1传入一个对象

import React, { Component } from 'react'
export default class App extends Component {
  clickHandle=()=>{
    const {count}=this.state
    this.setState({
      count:count+1
    },()=>{
      //这里可以拿到最新的count值
      console.log(this.state.count)
    })
  }
  state={
    count:0
  }
  render() {
    const {count}=this.state
    return (
      <div>
     <h1>这是一个数据:{count}</h1>
     <button onClick={this.clickHandle}>加一</button>
      </div>
    )
  }
}

2.传入一个函数

import React, { Component } from 'react'
export default class App extends Component {
  clickHandle=()=>{
    this.setState((state,props)=>{
        return{
            count:state.count+1
        }
    },()=>{
      console.log(this.state.count)
    })
  }
  state={
    count:0
  }
  render() {
    const {count}=this.state
    return (
      <div>
     <h1>这是一个数据:{count}</h1>
     <button onClick={this.clickHandle}>加一</button>
      </div>
    )
  }
}