import React, { Component } from 'react';
import {
  AppRegistry,
  StyleSheet,
  Platform,
} from 'react-native';

class App extends Component {
   //构造函数
   constructor(props) {
    super(props);

    if(Platform.OS === "android") {
      //Android平台需要运行的代码
      alert("当前是Android系统。");
    }else{
      //iOS平台需要运行的代码
      alert("当前是iOS系统。");
    }

   }

   render() {
   }
 }

AppRegistry.registerComponent('HelloWorld', () => App);