1 用法
我们一般喜欢把js里面的函数作为参数传递给另外一个函数,然后再调用这个函数,有点像C语言里面的函数指针
2 代码测试
写了一个函数,2个参数分别是函数,然后更具数据决定调用哪个函数
/**
* Sample React Native App
* https://github.com/facebook/react-native
*
* @format
* @flow
*/
import React,{Component} from 'react';
import {Platform,StyleSheet,Text,View,NativeModules} 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',});
export default class App extends Component<Props> {
constructor(props){
super(props);
this.state={
myName:'chenzixuan',}
}
componentDidMount() {
this.load((name) => {console.log(name);},(name) => {console.log(name); console.log(name);});
}
render() {
return (
<View style={styles.container}>
<Text onPress={()=> this._androidShowMsg()} style={styles.welcome}>Welcome to React Native!</Text>
<Text style={styles.instructions}>To get started,edit App.js</Text>
<Text style={styles.instructions}>{instructions}</Text>
<Text style={styles.instructions}>{this.state.myName}</Text>
</View>
);
}
load = (resolve,callback) => {
let name = this.state.myName;
if (name === 'chenzi1xuan') {
resolve(name);
} else {
callback(name);
}
};
}
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,});
3 结果打印如下
很明显,我们会调第二个参数的函数,所以日志会打印两次name,日志如下
ReactNativeJS I Running application "pro_react" with appParams: {"rootTag":1}. __DEV__ === false,development-level warning are OFF,performance optimizations are ON
I chenzixuan
I chenzixuan