我在 React Native 中面临有关异步存储的问题
i am facing a problem regarding async storage in react native
我在 React Native 中遇到有关异步存储的问题。
当我在异步存储中设置项目，然后如果有 3 个我添加的任务时检索它，
只检索到其中两个
我会分享前后的照片
this is output before refreshing
this is the output after refreshing the app
这是我的app.js代码
import { StatusBar } from 'expo-status-bar';
import {
StyleSheet,
Text,
View,
KeyboardAvoidingView,
FlatList,
TextInput,
TouchableOpacity,
Keyboard,
} from 'react-native';
import React, { Component } from 'react';
import * as Font from 'expo-font';
import Task from './components/Task';
import AppLoading from 'expo-app-loading';
import AsyncStorage from '@react-native-async-storage/async-storage';
let customFonts = {
Poppins_SemiBold: require('./assets/Poppins-SemiBold.ttf'),
Poppins_Regular: require('./assets/Poppins-Regular.ttf'),
};
export default class App extends Component {
constructor(props) {
super(props);
this.state = {
task: '',
taskItems: [],
fontsLoaded: false,
};
}
async _loadFontsAsync() {
await Font.loadAsync(customFonts);
this.setState({ fontsLoaded: true });
}
componentDidMount() {
this._loadFontsAsync();
this._retrieveData()
}
_retrieveData = async () => {
try {
const value = await AsyncStorage.getItem('data');
if (value.length !== 2) {
// We have data!!
this.setState({taskItems:[...JSON.parse(value)]})
console.log(value);
}
} catch (error) {
// Error retrieving data
console.log(error)
}
};
handleAddTask=()=>{
Keyboard.dismiss()
this.setState({taskItems:[...this.state.taskItems,this.state.task]})
this.setState({task:''})
AsyncStorage.setItem('data',JSON.stringify(this.state.taskItems))
}
deleteItem=(index)=>{
try {
let arr = [...this.state.taskItems];
arr.splice(index, 1);
this.setState({taskItems:arr})
AsyncStorage.setItem('data',JSON.stringify(arr))
} catch (err) {
console.log(err);
}
}
render() {
if (!this.state.fontsLoaded) {
return <AppLoading />;
}
return (
<View style={styles.container}>
{/* Todays Tasks */}
<View style={styles.taskWrapper}>
<Text style={styles.sectionTitle}>Today's Tasks</Text>
<View style={styles.items}>
{/* This is where the tasks will go! */}
<FlatList
data={this.state.taskItems}
keyExtractor={(item) => item}
renderItem={({ item, index }) => (
<Task text={item} handleDelete={() => this.deleteItem(index)} />
)}
/>
</View>
</View>
{/* Write a Task */}
<KeyboardAvoidingView style={styles.writeTaskWrapper}>
<TextInput
style={styles.input}
placeholder={'Write A Task!'}
onChangeText={(text) => {
this.setState({ task: text });
}}
value={this.state.task}
/>
<TouchableOpacity
onPress={() => {
this.handleAddTask();
}}>
<View style={styles.addWrapper}>
<Text style={styles.addText}>+</Text>
</View>
</TouchableOpacity>
</KeyboardAvoidingView>
</View>
);
}
}
const styles = StyleSheet.create({
container: {
flex: 1,
backgroundColor: '#E8EAED',
},
taskWrapper: {
paddingTop: 80,
paddingHorizontal: 20,
},
sectionTitle: {
fontSize: 24,
backgroundColor: '#fff',
fontFamily: 'Poppins_SemiBold',
borderRadius: 10,
margin: 'auto',
width: 250,
height: 60,
textAlign: 'center',
shadowColor: '#000',
shadowOffset: { width: 0, height: 1 },
shadowOpacity: 0.2,
shadowRadius: 2,
elevation: 5,
paddingTop: 10,
},
items: {
marginTop: 30,
},
writeTaskWrapper: {
position: 'absolute',
bottom: 60,
width: '100%',
flexDirection: 'row',
justifyContent: 'space-around',
alignItems: 'center',
},
input: {
paddingVertical: 15,
paddingHorizontal: 15,
backgroundColor: '#fff',
borderRadius: 60,
width: 250,
fontFamily: 'Poppins_Regular',
shadowColor: '#000',
shadowOffset: { width: 0, height: 1 },
shadowOpacity: 0.5,
shadowRadius: 2,
elevation: 3,
},
addWrapper: {
width: 60,
height: 60,
backgroundColor: '#fff',
borderRadius: 60,
justifyContent: 'center',
alignItems: 'center',
shadowColor: '#000',
shadowOffset: { width: 0, height: 1 },
shadowOpacity: 0.5,
shadowRadius: 2,
elevation: 3,
},
addText: {},
});
这是我的 task.js 代码，它是一个组件：
import React from 'react';
import {
View,
Text,
StyleSheet,
Dimensions,
Animated,
TouchableOpacity,
} from 'react-native';
import AppLoading from 'expo-app-loading';
import {
Poppins_100Thin,
Poppins_100Thin_Italic,
Poppins_200ExtraLight,
Poppins_200ExtraLight_Italic,
Poppins_300Light,
Poppins_300Light_Italic,
Poppins_400Regular,
Poppins_400Regular_Italic,
Poppins_500Medium,
Poppins_500Medium_Italic,
Poppins_600SemiBold,
Poppins_600SemiBold_Italic,
Poppins_700Bold,
Poppins_700Bold_Italic,
Poppins_800ExtraBold,
Poppins_800ExtraBold_Italic,
Poppins_900Black,
Poppins_900Black_Italic,
} from '@expo-google-fonts/poppins';
import { useFonts } from 'expo-font';
import Swipeable from 'react-native-gesture-handler/Swipeable';
const SCREEN_WIDTH = Dimensions.get('window').width;
const Task = (props) => {
let [fontsLoaded, error] = useFonts({
Poppins_100Thin,
Poppins_100Thin_Italic,
Poppins_200ExtraLight,
Poppins_200ExtraLight_Italic,
Poppins_300Light,
Poppins_300Light_Italic,
Poppins_400Regular,
Poppins_400Regular_Italic,
Poppins_500Medium,
Poppins_500Medium_Italic,
Poppins_600SemiBold,
Poppins_600SemiBold_Italic,
Poppins_700Bold,
Poppins_700Bold_Italic,
Poppins_800ExtraBold,
Poppins_800ExtraBold_Italic,
Poppins_900Black,
Poppins_900Black_Italic,
});
if (!fontsLoaded) {
return <AppLoading />;
}
const leftSwipe = (progress, dragX) => {
const scale = dragX.interpolate({
inputRange: [0, 100],
outputRange: [0, 1],
extrapolate: 'clamp',
});
return (
<TouchableOpacity onPress={props.handleDelete} activeOpacity={0.6}>
<View style={styles.deleteBox}>
<Animated.Text
style={{
transform: [{ scale: scale }],
color: '#fff',
fontFamily: 'Poppins_400Regular',
fontSize: 18,
}}>
Delete
</Animated.Text>
</View>
</TouchableOpacity>
);
};
return (
<Swipeable renderLeftActions={leftSwipe}>
<View style={styles.item}>
<View style={styles.itemLeft}>
<View style={styles.square}></View>
<Text style={styles.itemText}>{props.text}</Text>
</View>
<View style={styles.circular}></View>
</View>
</Swipeable>
);
};
const styles = StyleSheet.create({
item: {
backgroundColor: 'white',
padding: 15,
borderRadius: 10,
flexDirection: 'row',
alignItems: 'center',
justifyContent: 'space-between',
marginBottom: 20,
shadowColor: '#000',
shadowOffset: { width: 0, height: 1 },
shadowOpacity: 0.5,
shadowRadius: 2,
elevation: 3,
},
itemLeft: {
flexDirection: 'row',
alignItems: 'center',
flexWrap: 'wrap',
},
square: {
width: 24,
height: 24,
backgroundColor: '#55BCF6',
opacity: 0.5,
borderRadius: 5,
marginRight: 15,
},
itemText: {
maxWidth: '80%',
fontFamily: 'Poppins_400Regular',
},
circular: {
width: 12,
height: 12,
borderColor: '#55BCF6',
borderWidth: 2,
borderRadius: 5,
},
deleteBox: {
backgroundColor: 'red',
justifyContent: 'center',
alignItems: 'center',
width: 100,
height: 55,
borderRadius: 10,
shadowColor: '#000',
shadowOffset: { width: 0, height: 1 },
shadowOpacity: 0.5,
shadowRadius: 2,
elevation: 5,
},
});
export default Task;
由于 React 内部状态更新实现，在更新新状态之前更新异步存储 运行。建议在更新状态之前 运行 异步代码。
要解决此问题，请按如下方式重构您的代码：
handleAddTask= async ()=>{
Keyboard.dismiss()
const updatedTaskItems = [...this.state.taskItems,this.state.task]
await AsyncStorage.setItem('data',JSON.stringify(updatedTaskItem))
this.setState({taskItems:updatedTaskUtems,task:''})
}
我在 React Native 中遇到有关异步存储的问题。
当我在异步存储中设置项目，然后如果有 3 个我添加的任务时检索它，
只检索到其中两个
我会分享前后的照片
this is output before refreshing
this is the output after refreshing the app
这是我的app.js代码
import { StatusBar } from 'expo-status-bar';
import {
StyleSheet,
Text,
View,
KeyboardAvoidingView,
FlatList,
TextInput,
TouchableOpacity,
Keyboard,
} from 'react-native';
import React, { Component } from 'react';
import * as Font from 'expo-font';
import Task from './components/Task';
import AppLoading from 'expo-app-loading';
import AsyncStorage from '@react-native-async-storage/async-storage';
let customFonts = {
Poppins_SemiBold: require('./assets/Poppins-SemiBold.ttf'),
Poppins_Regular: require('./assets/Poppins-Regular.ttf'),
};
export default class App extends Component {
constructor(props) {
super(props);
this.state = {
task: '',
taskItems: [],
fontsLoaded: false,
};
}
async _loadFontsAsync() {
await Font.loadAsync(customFonts);
this.setState({ fontsLoaded: true });
}
componentDidMount() {
this._loadFontsAsync();
this._retrieveData()
}
_retrieveData = async () => {
try {
const value = await AsyncStorage.getItem('data');
if (value.length !== 2) {
// We have data!!
this.setState({taskItems:[...JSON.parse(value)]})
console.log(value);
}
} catch (error) {
// Error retrieving data
console.log(error)
}
};
handleAddTask=()=>{
Keyboard.dismiss()
this.setState({taskItems:[...this.state.taskItems,this.state.task]})
this.setState({task:''})
AsyncStorage.setItem('data',JSON.stringify(this.state.taskItems))
}
deleteItem=(index)=>{
try {
let arr = [...this.state.taskItems];
arr.splice(index, 1);
this.setState({taskItems:arr})
AsyncStorage.setItem('data',JSON.stringify(arr))
} catch (err) {
console.log(err);
}
}
render() {
if (!this.state.fontsLoaded) {
return <AppLoading />;
}
return (
<View style={styles.container}>
{/* Todays Tasks */}
<View style={styles.taskWrapper}>
<Text style={styles.sectionTitle}>Today's Tasks</Text>
<View style={styles.items}>
{/* This is where the tasks will go! */}
<FlatList
data={this.state.taskItems}
keyExtractor={(item) => item}
renderItem={({ item, index }) => (
<Task text={item} handleDelete={() => this.deleteItem(index)} />
)}
/>
</View>
</View>
{/* Write a Task */}
<KeyboardAvoidingView style={styles.writeTaskWrapper}>
<TextInput
style={styles.input}
placeholder={'Write A Task!'}
onChangeText={(text) => {
this.setState({ task: text });
}}
value={this.state.task}
/>
<TouchableOpacity
onPress={() => {
this.handleAddTask();
}}>
<View style={styles.addWrapper}>
<Text style={styles.addText}>+</Text>
</View>
</TouchableOpacity>
</KeyboardAvoidingView>
</View>
);
}
}
const styles = StyleSheet.create({
container: {
flex: 1,
backgroundColor: '#E8EAED',
},
taskWrapper: {
paddingTop: 80,
paddingHorizontal: 20,
},
sectionTitle: {
fontSize: 24,
backgroundColor: '#fff',
fontFamily: 'Poppins_SemiBold',
borderRadius: 10,
margin: 'auto',
width: 250,
height: 60,
textAlign: 'center',
shadowColor: '#000',
shadowOffset: { width: 0, height: 1 },
shadowOpacity: 0.2,
shadowRadius: 2,
elevation: 5,
paddingTop: 10,
},
items: {
marginTop: 30,
},
writeTaskWrapper: {
position: 'absolute',
bottom: 60,
width: '100%',
flexDirection: 'row',
justifyContent: 'space-around',
alignItems: 'center',
},
input: {
paddingVertical: 15,
paddingHorizontal: 15,
backgroundColor: '#fff',
borderRadius: 60,
width: 250,
fontFamily: 'Poppins_Regular',
shadowColor: '#000',
shadowOffset: { width: 0, height: 1 },
shadowOpacity: 0.5,
shadowRadius: 2,
elevation: 3,
},
addWrapper: {
width: 60,
height: 60,
backgroundColor: '#fff',
borderRadius: 60,
justifyContent: 'center',
alignItems: 'center',
shadowColor: '#000',
shadowOffset: { width: 0, height: 1 },
shadowOpacity: 0.5,
shadowRadius: 2,
elevation: 3,
},
addText: {},
});
这是我的 task.js 代码，它是一个组件：
import React from 'react';
import {
View,
Text,
StyleSheet,
Dimensions,
Animated,
TouchableOpacity,
} from 'react-native';
import AppLoading from 'expo-app-loading';
import {
Poppins_100Thin,
Poppins_100Thin_Italic,
Poppins_200ExtraLight,
Poppins_200ExtraLight_Italic,
Poppins_300Light,
Poppins_300Light_Italic,
Poppins_400Regular,
Poppins_400Regular_Italic,
Poppins_500Medium,
Poppins_500Medium_Italic,
Poppins_600SemiBold,
Poppins_600SemiBold_Italic,
Poppins_700Bold,
Poppins_700Bold_Italic,
Poppins_800ExtraBold,
Poppins_800ExtraBold_Italic,
Poppins_900Black,
Poppins_900Black_Italic,
} from '@expo-google-fonts/poppins';
import { useFonts } from 'expo-font';
import Swipeable from 'react-native-gesture-handler/Swipeable';
const SCREEN_WIDTH = Dimensions.get('window').width;
const Task = (props) => {
let [fontsLoaded, error] = useFonts({
Poppins_100Thin,
Poppins_100Thin_Italic,
Poppins_200ExtraLight,
Poppins_200ExtraLight_Italic,
Poppins_300Light,
Poppins_300Light_Italic,
Poppins_400Regular,
Poppins_400Regular_Italic,
Poppins_500Medium,
Poppins_500Medium_Italic,
Poppins_600SemiBold,
Poppins_600SemiBold_Italic,
Poppins_700Bold,
Poppins_700Bold_Italic,
Poppins_800ExtraBold,
Poppins_800ExtraBold_Italic,
Poppins_900Black,
Poppins_900Black_Italic,
});
if (!fontsLoaded) {
return <AppLoading />;
}
const leftSwipe = (progress, dragX) => {
const scale = dragX.interpolate({
inputRange: [0, 100],
outputRange: [0, 1],
extrapolate: 'clamp',
});
return (
<TouchableOpacity onPress={props.handleDelete} activeOpacity={0.6}>
<View style={styles.deleteBox}>
<Animated.Text
style={{
transform: [{ scale: scale }],
color: '#fff',
fontFamily: 'Poppins_400Regular',
fontSize: 18,
}}>
Delete
</Animated.Text>
</View>
</TouchableOpacity>
);
};
return (
<Swipeable renderLeftActions={leftSwipe}>
<View style={styles.item}>
<View style={styles.itemLeft}>
<View style={styles.square}></View>
<Text style={styles.itemText}>{props.text}</Text>
</View>
<View style={styles.circular}></View>
</View>
</Swipeable>
);
};
const styles = StyleSheet.create({
item: {
backgroundColor: 'white',
padding: 15,
borderRadius: 10,
flexDirection: 'row',
alignItems: 'center',
justifyContent: 'space-between',
marginBottom: 20,
shadowColor: '#000',
shadowOffset: { width: 0, height: 1 },
shadowOpacity: 0.5,
shadowRadius: 2,
elevation: 3,
},
itemLeft: {
flexDirection: 'row',
alignItems: 'center',
flexWrap: 'wrap',
},
square: {
width: 24,
height: 24,
backgroundColor: '#55BCF6',
opacity: 0.5,
borderRadius: 5,
marginRight: 15,
},
itemText: {
maxWidth: '80%',
fontFamily: 'Poppins_400Regular',
},
circular: {
width: 12,
height: 12,
borderColor: '#55BCF6',
borderWidth: 2,
borderRadius: 5,
},
deleteBox: {
backgroundColor: 'red',
justifyContent: 'center',
alignItems: 'center',
width: 100,
height: 55,
borderRadius: 10,
shadowColor: '#000',
shadowOffset: { width: 0, height: 1 },
shadowOpacity: 0.5,
shadowRadius: 2,
elevation: 5,
},
});
export default Task;
由于 React 内部状态更新实现，在更新新状态之前更新异步存储 运行。建议在更新状态之前 运行 异步代码。
要解决此问题，请按如下方式重构您的代码：
handleAddTask= async ()=>{
Keyboard.dismiss()
const updatedTaskItems = [...this.state.taskItems,this.state.task]
await AsyncStorage.setItem('data',JSON.stringify(updatedTaskItem))
this.setState({taskItems:updatedTaskUtems,task:''})
}