Javascript Can';你不能立即更新状态吗?
我有两个函数,第一个我得到所有订单,第二个我得到所有被拒绝的订单 所以在第一个函数中,我根据第二个函数状态更新状态 而且效果很好 但是当我从Firebase控制台删除一个项目时,我无法立即看到更新,尽管我使用了Javascript Can';你不能立即更新状态吗?,javascript,reactjs,react-native,firebase-realtime-database,Javascript,Reactjs,React Native,Firebase Realtime Database,我有两个函数,第一个我得到所有订单,第二个我得到所有被拒绝的订单 所以在第一个函数中,我根据第二个函数状态更新状态 而且效果很好 但是当我从Firebase控制台删除一个项目时,我无法立即看到更新,尽管我使用了on(“value”,()=>{}) 那我怎么处理呢 警告 无法对未安装的组件执行React状态更新。这是 无操作,但表示应用程序内存泄漏 结构阵列 let ordersArray = [ {"snapshotKey":"-awdawadsdwwd","username":"Joe"
on(“value”,()=>{})
那我怎么处理呢
警告
无法对未安装的组件执行React状态更新。这是
无操作,但表示应用程序内存泄漏
结构阵列
let ordersArray = [
{"snapshotKey":"-awdawadsdwwd","username":"Joe"},
{"snapshotKey":"-badsdasdad","username":"Annna"},
{"snapshotKey":"-dasQwaddas","username":"lee"}
]
let rejectedOrders = ["-awdawadsdwwd","-dasQwaddas"]
陈述
this.state = {
orders: [],
rejectedOrders: [],
};
componentDidMount() {
try {
this.getRejectedOrders();
this.fetchOrders();
} catch (err) {
console.log('error', err);
}
}
第一功能
//Get all orders from DB
fetchOrders = async () => {
const {serviceName} = this.state;
let uid = auth().currentUser.uid;
const serviceStorage = await AsyncStorage.getItem('service');
this.setState({serviceStorage});
database()
.ref(`Providers/CategoriesOrders/${serviceName || serviceStorage}`)
.on('value', snapshot => {
let orderArr = [];
snapshot.forEach(childSnapshot => {
orderArr.push({
snapshotKey: childSnapshot.key,
username: childSnapshot.val().username,
});
});
this.setState(prevState => ({
orders: orderArr.filter(
order =>
!prevState.rejectedOrders.some(key => order.snapshotKey === key),
),
loading: false,
}));
});
};
第二功能
// get an array of rejected orders
getRejectedOrders = () => {
let uid = auth().currentUser.uid;
const ref = database().ref(`Providers/users/${uid}`);
ref.on('value', snapshot => {
let rejectedOrders = snapshot.val().rejectedOrders;
this.setState({rejectedOrders});
});
};
JSX
render(){
返回(
);
}
组成部分
const OrdersList = props => {
return (
<View style={styles.container}>
<FlatList
showsVerticalScrollIndicator={false}
data={props.data}
extraData={props.extraData}
ListEmptyComponent={<EmptyList />}
keyExtractor={(item, index) => index.toString()}
legacyImplementation={true}
contentContainerStyle={{
flexGrow: 1.2,
}}
renderItem={({item}) => {
return (
<TouchableOpacity
onPress={() =>
props.navigation.navigate(props.screenName, {
username: item.username,
snapshotKey: item.snapshotKey,
})
}
>
<View>
<Icon name="person" color="#AEACAC" size={20} />
<Text> {item.username}</Text>
</View>
</TouchableOpacity>
);
}}
/>
</View>
);
};
export default withNavigation(OrdersList);
const OrdersList=props=>{
返回(
index.toString()}
legacyImplementation={true}
内容容器样式={{
flexGrow:1.2,
}}
renderItem={({item})=>{
返回(
props.navigation.navigate(props.screenName{
用户名:item.username,
snapshotKey:item.snapshotKey,
})
}
>
{item.username}
);
}}
/>
);
};
使用导航导出默认值(订单列表);
我认为OrdersList组件存在问题,因为当我在每个函数“fetchOrders()/getRejectedOrders()”内的setState之后在回调中记录状态时,我得到的是新的被拒绝订单,而不是fetchOrders()内的订单
尽管
“当我向拒绝订单数组添加/删除数据时,这意味着getRejectedOrders()只会更改,但fetchOrders()不会更改,因为它与这些内容不相关。它在第一次获得所有订单,然后根据某些内容对其进行筛选,而这些订单没有更改,所以为什么要更新!”
编辑~1
fetchOrders = async () => {
const {rejectedOrders, serviceName} = this.state;
let uid = auth().currentUser.uid;
const serviceStorage = await AsyncStorage.getItem('service');
this.setState({serviceStorage});
// await this.getRejectedOrders();
database()
.ref(`Providers/CategoriesOrders/${serviceName || serviceStorage}`)
.on('value', snapshot => {
let orderArr = [];
snapshot.forEach(childSnapshot => {
orderArr.push({
snapshotKey: childSnapshot.key,
username: childSnapshot.val().username,
});
});
this.setState(
prevState => ({
orders: orderArr.filter(
order =>
!prevState.rejectedOrders.some(
key => order.snapshotKey === key,
),
),
loading: false,
}),
() => console.log(this.state.orders), // I don't git anything if i add or delete rejected orders
);
console.log(orderArr); // I don't git anything if i add or delete rejected orders
});
};
getRejectedOrders = async () => {
let uid = auth().currentUser.uid;
database()
.ref(`Providers/users/${uid}`)
.on('value', snapshot => {
let rejectedOrders = snapshot.val().rejectedOrders;
this.setState({rejectedOrders}, () =>
console.log(this.state.rejectedOrders), // here's i got every single time i add or delete item i can see it in console log
);
});
};
<OrdersList
data={this.state.orders}
extraData={this.state.orders.length} // i add it but it's not effected
screenName="OrderHomeDetails"
/>
fetchOrders=async()=>{
const{rejectedOrders,serviceName}=this.state;
让uid=auth().currentUser.uid;
const serviceStorage=await AsyncStorage.getItem('service');
this.setState({serviceStorage});
//等待此消息。getRejectedOrders();
数据库()
.ref(`Providers/CategoriesOrders/${serviceName | | serviceStorage}`)
.on('value',快照=>{
设orderArr=[];
snapshot.forEach(childSnapshot=>{
订单推送({
snapshotKey:childSnapshot.key,
用户名:childSnapshot.val().username,
});
});
这是我的国家(
prevState=>({
订单:orderArr.filter(
订单=>
!prevState.rejectedOrders.some(
key=>order.snapshotKey===key,
),
),
加载:false,
}),
()=>console.log(this.state.orders),//如果我添加或删除被拒绝的订单,我不会git任何东西
);
console.log(orderArr);//如果我添加或删除被拒绝的订单,我不会git任何东西
});
};
getRejectedOrders=async()=>{
让uid=auth().currentUser.uid;
数据库()
.ref(`Providers/users/${uid}`)
.on('value',快照=>{
让rejectedOrders=snapshot.val().rejectedOrders;
this.setState({rejectedOrders},()=>
log(this.state.rejectedOrders),//这是我每次添加或删除项时都能在控制台日志中看到的内容
);
});
};
当使用setState时,可以使用flag isMounted进行检查。关于问题状态不立即更新,您可以使用ref.current查看更改后立即更新。您应该在拒绝订单
更新时更新订单。此外,请记住取消录制侦听器以避免内存泄漏
constructor(props) {
super(props);
this.allOrders = [];
this.rejectedOrders = [];
this.state = {
orders: [],
}
}
componentWillUnmount() {
database()
.ref(`Providers/CategoriesOrders/${serviceName || serviceStorage}`)
.off('value', this.ordersCallback);
database()
.ref(`Providers/users/${uid}`)
.off('value', this.rejectedOrderCallback);
}
fetchOrders = async () => {
...
database()
.ref(`Providers/CategoriesOrders/${serviceName || serviceStorage}`)
.on('value', this.ordersCallback);
};
getRejectedOrders = async () => {
let uid = auth().currentUser.uid;
database()
.ref(`Providers/users/${uid}`)
.on('value', this.rejectedOrderCallback);
};
ordersCallback = (snapshot) => {
let orderArr = [];
snapshot.forEach(childSnapshot => {
orderArr.push({
snapshotKey: childSnapshot.key,
username: childSnapshot.val().username,
});
});
this.allOrders = orderArr;
this.updateData()
}
rejectedOrderCallback = (snapshot) => {
this.rejectedOrders = snapshot.val().rejectedOrders;
this.updateData();
}
updateData() {
const orders = this.allOrders.filter(order => this.rejectedOrders.some(key => order.snapshotKey === key));
this.setState({ orders });
}
您如何在UI上呈现订单?你能显示JSX吗?再次检查@anandudavia我认为keydextractor={(item,index)=>index.toString()}
是问题所在。尝试将其更改为keydractor={()=>Math.random()}
。如果有效,则意味着键
每次都是相同的,这就是列表未更新的原因,您可能想找到一个适当的函数,从项中提取key
。遗憾的是,我遇到了以下错误失败的子上下文类型:提供给“CellRenderer”的类型为“number”的无效子上下文“virtualizedCell.cellKey”,应为“string”。
尝试:keyExtractor={()=>Math.random().toString()}
感谢您的回复,但我有两个错误第一个无法读取未定义的属性“forEach”
2-警告:列表中的每个孩子都应该有一个唯一的“key”道具。
错误1,您需要更新自己,当您从数据库获取数据时,轮到您准备数据了。错误2,FlatList
需要每个项目都有一个唯一的id,默认情况下,它将从每个项目获得id
字段。如果您的订单项没有id
,则需要在keydextractor={order=>order.}
中指定一个唯一的值,谢谢您1-但是当我记录快照时,我可以在我的日志中看到所有订单!在刷新应用程序两次或两次以上后,它工作正常,为什么!这是一个很好的方法,但我有一些Q,在orderscalback()
中,您调用this.updateData(this.allOrders)
“带参数”,但在rejectedOrdersCallback()
中,您没有将任何参数传递给this.updateData()
为什么?它不会影响内存,updateData
只需准备从this.allOrders
和this.rejectedOrders
显示的数据即可。
constructor(props) {
super(props);
this.allOrders = [];
this.rejectedOrders = [];
this.state = {
orders: [],
}
}
componentWillUnmount() {
database()
.ref(`Providers/CategoriesOrders/${serviceName || serviceStorage}`)
.off('value', this.ordersCallback);
database()
.ref(`Providers/users/${uid}`)
.off('value', this.rejectedOrderCallback);
}
fetchOrders = async () => {
...
database()
.ref(`Providers/CategoriesOrders/${serviceName || serviceStorage}`)
.on('value', this.ordersCallback);
};
getRejectedOrders = async () => {
let uid = auth().currentUser.uid;
database()
.ref(`Providers/users/${uid}`)
.on('value', this.rejectedOrderCallback);
};
ordersCallback = (snapshot) => {
let orderArr = [];
snapshot.forEach(childSnapshot => {
orderArr.push({
snapshotKey: childSnapshot.key,
username: childSnapshot.val().username,
});
});
this.allOrders = orderArr;
this.updateData()
}
rejectedOrderCallback = (snapshot) => {
this.rejectedOrders = snapshot.val().rejectedOrders;
this.updateData();
}
updateData() {
const orders = this.allOrders.filter(order => this.rejectedOrders.some(key => order.snapshotKey === key));
this.setState({ orders });
}