我的博览会应用程序正在查询一个节点后端。 node-express-mongo 后端工作得非常完美,我可以使用来自 Postman 的 GET 请求进行验证,但我在我的应用程序中收到未处理的承诺拒绝 Network Failed 错误
完整错误:
[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());
App.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 块来获取并获取此新错误
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