React主要有如下3个特点：
- 作为UI（Just the UI）
- 虚拟DOM（Virtual DOM）:这是亮点 是React最重要的一个特性 放进内存 最小更新的视图,差异部分更新 diff算法
- 数据流（Date Flow）单向数据流
学习React需要掌握哪些知识？
- JSX语法 类似XML
- ES6相关知识
- 前端基础 CSS+DIV JS
例子一
（简单组件和数据传递） 使用this.props 指向自己的属性
<!DOCTYPE html> <html> <head lang="en"> <Meta charset="UTF-8"> <title>React第一个例子</title> <script type="text/javascript" src="react.js"></script> <script type="text/javascript" src="react-dom.js"></script> <script type="text/javascript" src="browser.min.js"></script> </head> <body> <div id="example"></div> <script type="text/babel"> var HelloMessage=React.createClass( { render:function(){ return <h1 style={{color:'#ff0000',fontSize:'24px'}} >Hello {this.props.name}!我是东方耀</h1>; //这是注释 React.createElement } } ); ReactDOM.render(<HelloMessage name="React 语法基础8" />,document.getElementById('example')); </script> </body> </html>
例子二（通过this.state更新视图）
<!DOCTYPE html>
<html>
<head lang="en">
<Meta charset="UTF-8">
<title>React第二个例子</title>
<script type="text/javascript" src="react.js"></script>
<script type="text/javascript" src="react-dom.js"></script>
<script type="text/javascript" src="browser.min.js"></script>
</head>
<body>
<div id="example"></div>
<script type="text/babel"> var Timer=React.createClass( { /*初始状态*/ getInitialState:function(){ return {secondsElapsed:0}; },tick:function(){ this.setState({secondsElapsed:this.state.secondsElapsed+1}); },/*组件完成装载*/ componentDidMount:function(){ this.interval=setInterval(this.tick,1000); },/*组件将被卸载 清除定时器*/ componentWillUnmount:function(){ clearInterval(this.interval); },/*渲染视图*/ render:function(){ return( <div> Seconds Elapsed:{this.state.secondsElapsed} </div> ); } } ); React.render( <Timer />,document.getElementById('example')); </script>
</body>
</html>
例子三（简单应用）
<!DOCTYPE html> <html> <head lang="en"> <Meta charset="UTF-8"> <title>React第三个例子</title> <script type="text/javascript" src="react.js"></script> <script type="text/javascript" src="react-dom.js"></script> <script type="text/javascript" src="browser.min.js"></script> </head> <body> <div id="example"></div> <script type="text/babel"> var ShowEditor=React.createClass( { getInitialState:function(){ return {value:'你可以在这里输入文字'}; },handleChange:function(){ this.setState({value:React.findDOMNode(this.refs.textarea).value}); },render:function(){ return ( <div> <h3>输入</h3> <textarea style={{width:300,height:150,outline:'none'}} onChange={this.handleChange} ref="textarea" defaultValue={this.state.value} /> <h3>输出</h3> <div> {this.state.value} </div> </div> ); } } ); React.render(<ShowEditor />,document.getElementById('example')); </script> </body> </html>
flexBox布局
伸缩项目的属性
1.order
定义项目的排列顺序，数值越小，排列越靠前，默认值为0，语法为：order：整数值
2.flex-grow
定义伸缩项目的放大比例，默认值为0，即表示如果存在剩余空间，也不放大，语法为：flex-grow：整
数值
3.flex-shrink
定义伸缩项目的收缩能力，默认值为1 ，其语法为：flex-shrink:整数值
4.flex-basis
用来设置伸缩项目的基准值，剩余的空间按比率进行伸缩，其语法为：flex-basis:length | auto，默认
值为auto
5.flex
是flex-grow flex-shrink flex-basis这三个属性的缩写，其语法为：flex:none | flex-grow flex-shrink flexbasis，
其中第二个和第三个参数为可选参数，默认值为：0 1 auto
6.align-self
用来设置单独的伸缩项目在交叉轴上的对齐方式，会覆盖默认的对齐方式，其语法为：align-self:auto
| flex-start | flex-end | center | baseline | stretch(伸缩项目在交叉轴方向占满伸缩容器，如果交叉轴为
垂直方向的话，只有在不设置高度的情况下才能看到效果)
在React Native中使用flexBox
RN目前主要支持flexBox的如下6个属性：
1.alignItems
用来定义伸缩项目在交叉轴上的对齐方式，语法为： alignItems:flex-start（默认值） | flex-end |
center | stretch
2.alignSelf
用来设置单独的伸缩项目在交叉轴上的对齐方式，会覆盖默认的对齐方式，其语法为：alignSelf:auto |
flex-start | flex-end | center | stretch(伸缩项目在交叉轴方向占满伸缩容器，如果交叉轴为垂直方向的
话，只有在不设置高度的情况下才能看到效果)
3.flex
是flex-grow flex-shrink flex-basis这三个属性的缩写，其语法为：flex:none | flex-grow flex-shrink flexbasis，
其中第二个和第三个参数为可选参数，默认值为：0 1 auto
4.flexDirection
指定主轴的方向 flex-direction:row| row-reverse | column（默认值） | column-reverse
5.flexWrap
6.justifyContent
Box实现
<!DOCTYPE html>
<html>
<head>
<Meta charset="utf-8">
<title></title>
<style> .height50 { height: 50px; } .height400 { height: 400px; } .height300 { height: 300px; } .height200 { height: 200px; } .height100 { height: 100px; } .width400 { width: 400px; } .bgred { background-color: #6AC5AC; } .bggreen { background-color: #414142; } .bgyellow { background-color: #D64078; } .Box { display: flex; flex-direction: column; flex: 1; position: relative; color: #FDC72F; line-height: 1em; } .label { top: 0; left: 0; padding: 0 3px 3px 0; position: absolute; background-color: #FDC72F; color: white; line-height: 1em; } .top { width: 100%; justify-content: center; display: flex; align-items: center; } .bottom { width: 100%; display: flex; justify-content: center; align-items: center; } .right { width: 50px; display: flex; justify-content: space-around; align-items: center; } .left { width: 50px; display: flex; justify-content: space-around; align-items: center; } .heightdashed { position: absolute; right: 20px; height: 100%; border-left: 1px solid #FDC72F; } .widthdashed { position: absolute; left: 0px; width: 100%; bottom: 24px; border-top: 1px solid #FDC72F; } .margginBox { position:absolute; top: 100px; padding-left:7px; padding-right:7px; } .borderBox { flex: 1; display: flex; justify-content: space-between; } .paddingBox { flex: 1; display: flex; justify-content: space-between; } .elementBox{ flex: 1; display: flex; justify-content: space-between; } .measureBox { flex: 1; display: flex; justify-content: flex-end; align-items: flex-end; } </style>
</head>
<body>
<span class="margginBox">
<span class="Box height400 width400">
<span class="label">
margin
</span>
<span class="top height50 bgred">
top
</span>
<span class="borderBox">
<span class="left bgred">
left
</span>
<span class="Box height300 ">
<span class="label">
border
</span>
<span class="top height50 bggreen">
top
</span>
<span class="paddingBox">
<span class="left bggreen">
left
</span>
<span class="Box height200 ">
<span class="label">
padding
</span>
<span class="top height50 bgyellow">
top
</span>
<span class="elementBox">
<span class="left bgyellow">
left
</span>
<span class="Box height100 ">
<span class="label">
element
</span>
<span class="widthdashed">
</span>
<span class="heightdashed">
</span>
<span class="measureBox">
<span class="right">
height
</span>
</span>
<span class="bottom height50">
width
</span>
</span>
<span class="right bgyellow">
right
</span>
</span>
<span class="bottom height50 bgyellow">
bottom
</span>
</span>
<span class="right bggreen">
right
</span>
</span>
<span class="bottom height50 bggreen">
bottom
</span>
</span>
<span class="right bgred">
right
</span>
</span>
<span class="bottom height50 bgred">
bottom
</span>
</span>
</span>
</body>
</html>
效果如下
ReactNative版实现
/**
* Sample React Native App
* https://github.com/facebook/react-native
*/
'use strict';
import React,{
AppRegistry,Component,StyleSheet,Text,View
} from 'react-native';
class DongFang extends Component {
render() {
return (
<View style={[BoxStyles.margginBox]} ref="lab1">
<View style={[BoxStyles.Box,BoxStyles.height400,BoxStyles.width400]}>
<View style={[BoxStyles.top,BoxStyles.height50,BoxStyles.bgred]}>
<Text style={BoxStyles.yellow}>top</Text></View>
<View style={[BoxStyles.borderBox]}>
<View style={[BoxStyles.left,BoxStyles.bgred]} >
<Text style={BoxStyles.yellow}>left</Text></View>
<View style={[BoxStyles.Box,BoxStyles.height300]}>
<View style={[BoxStyles.top,BoxStyles.bggreen]}>
<Text style={BoxStyles.yellow}>top</Text></View>
<View style={[BoxStyles.paddingBox]}>
<View style={[BoxStyles.left,BoxStyles.bggreen]} >
<Text style={BoxStyles.yellow}>left</Text></View>
<View style={[BoxStyles.Box,BoxStyles.height200]}>
<View style={[BoxStyles.top,BoxStyles.bgyellow]}>
<Text style={BoxStyles.yellow}>top</Text></View>
<View style={[BoxStyles.elementBox]}>
<View style={[BoxStyles.left,BoxStyles.bgyellow]} >
<Text style={BoxStyles.yellow}>left</Text></View>
<View style={[BoxStyles.Box,BoxStyles.height100]}>
<View style={[BoxStyles.label]}>
<Text style={BoxStyles.white}>element</Text></View>
<View style={[BoxStyles.widthdashed]} ></View>
<View style={[BoxStyles.heightdashed]} ></View>
<View style={[BoxStyles.measureBox]} >
<View style={[BoxStyles.right]}>
<Text style={[BoxStyles.yellow]}>height</Text></View>
</View>
<View style={[BoxStyles.bottom,BoxStyles.height50]}>
<Text style={BoxStyles.yellow}>width</Text></View>
</View>
<View style={[BoxStyles.right,BoxStyles.bgyellow]}><Text style={BoxStyles.yellow}>right</Text></View>
</View>
<View style={[BoxStyles.bottom,BoxStyles.bgyellow]}>
<Text style={BoxStyles.yellow}>bottom</Text></View>
<View style={[BoxStyles.label]}>
<Text style={BoxStyles.white}>padding</Text></View>
</View>
<View style={[BoxStyles.right,BoxStyles.bggreen]}><Text style={BoxStyles.yellow}>right</Text></View>
</View>
<View style={[BoxStyles.bottom,BoxStyles.bggreen]}>
<Text style={BoxStyles.yellow}>bottom</Text></View>
<View style={[BoxStyles.label]}><Text style={BoxStyles.white}>border</Text></View>
</View>
<View style={[BoxStyles.right,BoxStyles.bgred]}>
<Text style={BoxStyles.yellow}>right</Text></View>
</View>
<View style={[BoxStyles.bottom,BoxStyles.bgred]}>
<Text style={BoxStyles.yellow}>bottom</Text></View>
<View style={[BoxStyles.label]} ><Text style={BoxStyles.white}>margin</Text></View>
</View>
</View>
);
}
}
const BoxStyles = StyleSheet.create({
height50:{
height: 50,},height400:{
height: 400,height300:{
height: 300,height200:{
height: 200,height100:{
height: 100,width400:{
width: 400,width300:{
width: 300,width200:{
width: 200,width100:{
width: 100,bgred: {
backgroundColor:'#6AC5AC',bggreen: {
backgroundColor: '#414142',bgyellow: {
backgroundColor: '#D64078',Box: {
flexDirection: 'column',flex: 1,position: 'relative',label: {
top: 0,left: 0,paddingTop: 0,paddingRight: 3,paddingBottom: 3,paddingLeft: 0,position: 'absolute',backgroundColor: '#FDC72F',top: {
justifyContent: 'center',alignItems: 'center',bottom: {
justifyContent: 'center',right: {
width: 50,justifyContent: 'space-around',left: {
width: 50,heightdashed: {
bottom: 0,top: 0,right: 20,borderLeftWidth: 1,borderLeftColor: '#FDC72F',widthdashed: {
bottom: 25,right: 0,borderTopWidth: 1,borderTopColor: '#FDC72F',yellow: {
color: '#FDC72F',fontWeight:'900',white: {
color: 'white',margginBox:{
position: 'absolute',top: 100,paddingLeft:7,paddingRight:7,borderBox:{
flex: 1,justifyContent: 'space-between',flexDirection: 'row',paddingBox:{
flex: 1,elementBox:{
flex: 1,measureBox:{
flex: 1,justifyContent: 'flex-end',alignItems:'flex-end',container: {
flex: 1,justifyContent: 'center',backgroundColor: '#F5FCFF',welcome: {
fontSize: 20,textAlign: 'center',margin: 10,instructions: {
textAlign: 'center',color: '#333333',marginBottom: 5,});
AppRegistry.registerComponent('DongFang',() => DongFang);
