React(5)-编程知识

1.受控组件案例

1.1之前的影院案例改写

import React, { Component } from 'react'
import axios from 'axios'
import BetterScroll from 'better-scroll'
import './css/02_tab.css'export default class Cinema extends Component {constructor() {super();this.state = {cinemaList: [],mytext:''// backcinemaList: []}//react中使用axios第三方的库  专门用来请求数据// axios.get("请求地址").then(res=>{}).catch(err=>{console.log(err);})axios({url: "https://m.maizuo.com/gateway?cityId=110100&ticketFlag=1&k=7406159",method: 'get',headers: {'X-Client-Info': '{"a":"3000","ch":"1002","v":"5.0.4","e":"16395416565231270166529","bc":"110100"}','X-Host': 'mall.film-ticket.cinema.list'}}).then(res => {console.log(res.data)this.setState({cinemaList: res.data.data.cinemas,// backcinemaList: res.data.data.cinemas})new BetterScroll(".wrapper")}).catch(err => console.log(err))}render() {return (<div><div>{/* <input onInput={this.handleInput}></input>实时搜索 */}<input value={this.state.mytext} onChange={(evt)=>{this.setState({mytext:evt.target.value},()=>{console.log(this.state.mytext);})}}></input>实时搜索</div><div className='wrapper' style={{height:'800px',overflow:'hidden'}}><div className='content'>{this.getCinemaList().map((item) =><dl key={item.cinemaId}><dt>{item.name}</dt><dd>{item.address}</dd></dl>)}</div></div></div>)}getCinemaList=()=>{//return this.state.cinemaListreturn this.state.cinemaList.filter(item => item.name.toUpperCase().includes(this.state.mytext.toUpperCase()) ||item.address.toUpperCase().includes(this.state.mytext.toUpperCase()))}// handleInput = (event) => {//     console.log("input", event.target.value);//     // 数组的filter方法不会影响原数组//     var newList = this.state.backcinemaList.filter(item => item.name.toUpperCase().includes(event.target.value.toUpperCase()) ||//         item.address.toUpperCase().includes(event.target.value.toUpperCase()))//     this.setState({//         cinemaList: newList//     })// }
}

1.2 todolist改写


import React, { Component } from 'react'export default class App extends Component {constructor() {super();this.state = {addList: [{id: Math.random()*10000, title: "张三"}],mytext:''}}//myref = React.createRef();render() {return (<div><input value={this.state.mytext} onChange={(evt)=>{this.setState({mytext:evt.target.value})}}></input><button onClick={() => {this.handler()}}>增加</button><ul>{this.state.addList.map((item,index) =><li key={item.id}>{/* {item.id}----{item.title} */}<span dangerouslySetInnerHTML={{__html:item.id+"------"+item.title}}></span><button onClick={()=>{this.deleteList(index)}}>删除</button></li>)}</ul>{/* {this.state.addList.length===0 ?<div>暂无待办事项</div>:null} */}{this.state.addList.length===0 && <div>暂无待办事项</div>}</div>)}handler = () => {let newList = [...this.state.addList]newList.push({id: Math.random()*10000,title: this.state.mytext})this.setState({addList: newList,mytext:''}) }deleteList=(index)=>{console.log(index);let newList = [...this.state.addList];newList.splice(index,1);//从该下标开始删除  删除一个this.setState({addList: newList})}
}

2.父子通信

场景：比如我有一个父组件父组件内部有1个导航组件一个侧边栏组件在导航栏组件中，我做了一个操作后，想让侧边栏组件隐藏与显示

这就需要子传父了导航栏组件传递信号给父组件父组件再去控制侧边栏组件

例如：

父组件：

通过state中的isShow来控制侧边栏组件的显示

import React, { Component } from 'react'
import Navbar from './compoent/Navbar'
import SideBar from './compoent/SideBar'export default class App extends Component {state={isShow:true,}render() {return (<div>           <Navbar/>{this.state.isShow && <SideBar/>}</div>)}
}

侧边栏组件

import React, { Component } from 'react'export default class SideBar extends Component {render() {return (<div style={{background:"green",width:"300px"}}><ul><li>11111</li><li>11111</li><li>11111</li><li>11111</li><li>11111</li><li>11111</li><li>11111</li></ul></div>)}
}

导航栏组件

import React, { Component } from 'react'export default class Navbar extends Component {render() {return (<div style={{background:"yellow",width:"400px"}}><button>控制侧边栏</button></div>)}
}

现在需要去做修改，使用event属性传一个回调函数，然后子组件中调用此函数

可以发现子组件中点击按钮后，已经可以控制父组件中打印了。因此咱后面可以在父组件中修改state中的值了

export default class App extends Component {state={isShow:true,}render() {return (<div>           <Navbar event={()=>{console.log("父组件中可以修改state了");this.setState({isShow:!this.state.isShow})}}/>{this.state.isShow && <SideBar/>}</div>)}
}

总结：

父传子：传属性

子传父：父给子一个函数，子执行此函数当成回调函数

3.父子通信版：表单域组件


import React, { Component } from 'react'
import Field from './compoent/Field'export default class App extends Component {state={username:"",password:""}render() {return (<div><Field label="用户名" type="text" value={this.state.username} onChangeEvent={(value)=>{// console.log("value==="+value);this.setState({username:value})}}></Field><Field label="密码" type="password" value={this.state.password} onChangeEvent={(value)=>{// console.log("value==="+value);this.setState({password:value})}}></Field><button onClick={()=>{console.log(this.state.username+"\t"+this.state.password+"发送给后端校验");}}>登录</button><button onClick={()=>{this.setState({username:"",password:""})}}>重置</button></div>)}
}


import React, { Component } from 'react'export default class Field extends Component {render() {return (<div><label>{this.props.label}</label><input type={this.props.type} value={this.props.value} onChange={(evt)=>{// console.log(evt.target.value);this.props.onChangeEvent(evt.target.value);}}></input></div>)}
}

4.ref版：表单域组件


import React, { Component } from 'react'
import Field2 from './compoent/Field2'export default class App extends Component {username=React.createRef();password=React.createRef();render() {return (<div><Field2 label="用户名" type="text" ref={this.username}></Field2><Field2 label="密码" type="password" ref={this.password}></Field2><button onClick={()=>{console.log(this.username);  //可以发现这里拿到的是Field2这个组件console.log(this.username.current.state.value+"\t"+this.password.current.state.value+"发送给后端校验");}}>登录</button><button onClick={()=>{this.username.current.clear();this.password.current.clear();}}>重置</button></div>)}
}


import React, { Component } from 'react'export default class Field2 extends Component {state={value:""}clear(){this.setState({value:""})}render() {return (<div><label>{this.props.label}</label><input type={this.props.type}  value={this.state.value} onChange={(evt)=>{this.setState({value:evt.target.value})}}></input></div>)}
}

console.log(this.username); //可以发现这里拿到的是Field2这个组件