React Native Flux框架的使用

Flux是RN比較常用的框架，用起來相對比較簡單和方便侮邀。Flux實現(xiàn)的原理不再說明。這里只做Flux在項目中的具體使用。

使用Flux首先需要安裝Flux包

npm install flux

創(chuàng)建flux文件

• 創(chuàng)建dispatcher.js -> dispatcher

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

• 聲明type常量 AppConstants.js

npm install keymirror

keymirror: 在 Closure Compiler 的高級模式下搀缠，Object 的 key 會被壓縮替換成更短的字符，這樣就不能創(chuàng)建一個 key 跟 value 相等的 Object 了近迁。keyMirror 就是解決這個問題的艺普。

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

• 創(chuàng)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(){
        //獲取最新的數(shù)組
        AppDispatcher.dispatch({
            actionType:AppConstants.GET_NUMBER,
        })
    }
};

export default AppActions;

• 創(chuàng)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;

在項目中使用

此項目實現(xiàn)效果為A頁面數(shù)字 Push到 B 頁面 B頁面對數(shù)字進行添加 pop回A頁面 A頁面數(shù)字改變

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>下一個頁面</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>返回頁面</Text>
                </TouchableHighlight>
            </View>
        )
    }
}

個人理解，不一定正確

Flux 實現(xiàn)state的變化主要是根據(jù)EventEmitter進行通知改變鉴竭。所以使用的頁面都有

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

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

三個方法歧譬。這三個方法實現(xiàn)并監(jiān)聽了number的變化，并改變state搏存，進行頁面的刷新瑰步。

初步理解