了解index.ios.js

1、index.ios.js文件

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

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

export default class MNAPP extends Component {
  render() {
    return (
      <View style={styles.container}>
        <Text style={styles.welcome}>
          React-Native 入门学习
        </Text>
        <Text style={styles.instructions}>
          To get started, edit index.ios.js
        </Text>
        <Text style={styles.instructions}>
          Press Cmd+R to reload,{'\n'}
          Cmd+D or shake for dev menu
        </Text>
      </View>
    );
  }
}

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

AppRegistry.registerComponent('MNAPP', () => MNAPP);

（1）引入其他模块

import React, { Component } from 'react';

（2）批量定义组件

import {
  AppRegistry,
  StyleSheet,
  Text,
  View
} from 'react-native';

（3）构建MNAPP入口类：render方法用于渲染视图

// JSX的模板语法
export default class MNAPP extends Component {
  render() {
    return (
      <View style={styles.container}>
        <Text style={styles.welcome}>
          React-Native 入门学习
        </Text>
        <Text style={styles.instructions}>
          To get started, edit index.ios.js
        </Text>
        <Text style={styles.instructions}>
          Press Cmd+R to reload,{'\n'}
          Cmd+D or shake for dev menu
        </Text>
      </View>
    );
  }
}

（4）JS的自面量表达了css样式

const styles = StyleSheet.create({
});

• style是视图的一个属性
• container、welcome、instructions：样式表中的样式

（5）注册应用入口

AppRegistry.registerComponent('MNAPP', () => MNAPP);

2、用Xcode打开AppDelegate.m

(1)标识入口文件

NSURL *jsCodeLocation;
jsCodeLocation = [[RCTBundleURLProvider sharedSettings] jsBundleURLForBundleRoot:@"index.ios" fallbackResource:nil];

(2)接下来尝试修改启动界面：LaunchScreen.xib

（3）添加一张图片

• 导入image

import {
  AppRegistry,
  StyleSheet,
  Text,
  View,
  Image // ①
} from 'react-native';

• 添加样式

export default class MNAPP extends Component {
  render() {
    return (
      <View style={styles.container}>
        <Text style={styles.welcome}>
          React-Native 入门学习
        </Text>
        <Image style={styles.pic} source={{uri: 'https://avatars3.githubusercontent.com/u/6133685?v=3&s=460'}}>
        </Image> // ②
        <Text style={styles.instructions}>
          To get started, edit index.ios.js
        </Text>
        <Text style={styles.instructions}>
          Press Cmd+R to reload,{'\n'}
          Cmd+D or shake for dev menu
        </Text>
      </View>
    );
  }
}

const styles = StyleSheet.create({
  container: {
    flex: 1,
    justifyContent: 'center',
    alignItems: 'center',
    backgroundColor: '#F5FCFF',
  },
  welcome: {
    fontSize: 20,
    textAlign: 'center',
    margin: 10,
    color: 'red',
  },
  instructions: {
    textAlign: 'center',
    color: '#333333',
    marginBottom: 5,
  },
  pic: { // ③
     height: 100,
     width: 100,
  },
});

GitHub：https://github.com/Yangchengfeng/react-native-learning/tree/learnMoreOfIndexIosJS