index==this.props.current?'current':'']}></li>)
            })}
            </ul>
        </div>)
    }
}

export default Dot

//css样式
*{margin:0;padding:0;}
.list{width:500px;
     height:400px;
     margin:30px auto;
}
ul{position: relative;
   width:500px;
   height:400px;
   overflow: hidden;
}
li{
    position: absolute;
    list-style: none;}
img{width:500px;
    height:400px;
    }
.item-enter{
    position: absolute;
    opacity: 0;

}
.item-enter-active{opacity:1;
    transition: 1.5s opacity ease-in-out;
}
.item-leave{ position: absolute;
    opacity: 1;}
.item-leave-active{
    opacity: 0;
    transition: 1.5s opacity ease-in-out;
}

.dot{
    position: absolute;
    top:380px;
    left:250px;
  
    width:150px;
    height:50px;
}
.dot ul{width:100%;
        height:100%;
}
.dot li{
    position: static;
    float:left;
    margin-left:10px;
    width:25px;
    height:25px;
    border-radius: 50%;
    border:1px solid deeppink;
    transition:3s;
    list-style:none;}

.current{background-color: gold;}

 推荐学习：《react视频教程》