React Native之js同步调用安卓原生方法@ReactMethod(isBlockingSynchronousMethod = true)

1 问题

之前的代码js调用安卓原生都是用的异步方法,比如callback, promiss,异步的话,我们一般是在安卓原生有耗时操作,才用异步,如果我要离开返回,就需要js调用安卓同步方法

利用callback实现js调用原生可以参考我的这篇博客

React Native实现js调用安卓原生代码

React Native之js调用Android原生使用Callback传递结果给js

 

2  代码实现

依然在MyToastModule.java文件下面增加下面的同步函数

    @ReactMethod(isBlockingSynchronousMethod = true)
    public String showMyName() {
        return "chenyu1";
    }

这里用了注解,请注意,也就是说意味着这个方法是同步方法

然后App.js的部分实现如下

/**
 * 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',
});
var myAndroidToast = NativeModules.MyToast;
type Props = {};
export default class App extends Component<Props> {
   
    constructor(props){
        super(props);
        this.state={
            myName:'chenzixuan',
        }
    }
  
  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>
    );
  }

    _androidShowMsg = () => {
       var value = myAndroidToast.showMyName();
       this.setState({myName:value});
        
    };
}

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 运行结果

点击Welcome to React Native 效果如下