React Native的导入导出

1、组件的导入导出方式

问1：如何导出一个组件？

export default class EIComponent extends Component{
  render(){
    return(
      <Text style = {{fontSize:20,backgroundColor:'red'}}>hello.</Text>
    );
  }
}

问2:如何在其他组件中使用导出的组件？

import HelloComponent from './HelloComponent';

2、导出一个或多个变量

问1：如何导出一个或多个变量？

export var name = '小明';
export var age = '22';
// export {name,age};

问2：如何使用导出变量？

import HelloComponent,{name,age} from './HelloComponent';

3、导入导出方法

问1：如何导出方法？

export function sum(a,b){
  return a + b;
}

问2：如何使用导出的方法？

import HelloComponent,{name,age,sum} from './HelloComponent';

实例代码：

　　导出组件、变量、方法

import React, {Component} from 'react';
import {Platform, StyleSheet, Text, View} from 'react-native';
export var name = '小明';
export var age = '22';
// export {name,age};
export default class EIComponent extends Component{
  render(){
    return(
      <Text style = {{fontSize:20,backgroundColor:'red'}}>hello.</Text>
    );
  }
}

export function sum(a,b){
  return a + b;
}

　　使用导出的组件、变量、方法

/**
 * Sample React Native App
 * https://github.com/facebook/react-native
 *
 * @format
 * @flow
 * @lint-ignore-every XPLATJSCOPYRIGHT1
 */

import React, {Component} from 'react';
import {Platform, StyleSheet, Text, View} from 'react-native';
import HelloComponent,{name,age,sum} from './HelloComponent';
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',
});

type Props = {};
export default class App extends Component<Props> {
  constructor(props){
    super(props);
    this.state =({
      result:''
    })
  }
  render() {
    return (
      <View style={styles.container}>
        <Text style ={styles.welcome}>名字:{name}</Text>
        <Text style ={styles.welcome}>年龄:{age}</Text>
        <Text style ={styles.welcome}
              onPress={()=>{
                var result = sum(2,3);
                this.setState({
                    result:result
                })
              }}
        >2+3={this.state.result}</Text>
      </View>

    );
  }
}

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