React Native Flux框架的使用

React Native Flux框架的使用

Flux是RN比较常用的框架，用起来相对比较简单和方便。Flux实现的原理不再说明。这里只做Flux在项目中的具体使用。

使用Flux首先需要安装Flux包

npm install flux

创建flux文件

• 创建dispatcher.js -> dispatcher

var Dispatcher = require('flux').Dispatcher;
module.exports = new Dispatcher();

• 声明type常量 AppConstants.js

npm install keymirror

keymirror: 在 Closure Compiler 的高级模式下，Object 的 key 会被压缩替换成更短的字符，这样就不能创建一个 key 跟 value 相等的 Object 了。keyMirror 就是解决这个问题的。

import keyMirror from 'keymirror';  [^keymirror]
let AppConstants = keyMirror({
    ADD_NUMBER: null,
    GET_NUMBER: null,
});
    
export default AppConstants;

• 创建AppActions.js -> action

import AppDispatcher from '../dispatcher/AppDispatcher';
import AppConstants from '../constants/AppConstants';

let AppActions = {

    addNumberAction(num) {
        // 加上num 
        AppDispatcher.dispatch({
            actionType: AppConstants.ADD_NUMBER,
            num: num
        });
    },
    getNumberAction(){
        //获取最新的数组
        AppDispatcher.dispatch({
            actionType:AppConstants.GET_NUMBER,
        })
    }
};

export default AppActions;

• 创建AppStore -> store

import {EventEmitter} from 'events';
import assign from 'object-assign';
import AppDispatcher from '../dispatcher/AppDispatcher';
import AppConstants  from '../constants/AppConstants';
let CHANGE_EVENT = 'change';

const AppStore = assign({}, EventEmitter.prototype, {

    num: 100, //初始化

    addNumber: function(number) {
        this.num += number;
        // alert(this.num);

        return this.num;
    },
    getNumber: function() {

        return this.num;

    },
    emitChange: function() {

        this.emit(CHANGE_EVENT);
    },

    addChangeListener: function(callback) {
        this.on(CHANGE_EVENT, callback);
    },

    removeChangeListener: function(callback) {
        this.removeListener(CHANGE_EVENT, callback);
    }

})

// Register callback to handle all updates
AppDispatcher.register((action) =>{

    switch(action.actionType) {

        case AppConstants.ADD_NUMBER:
            // _getStateMessage(action.num);
            AppStore.addNumber(action.num);
            AppStore.emitChange()

            //alert(action.num);
            break;
        case AppConstants.GET_NUMBER:
            AppStore.getNumber();
            AppStore.emitChange()
            break;

        case AppConstants.SET_MESSAGE:
            AppStore.emitChange();
            break;

        default:
    }

});
export default AppStore;

在项目中使用

此项目实现效果为A页面数字 Push到 B 页面 B页面对数字进行添加 pop回A页面 A页面数字改变

A.js

import React, { Component } from 'react'
import {
    Navigator,
    Text,
    View,
    AsyncStorage,
    TouchableHighlight
} from 'react-native'
import SecondPage from './SecondPage'
import AppStore from './stores/AppStore'
// import AppActions from './actions/AppActions'
export default class HomePage extends Component
{
    constructor(props) {
        super(props);
        this.state = {
            number:100
        }
    }
    componentDidMount() {
        AppStore.addChangeListener(this._onChange.bind(this));
    }

    componentWillUnmount() {
        AppStore.removeChangeListener(this._onChange.bind(this));
    }
    _onChange() {
        this.setState({
            number: AppStore.getNumber()
        });
    }
    render(){
        return (
            <View style={{flex:1,justifyContent:'center',alignItems: 'center'}}>
                <Text style={{padding:50}}>{this.state.number}</Text>
                <TouchableHighlight onPress={()=>{
                    const navigator = this.props.navigator
                    if (navigator) {
                        navigator.push(
                            {
                                name:'SecondPage',
                                component:SecondPage,
                                params:{
                                    getRegionSelectText:(text)=>{
                                        this.setState({regionSelect:text})
                                    }
                                }
                            }
                        )
                    }

                }}>
                    <Text>下一个页面</Text>
                </TouchableHighlight>

            </View>
        )
    }
}

B.js

import React, { Component } from 'react'
import {
    Navigator,
    Text,
    View,
    AsyncStorage,
    TouchableHighlight
} from 'react-native'
import AppStore from './stores/AppStore'
import AppActions from './actions/AppActions'
export default class SecondPage extends Component
{
    constructor(props) {
        super(props);
        this.state = {
            number:AppActions.getNumberAction()

        }
    }
    componentDidMount() {
        AppStore.addChangeListener(this._onChange.bind(this));
    }
    componentWillUnmount() {
        AppStore.removeChangeListener(this._onChange.bind(this));
    }
    _onChange() {
        this.setState({
            number: AppStore.getNumber()
        });
    }
    render(){
        return (
            <View style={{flex:1,justifyContent:'space-around',alignItems: 'center',backgroundColor:'#eee'}}>
                <Text>{this.state.number}</Text>
                <TouchableHighlight onPress={()=>{
                    AppActions.addNumberAction(10);
                }}>
                    <Text>增加</Text>
                </TouchableHighlight>
                <TouchableHighlight onPress={()=>{
                    const navigator = this.props.navigator
                    if (navigator) {
                        navigator.pop()
                    }
                }}>
                    <Text>返回页面</Text>
                </TouchableHighlight>
            </View>
        )
    }
}

个人理解，不一定正确

Flux 实现state的变化主要是根据EventEmitter进行通知改变。所以使用的页面都有

componentDidMount() {
AppStore.addChangeListener(this._onChange.bind(this));
}

componentWillUnmount() {
AppStore.removeChangeListener(this._onChange.bind(this));
}
_onChange() {
this.setState({
number: AppStore.getNumber()
});
}

三个方法。这三个方法实现并监听了number的变化，并改变state，进行页面的刷新。

初步理解