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

/**
 * 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' 
  },
});