3

我有一个返回其他组件的任务组件。但是，当我从 Tasks 组件更改子组件之一的状态时，它不会重新渲染。

我将“newTaskAdded”状态从父级传递给子级作为道具并将其分配给子级状态以重新渲染子组件，但它仍然没有发生。

我的目标是：当用户添加任务时，我希望它立即显示在屏幕上，这意味着用户必须刷新页面才能看到新任务。

任务.jsx：

import React , { Component } from 'react'
import axios from 'axios'
import Name from './Name.jsx'
import ShowTasks from './ShowTasks.jsx'

class Tasks extends Component {
  constructor(props) {
    super(props)
    this.state={
      task: '',
      newTaskAdded:false,
      newTask:[],
    }
    this.handleChange = this.handleChange.bind(this)
    this.addTask = this.addTask.bind(this)
  }
  handleChange(event) {
    this.setState({task: event.target.value})
  }
  addTask() {
    axios.post('/api/addtask',{
      name:this.props.name,
      task:this.state.task
    })
    .then((res) => {
      if(res.status=='200'){
        this.setState ({task:''})
        this.setState ({newTaskAdded:true})
        this.setState ({newTask: res.data.message[res.data.message.length-1] })
      }
    })
    .catch((err) => {
      if(err) throw err
    })
  }

  render() {
    return (
      <div>
        <div>
          <Name name={this.props.name} />
        </div>
        <div>
          <input value={this.state.task} onChange={this.handleChange} type="text" name="task" />
          <button type="button" onClick={this.addTask}>Add Task</button>
        </div>
        <ShowTasks name={this.props.name} updated={this.state.newTaskAdded} />
      </div>
    )
  }
}

export default Tasks

ShowTasks.jsx

import React , { Component } from 'react'
import axios from 'axios'
import Completed from './Completed.jsx'
import NotCompleted from './NotCompleted.jsx'

class ShowTasks extends Component {
  constructor(props) {
    super(props)
    this.state = {
      tasks:[],
      updated:this.props.updated
    }
  }
  componentWillMount(){
    axios.post('/api/loadtasks', {
      name: this.props.name
    })
    .then((res) => {
      console.log('res', res);
      this.setState ({tasks:res.data.tasks})
    })
    .catch((err) => {
      throw err
    })
  }
  render() {
    return (
      <div className='pointer'>
        {this.state.tasks.map((task) => {
          if(task.completed) {
            return <Completed key={task._id} {...task} />
          }
          else {
            return <NotCompleted key={task._id} {...task} />
          }
        })}
      </div>
    )
  }
}

export default ShowTasks
4

2 回答 2

2

所以问题出在你的子函数中，你将道具设置为状态，

您在构造函数中将道具设置为状态，并且不会在每次道具更改时调用构造函数，而只会在组件第一次渲染时调用构造函数，因此不会使用正确的值更新状态。

您应该在 componentWillReceiveProps 函数中设置道具，该函数在父组件的每次渲染时调用

class ShowTasks extends Component {
  constructor(props) {
    super(props)
    this.state = {
      tasks:[],
      updated:this.props.updated
    }
  }
  componentWillReceiveProps(nextProps) {
      this.setState({updated: nextProps.updated});
  }
  componentWillMount(){
    axios.post('/api/loadtasks', {
      name: this.props.name
    })
    .then((res) => {
      console.log('res', res);
      this.setState ({tasks:res.data.tasks})
    })
    .catch((err) => {
      throw err
    })
  }
  render() {
    return (
      <div className='pointer'>
        {this.state.tasks.map((task) => {
          if(task.completed) {
            return <Completed key={task._id} {...task} />
          }
          else {
            return <NotCompleted key={task._id} {...task} />
          }
        })}
      </div>
    )
  }
}

export default ShowTasks

在此处阅读有关生命周期函数以及何时使用它们的更多信息：

于 2017-05-06T13:19:25.540 回答
0

好的！解决了：

任务.jsx：

import React , { Component } from 'react'
import axios from 'axios'
import Name from './Name.jsx'
import ShowTasks from './ShowTasks.jsx'

class Tasks extends Component {
  constructor(props) {
    super(props)
    this.state={
      user:this.props.user,
      task:'',
      newTask:[],
    }
    this.handleChange = this.handleChange.bind(this)
    this.addTask = this.addTask.bind(this)
  }

  handleChange(event) {
    this.setState({task: event.target.value})
  }

  addTask() {
    axios.post('/api/addtask',{
      name:this.state.user.name,
      task:this.state.task
    })
    .then((res) => {
      if(res.status=='200'){
        this.setState ({user:this.state.user})
        this.setState ({newTask: res.data.message[res.data.message.length-1] })
      }
    })
    .catch((err) => {
      if(err) throw err
    })
  }

  render() {
    return (
      <div>
        <div>
          <Name name={this.props.user.name} />
        </div>
        <div>
          <input value={this.state.task} onChange={this.handleChange} type="text" name="task" />
          <button type="button" onClick={this.addTask}>Add Task</button>
        </div>
        <ShowTasks user={this.state.user}/>
      </div>
    )
  }
}

export default Tasks

ShowTasks.jsx：

import React , { Component } from 'react'
import axios from 'axios'
import Completed from './Completed.jsx'
import NotCompleted from './NotCompleted.jsx'

class ShowTasks extends Component {
  constructor(props) {
    super(props)
    this.state = {
      user: this.props.user,
      tasks:[],
    }
    this.loadTasks=this.loadTasks.bind(this)
  }

  loadTasks() {
    axios.post('/api/loadtasks', {
      name: this.state.user.name
    })
    .then((res) => {
      this.setState ({tasks:res.data.tasks})
    })
    .catch((err) => {
      throw err
    })
  }

  componentWillReceiveProps(nextProps) {
    this.loadTasks()
  }

  render() {
    return (
      <div className='pointer'>
        {this.state.tasks.map((task) => {
          if(task.completed) {
            return <Completed key={task._id} {...task} />
          }
          else {
            return <NotCompleted key={task._id} {...task} />
          }
        })}
      </div>
    )
  }
}

export default ShowTasks
于 2017-05-06T16:37:17.670 回答