参考文档：
http://reactnative.cn/docs/next/state.html#content
http://reactnative.cn/docs/next/state.html#content

我们使用两种数据来控制一个组件：props和state.
props定制的内容，一经组件创建，内容不再改变。
需要改变的数据使用state.
使用state
1. 在constructor中初始化state
2. 使用setState修改状态

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

class Blink extends Component {
  constructor(props) {
    super(props);
    this.state = { showText: true };

    // 每秒做一次状态切换
    setInterval(() => {
      this.setState({ showText: !this.state.showText });
    },1000);
  }

  render() {
    let display = this.state.showText ? this.props.text : ' ';
    return (
      <Text>{display}</Text>
    );
  }
}

class BlinkApp extends Component {
  render() {
    return (
      <View>
        <Blink text='I love to blink' />
        <Blink text='Yes blinking is so great' />
        <Blink text='Why did they ever take this out of HTML' />
        <Blink text='Look at me look at me look at me' />
      </View>
    );
  }
}
AppRegistry.registerComponent('BlinkApp',() => BlinkApp);