React Native之Props(属性)和State(状态)和简单样式简单使用

1    Props(属性)和State(状态)和简单样式简单使用App.js代码如下

/**
 * Sample React Native App
 * https://github.com/facebook/react-native
 *
 * @format
 * @flow
 */

import React,{Component} from 'react';
import {Platform,StyleSheet,Text,View,NativeModules,DeviceEventEmitter,Image} from 'react-native';

const instructions = Platform.select({
  ios: 'Press Cmd+R to reload,\n' + 'Cmd+D or shake for dev menu',android:
    'Double tap R on your keyboard to reload,\n' +
    'Shake or press menu button for dev menu',});
var myAndroidToast = NativeModules.MyToast;
type Props = {};

class Greet extends Component {
    render() {
	return (<Text>Hello {this.props.name}</Text>);
    }
}

class Blink extends Component {

    constructor(props){
        super(props);
    	this.state = {isShowing: true};
        setInterval(() => {
            this.setState(previousState => {
            	return {isShowing: !previousState.isShowing};
            });
        },1000);
    }

    render() {
        let display = this.state.isShowing? this.props.text : 'chenyu';
        return(
            <Text>{display}</Text>
        );
    }
}
export default class App extends Component<Props> {
   
   componentWillMount(){  
      //监听事件名为EventName的事件
      DeviceEventEmitter.addListener('EventName',function() {  
          alert("Android send js msg ");  
      });                                
    }
    
    constructor(props){
        super(props);
        this.state={
            myName:'chenzixuan',num:0,isShowingText:true
        }

           // 每1000毫秒对showText状态做一次取反操作
	    setInterval(() => {
	      this.setState(previousState => {
		return {num: ++this.state.num};
	      });
	    },1000);
    }
		
  
  render() {
    let pic = {uri: 'https://upload.wikimedia.org/wikipedia/commons/d/de/Bananavarieties.jpg'};        
    return (
      <View style={styles.container}>
        <Text onPress={()=> this._androidShowMsg()} style={styles.welcome}>Welcome to React Native!</Text>
        <Text style={styles.red}>To get started,edit App.js</Text>
        <Text style={styles.bigblue}>{instructions}</Text>
        <Text style={styles.instructions}>{this.state.myName}</Text>
        <Text style={styles.instructions}>{this.state.num}</Text>
	<Greet name = 'chenyu'></Greet>
        <Blink text = 'chenzixuan'></Blink>
      </View>
    );
  }

    _androidShowMsg = () => {
       var value = myAndroidToast.showMyName();
       this.setState({myName:value});
        
    };
}

const styles = StyleSheet.create({
  container: {
    flex: 1,justifyContent: 'center',alignItems: 'center',backgroundColor: '#F5FCFF',},welcome: {
    fontSize: 20,textAlign: 'center',margin: 10,instructions: {
    textAlign: 'center',color: '#333333',marginBottom: 5,bigblue: {
    color: 'blue',fontWeight: 'bold',fontSize: 39
  },red: {
    color: 'red' 
  },});

 

 

 

 

2   运行结果如下