小编mad*_*arg的帖子

编辑:我不想只在单击按钮时调用handleChange.它与handleClick无关.我在@shubhakhatri回答的评论中给出了一个例子.

我想根据状态更改输入值,值正在改变,但它不会触发handleChange()方法.我该如何触发handleChange()方法？

class App extends React.Component {
  constructor(props) {
    super(props)
    this.state = {
    value: 'random text'
    }
  }
  handleChange (e) {
    console.log('handle change called')
  }
  handleClick () {
    this.setState({value: 'another random text'})
  }
  render () {
    return (
      <div>
        <input value={this.state.value} onChange={this.handleChange}/>
        <button onClick={this.handleClick.bind(this)}>Change Input</button>
      </div>
    )
  }
}

ReactDOM.render(<App />,  document.getElementById('app'))

这是codepen链接:http://codepen.io/madhurgarg71/pen/qrbLjp

总体思路是，有人单击按钮，操作从服务器获取数据并发送它。状态正在更新，页面上的内容正在发生变化。该动作看起来完全像这样：

     export function getPosts(page){
     return function(dispatch){
      axios.get(`${ROOT_URL}/home?page=${page}`)
          .then(response => {
            dispatch ({
            type: FETCH_POSTS,
            payload: response.data        
          })
          })
          .catch((error) => {
            console.log(error)
          });
    }
    }

减速器非常简单：

      export default function(state={}, action){
      switch(action.type){
        case FETCH_POSTS:
        return {posts: action.payload, ...state};
      }
      return state;
    }

主页看起来就像这样：

    import React, { Component } from 'react';
    import * as actions from '../actions';
    import RequireAuth from './auth/require_auth';
    import { connect } from 'react-redux';
    import { compose } from 'redux';
    class Home extends Component {

    constructor(props) {
      super(props);
      this.state …

一个简单的hello word程序被编译,但是当我运行它时,我得到以下异常.

Exception in thread "main" java.lang.UnsupportedClassVersionError: a (Unsupported major.minor version 51.0)
    at java.lang.ClassLoader.defineClass0(Native Method)
    at java.lang.ClassLoader.defineClass(Unknown Source)
    at java.security.SecureClassLoader.defineClass(Unknown Source)
    at java.net.URLClassLoader.defineClass(Unknown Source)
    at java.net.URLClassLoader.access$100(Unknown Source)
    at java.net.URLClassLoader$1.run(Unknown Source)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.net.URLClassLoader.findClass(Unknown Source)
    at java.lang.ClassLoader.loadClass(Unknown Source)
    at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
    at java.lang.ClassLoader.loadClass(Unknown Source)
    at java.lang.ClassLoader.loadClassInternal(Unknown Source)
    Could not find the main class:HelloWorldApp.Program will exit.

我有java版本1.6.0_21

我的计划是:

class HelloWorldApp { 
   public static void main(String[] args) { 
   System.out.println("Hello World!"); // Display the string. 
   }
}

我想初始化一个2d数组,其所有元素都是0.我试过这个:

scanf("%d",&n);
int arr[n][n]={0};

但我得到了[错误]:"可能无法初始化可变大小的对象"

那么,怎么做呢？