我有一个我的 expo 应用程序正在查询的节点后端。 node-express-mongo 后端工作得非常完美,我可以使用 Postman 的 GET 请求进行验证,但我的应用程序中出现未处理的 promise 拒绝网络失败错误
完全错误:
[Unhandled promise rejection: TypeError: Network request failed]
- node_modules/whatwg-fetch/dist/fetch.umd.js:473:29 in xhr.onerror
- node_modules/event-target-shim/dist/event-target-shim.js:818:39 in EventTarget.prototype.dispatchEvent
- node_modules/react-native/Libraries/Network/XMLHttpRequest.js:574:29 in setReadyState
- node_modules/react-native/Libraries/Network/XMLHttpRequest.js:388:25 in __didCompleteResponse
- node_modules/react-native/Libraries/vendor/emitter/EventEmitter.js:190:12 in emit
- node_modules/react-native/Libraries/BatchedBridge/MessageQueue.js:436:47 in __callFunction
- node_modules/react-native/Libraries/BatchedBridge/MessageQueue.js:111:26 in __guard$argument_0
- node_modules/react-native/Libraries/BatchedBridge/MessageQueue.js:384:10 in __guard
- node_modules/react-native/Libraries/BatchedBridge/MessageQueue.js:110:17 in __guard$argument_0
* [native code]:null in callFunctionReturnFlushedQueue
这是我的代码:
api.js
export const fetchMeetups = () =>
fetch('http://localhost:3000/api/meetups')
.then(res => res.json());
应用.js
import * as React from 'react';
import { Platform, StyleSheet, Text, View, ActivityIndicator } from 'react-native';
import { fetchMeetups } from './constants/api';
const instructions = Platform.select({
ios: `Press Cmd+R to reload,\nCmd+D or shake for dev menu`,
android: `Double tap R on your keyboard to reload,\nShake or press menu button for dev menu`,
});
class App extends React.Component{
static defaultProps = {
fetchMeetups
}
state = {
loading: false,
meetups: []
}
async componentDidMount(){
this.setState({loading: true});
const data = await this.props.fetchMeetups();
setTimeout(() => this.setState({loading: false, meetups: data.meetups}),2000)
}
render(){
if(this.state.loading){
return(
<ActivityIndicator size="large"/>
)
}
return (
<View style={styles.container}>
<Text>MeetupME</Text>
</View>
);
}
}
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,
},
});
index.js
import { registerRootComponent } from 'expo';
import App from './App';
// registerRootComponent calls AppRegistry.registerComponent('main', () => App);
// It also ensures that whether you load the app in the Expo client or in a native build,
// the environment is set up appropriately
registerRootComponent(App);
- - - - - - - 更新 - - - - - - - - -
添加了一个 catch block 来获取并获取这个新错误
Network request failed
- node_modules/whatwg-fetch/dist/fetch.umd.js:473:29 in xhr.onerror
- node_modules/event-target-shim/dist/event-target-shim.js:818:39 in EventTarget.prototype.dispatchEvent
- node_modules/react-native/Libraries/Network/XMLHttpRequest.js:574:29 in setReadyState
- node_modules/react-native/Libraries/Network/XMLHttpRequest.js:388:25 in __didCompleteResponse
- node_modules/react-native/Libraries/vendor/emitter/EventEmitter.js:190:12 in emit
- node_modules/react-native/Libraries/BatchedBridge/MessageQueue.js:436:47 in __callFunction
- node_modules/react-native/Libraries/BatchedBridge/MessageQueue.js:111:26 in __guard$argument_0
- node_modules/react-native/Libraries/BatchedBridge/MessageQueue.js:384:10 in __guard
- node_modules/react-native/Libraries/BatchedBridge/MessageQueue.js:110:17 in __guard$argument_0
* [native code]:null in callFunctionReturnFlushedQueue
最佳答案
React-native Expo 和 Python Django 后端有同样的问题。
问题是关于模拟器本地主机和服务器本地主机之间的冲突。
您的后端服务器可能在 127.0.0.1:8000 上运行,但模拟器无法找到它。
在终端中使用命令“ipconfig”找到您的 IPv4 地址。
例如,它将是 192.138.1.40
在此之后将其放入您的 fetch (
' http://192.138.1.40:8000/ ')。
还有什么也很重要 - 使用相同的主机和端口运行您的后端服务器。
例如在 python Django 上:
py manage.py runserver 192.138.1.40:8000
在 Django 上,您还需要在 settings.py 中添加 ALLOWED_HOSTS = ['192.138.1.40']
关于android - 未处理的 promise 拒绝 : TypeError: Network request failed expo node backend,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/62031415/