执行时向我发送以下错误,您知道我做错了什么吗?我使用了发布的代码
不变违规:元素类型无效:预期为字符串(对于内置组件)或类/函数(对于复合组件),但得到:未定义。您可能忘记从定义组件的文件中导出组件,或者您可能混淆了默认导入和命名导入。
检查 FlatListDemo 的渲染方法。
此错误位于:在 FlatListDemo (at withExpoRoot.js:22) in RootErrorBoundary (at withExpoRoot.js:21) in ExpoRootComponent (at renderApplication.js:34) in RCTView (at View.js:44) in RCTView (at View.js:44)在 AppContainer 中(在 renderApplication.js:33)
node_modules\react-native\Libraries\Renderer\oss\ReactNativeRenderer-dev.js:5630:10 在 createFiberFromElement node_modules\react-native\Libraries\Renderer\oss\ReactNativeRenderer-dev.js:9710:8 在 reconcileSingleElement ... 21来自框架内部的更多堆栈帧
import React, { Component } from "react";
import { View, Text, FlatList, ActivityIndicator } from "react-native";
import { List, ListItem, SearchBar } from "react-native-elements";
class FlatListDemo extends Component {
constructor(props) {
super(props);
this.state = {
loading: false,
data: [],
page: 1,
seed: 1,
error: null,
refreshing: false
};
}
componentDidMount() {
this.makeRemoteRequest();
}
makeRemoteRequest = () => {
const { page, seed } = this.state;
const url = `https://randomuser.me/api/?seed=${seed}&page=${page}&results=20`;
this.setState({ loading: true });
fetch(url)
.then(res => res.json())
.then(res => {
this.setState({
data: page === 1 ? res.results : [...this.state.data, ...res.results],
error: res.error || null,
loading: false,
refreshing: false
});
})
.catch(error => {
this.setState({ error, loading: false });
});
};
handleRefresh = () => {
this.setState(
{
page: 1,
seed: this.state.seed + 1,
refreshing: true
},
() => {
this.makeRemoteRequest();
}
);
};
handleLoadMore = () => {
this.setState(
{
page: this.state.page + 1
},
() => {
this.makeRemoteRequest();
}
);
};
renderSeparator = () => {
return (
<View
style={{
height: 1,
width: "86%",
backgroundColor: "#CED0CE",
marginLeft: "14%"
}}
/>
);
};
renderHeader = () => {
return <SearchBar placeholder="Type Here..." lightTheme round />;
};
renderFooter = () => {
if (!this.state.loading) return null;
return (
<View
style={{
paddingVertical: 20,
borderTopWidth: 1,
borderColor: "#CED0CE"
}}
>
<ActivityIndicator animating size="large" />
</View>
);
};
render() {
return (
<List containerStyle={{ borderTopWidth: 0, borderBottomWidth: 0 }}>
<FlatList
data={this.state.data}
renderItem={({ item }) => (
<ListItem
roundAvatar
title={`${item.name.first} ${item.name.last}`}
subtitle={item.email}
avatar={{ uri: item.picture.thumbnail }}
containerStyle={{ borderBottomWidth: 0 }}
/>
)}
keyExtractor={item => item.email}
ItemSeparatorComponent={this.renderSeparator}
ListHeaderComponent={this.renderHeader}
ListFooterComponent={this.renderFooter}
onRefresh={this.handleRefresh}
refreshing={this.state.refreshing}
onEndReached={this.handleLoadMore}
onEndReachedThreshold={50}
/>
</List>
);
}
}
export default FlatListDemo;