React Native入门基础
2017-08-01 14:11
731 查看
Props(属性)
组件创建的时候会使用很多参数来绘制,这些参数就是props。用法样例一:以Image为例,用prop来指定显示图片的地址,然后传给source用法样例二:自定义的组件使用props
import React, {Component} from 'react'; import {AppRegistry, Image, Text, View} from 'react-native'; class Bananas extends Component { render() { //样例一 let pic = { uri: 'https://upload.wikimedia.org/wikipedia/commons/d/de/Bananavarieties.jpg' }; return ( <View style={{alignItems: 'center'}}> <Image source={pic} style={{width: 193, height: 110}}/> <Greeting name='Rexxar'/> <Greeting name='Jaina'/> <Greeting name='Valeera'/> </View> ); } } //样例二 class Greeting extends Component { render() { return ( <Text>Hello {this.props.name}!</Text> ); } } AppRegistry.registerComponent('reactnativeapp', () => Bananas);运行截图:
State (状态)
props是在父组件中指定,而且一经指定,在被指定的组件的生命周期中则不再改变。 对于需要改变的数据,我们需要使用
state,一般state在构造用法样例:制作一段不停闪烁的文字
import React, { Component } from 'react';import { AppRegistry, Text, View } from 'react-native';class Blink extends Component {constructor(props) {super(props);this.state = { showText: true };// 每1000毫秒对showText状态做一次取反操作setInterval(() => {this.setState(previousState => {return { showText: !previousState.showText };});}, 1000);}render() {// 根据当前showText的值决定是否显示text内容let display = this.state.showText ? this.props.text : ' ';return (<Text>{display}</Text>);}}class BlinkApp extends Component {render() {return (<View><Blink text='I love to blink' /><Blink text='Yes blinking is so great' /><Blink text='Why did they ever take this out of HTML' /><Blink text='Look at me look at me look at me' /></View>);}}AppRegistry.registerComponent('reactnativeapp', () => BlinkApp);
style(样式)
样式名基本上是遵循了web上的CSS的命名,只是按照JS的语法要求使用了驼峰命名法。style属性可以是一个普通的JavaScript对象。还可以传入一个数组——在数组后面的属性会覆盖前面的属性,这样你可以间接实现样式的继承。用法样例:
StyleSheet.create来集中定义组件的样式
import React, {Component} from 'react';import {AppRegistry, StyleSheet, Text, View} from 'react-native';class LotsOfStyles extends Component {render() {return (<View><Text style={styles.red}>just red</Text><Text style={styles.bigblue}>just bigblue</Text><Text style={[styles.bigblue, styles.red]}>bigblue, then red</Text><Text style={[styles.red, styles.bigblue]}>red, then bigblue</Text></View>);}}const styles = StyleSheet.create({bigblue: {color: 'blue',fontWeight: 'bold',fontSize: 30,},red: {color: 'red',},});AppRegistry.registerComponent('reactnativeapp', () => LotsOfStyles);运行截图:
布局
Flex
flex相对于android布局的权重weight,
flex:1代表撑满所有剩余的空间。如果父容器既没有固定的
width和
height,也没有设定
flex,则父容器的尺寸为零。
Flexbox
使用flexbox规则来指定某个组件的子元素的布局flexDirection是指定主轴,子元素是沿着vertical轴(
column)[b],[/b]还是沿着[b]horizontal轴(
row)方向排列。[/b]
justifyContent可以决定其子元素沿着[b]主轴的排列方式。子元素是应该靠近主轴的起始端还是末尾段分布呢?亦或应该均匀分布?对应的这些可选项有:
flex-start、
center、
flex-end、
space-around以及
space-between。[/b]
alignItems可以决定其子元素沿着[b]次轴(与主轴垂直的轴,比如若主轴方向为
row,则次轴方向为
column)的排列方式。子元素是应该靠近次轴的起始端还是末尾段分布呢?亦或应该均匀分布?对应的这些可选项有:
flex-start、
center、
flex-end以及
stretch。[/b]注意:要使
stretch选项生效的话,子元素在次轴方向上不能有固定的尺寸。以下面的代码为例:只有将子元素样式中的
width: 50去掉之后,
alignItems: 'stretch'才能生效。
import React, { Component } from 'react';import { AppRegistry, View } from 'react-native';class FlexDirectionBasics extends Component {render() {return (// 尝试把`flexDirection`改为`row`看看<View style={{flex: 1, flexDirection: 'column', justifyContent: 'center',alignItems: 'center'}}><View style={{width: 50, height: 50, backgroundColor: 'powderblue'}} /><View style={{width: 50, height: 50, backgroundColor: 'skyblue'}} /><View style={{width: 50, height: 50, backgroundColor: 'steelblue'}} /></View>);}};AppRegistry.registerComponent('reactnativeapp', () => FlexDirectionBasics);
布局图解如下:
入门组件使用
TextInput
TextInput是一个允许用户输入文本的基础组件。它有一个名为
onChangeText的属性,此属性接受一个函数,而此函数会在文本变化时被调用。另外还有一个名为
onSubmitEditing的属性,会在文本被提交后(用户按下软键盘上的提交键)调用。用法样例:监听用户输入,如果输入pizza单词就显示delicious,用户按下提交键后显示very delicious
import React, { Component } from 'react';import { AppRegistry, Text, TextInput, View } from 'react-native';class PizzaTranslator extends Component {constructor(props) {super(props);this.state = {text: ''};}render() {let display = this.state.text === 'pizza' ? 'delicious' : this.state.text === 'finish' ? 'very delicious' : ' ';return (<View style={{padding: 10}}><TextInputstyle={{height: 40}}placeholder="Type here to translate!"onChangeText={(text) => this.setState({text})}multiline={false}onSubmitEditing={(event) => this.setState({text:'finish'})}/><Text style={{padding: 10, fontSize: 42}}>{display}</Text></View>);}}AppRegistry.registerComponent('reactnativeapp', () => PizzaTranslator);运行截图:
ScrollV
iew
ScrollView不仅可以垂直滚动,还能水平滚动(通过horizontal属性来设置)。
import React, { Component } from 'react';import{ AppRegistry, ScrollView, Image, Text } from 'react-native'class IScrolledDownAndWhatHappenedNextShockedMe extends Component {render() {return(<ScrollView><Text style={{fontSize:96}}>Scroll me plz</Text><Image source={require('../image/web.png')} /><Image source={require('../image/web.png')} /><Image source={require('../image/web.png')} /><Image source={require('../image/web.png')} /><Image source={require('../image/web.png')} /><Text style={{fontSize:96}}>If you like</Text><Image source={require('../image/web.png')} /><Image source={require('../image/web.png')} /><Image source={require('../image/web.png')} /><Image source={require('../image/web.png')} /><Image source={require('../image/web.png')} /><Text style={{fontSize:96}}>Scrolling down</Text><Image source={require('../image/web.png')} /><Image source={require('../image/web.png')} /><Image source={require('../image/web.png')} /><Image source={require('../image/web.png')} /><Image source={require('../image/web.png')} /><Text style={{fontSize:96}}>What's the best</Text><Image source={require('../image/web.png')} /><Image source={require('../image/web.png')} /><Image source={require('../image/web.png')} /><Image source={require('../image/web.png')} /><Image source={require('../image/web.png')} /><Text style={{fontSize:96}}>Framework around?</Text><Image source={require('../image/web.png')} /><Image source={require('../image/web.png')} /><Image source={require('../image/web.png')} /><Image source={require('../image/web.png')} /><Image source={require('../image/web.png')} /><Text style={{fontSize:80}}>React Native</Text></ScrollView>);}}AppRegistry.registerComponent('reactnativeapp', () => IScrolledDownAndWhatHappenedNextShockedMe);
长列表
RN提供了几个适用于展示长列表数据的组件,一般而言我们会选用FlatList或是SectionList。用法样例一:创建一个FlatList,使用data属性传入预设好的数据,然后通过renderItem渲染包含每一行数据的Text组件。import React, { Component } from 'react';import { AppRegistry, FlatList, StyleSheet, Text, View } from 'react-native';export default class FlatListBasics extends Component {render() {return (<View style={styles.container}><FlatListdata={[{key: 'Devin'},{key: 'Jackson'},{key: 'James'},{key: 'Joel'},{key: 'John'},{key: 'Jillian'},{key: 'Jimmy'},{key: 'Julie'},]}renderItem={({item}) => <Text style={styles.item}>{item.key}</Text>}/></View>);}}const styles = StyleSheet.create({container: {flex: 1,paddingTop: 22},item: {padding: 10,fontSize: 18,height: 44,},})AppRegistry.registerComponent('reactnativeapp', () => FlatListBasics);运行截图:用法样例二:创建一个
SectionList,使用属性sections预设好title和data数据,然后通过renderItem渲染包含每一行
data的Text组件,运行截图:通过renderSectionHeader属性渲染title的Text组件。[code]import React, { Component } from 'react';import { AppRegistry, SectionList, StyleSheet, Text, View } from 'react-native';export default class SectionListBasics extends Component {render() {return (<View style={styles.container}><SectionListsections={[{title: 'D', data: ['Devin']},{title: 'J', data: ['Jackson', 'James', 'Jillian', 'Jimmy', 'Joel', 'John', 'Julie']},]}renderItem={({item}) => <Text style={styles.item}>{item}</Text>}renderSectionHeader={({section}) => <Text style={styles.sectionHeader}>{section.title}</Text>}/></View>);}}const styles = StyleSheet.create({container: {flex: 1,paddingTop: 22},sectionHeader: {paddingTop: 2,paddingLeft: 10,paddingRight: 10,paddingBottom: 2,fontSize: 14,fontWeight: 'bold',backgroundColor: 'rgba(247,247,247,1.0)',},item: {padding: 10,fontSize: 18,height: 44,},})AppRegistry.registerComponent('reactnativeapp', () => SectionListBasics);
网络
使用Fecth
RN提供了web标准一致的Fetch API ,用于满足开发者访问网络的需求。用法样例:通过网络请求腾讯优图身份证识别,获取身份证信息import React, {Component} from 'react';import {AppRegistry,StyleSheet,Text,View,Image,Button} from 'react-native';export default class AndroidIos extends Component {constructor(props) {super(props);this.state = {name: '',id: '',address: '',uri: 'https://opentest.youtu.qq.com/content/img/product/ocr/ocr_id_02.jpg?v=2.0'};}onButtonPress = () => {//将网址作为参数传递给fetchfetch('http://api.youtu.qq.com/youtu/ocrapi/idcardocr', {//你可以指定header参数,或是指定使用POST方法,又或是提交数据等method: 'POST',headers: {'Accept': '*!/!*','Content-Type': 'text/json','user-agent': 'youtu-android-sdk','Authorization': 'Zp0X4NG2VfmukwMYipvy/Ipp0fNhPTEwMDg3NjAyJms' +'9QUtJRDF2ZlJPYndmYU1DdWVGQU90UkNHUGcxS1daUjdLRjFuJmU9MTUwMj' +'k0MDQyNiZ0PTE1MDAzNDg0MjYmcj04MTMwNzQxOTgmdT04Mzk2NDMzOTg=',},body: JSON.stringify({'app_id': '10087602','url': 'http://opentest.youtu.qq.com/content/img/product/ocr/ocr_id_02.jpg?v=2.0','card_type': 0,})//处理服务器的响应数据}).then((response) => response.json()).then((responseJson) => {//var base64Icon = 'data:image/png;base64,' + responseJson.frontimage;this.setState({name: responseJson.name,id: responseJson.id,address: responseJson.address,//uri: base64Icon})}).catch((error) => {console.warn('fetch error')});};render() {return (<View style={styles.container}><Image source={{uri: this.state.uri}}style={styles.image}/><Button title="请求网络" onPress={this.onButtonPress}/><View style={styles.id}><Text>{this.state.name}</Text><Text>{this.state.id}</Text><Text>{this.state.address}</Text></View></View>);}}const styles = StyleSheet.create({container: {flex: 1,justifyContent: 'center',alignItems: 'center',backgroundColor: '#F5FCFF',},id: {flex: 1,flexDirection: 'column',backgroundColor: '#F5FCFF',marginTop: 20},image:{height: 200,width: 300,margin: 10,},});AppRegistry.registerComponent('reactnativeapp', () => AndroidIos);运行截图:最后,我把上面的基础学习的代码放在了github上,地址:https://github.com/Eric0liang/RNProject,apk下载地址:https://github.com/Eric0liang/RNProject/blob/master/app-release.apk?raw=true对于如何生产集成到android studio并生产apk,可以参考另一篇博客 《React Native集成到现有Android Studio项目》
相关文章推荐
- React Native入门基础框架
- React-Native 基础学习入门指南
- React Native基础&入门教程:以一个To Do List小例子,看props和state
- React native最基础的入门知识点
- React Native基础与入门(二)--初识React Native
- React Native基础&入门教程:以一个To Do List小例子,看props和state
- ReactNative开发(二)之基础与入门
- React Native 入门基础学习
- React Native基础&入门教程:调试React Native应用的一小步
- React Native基础入门之调试React Native应用的一小步
- React Native入门基础——Props
- React Native基础&入门教程:调试React Native应用的一小步
- React Native基础入门之初步使用Flexbox布局
- React Native基础与入门(一)--搭建开发环境
- react-native 基础入门
- React Native基础&入门教程:初步使用Flexbox布局
- ReactNative基础(四)了解ListView的使用、实现GridView效果、编写一个真实网络请求案例
- React Native 从入门到原理
- react-native 基础知识的学习
- react-native基础教程(1)