I'm having a trouble in a flatlist that a button increments the value but doesn't show if I don't refresh or hit ctrl-s after incrementing value. Basically I cannot see the value change without pressing ctrl-s or going to another page and returning to the same page.
<FlatList
data={store}
renderItem={({ item }) => {
return (
<View style={styles.itemCountView}>
<TouchableOpacity style={styles.up}
onPress={() => item.itemCount++}>
<MaterialIcons name="arrow-drop-up" size={36} color="#ddd"/>
</TouchableOpacity>
<Text style={styles.itemCountText}>{item.itemCount}</Text>
</View>
)
}}
/>
I can increment the value, if I save or go to another page and come back the value changes and i can see it but there must be a way to see it change.
Any help is appreciated
As per the Documentation
extraData: https://reactnative.dev/docs/flatlist#extradata
A marker property for telling the list to re-render (since it implements PureComponent). If any of your renderItem, Header, Footer, etc. functions depend on anything outside of the data prop, stick it here and treat it immutably.
I think you'r not saving the changes you doing, basically you need to update the the store variable each time you increment an item, something like:
<FlatList
data={store}
renderItem={({ item }) => {
return (
<View style={styles.itemCountView}>
<TouchableOpacity style={styles.up}
onPress={() => {
const newStoreData = [...store]
const itemIndex = newStoreData.findIndex(item)
const newItem = {...item,itemCount:item.itemCount ++}
newStoreData[itemIndex] = newItem
setStoreData(newStoreData) // state or redux?
}
}>
<MaterialIcons name="arrow-drop-up" size={36} color="#ddd"/>
</TouchableOpacity>
<Text style={styles.itemCountText}>{item.itemCount}</Text>
</View>
)
}}
/>
You can try this approach here:
import {useState} from 'react';
import { Text, View, FlatList, TouchableOpacity } from 'react-native';
const store = [{
itemCount: 1
},
{
itemCount: 2
},
{
itemCount: 3
}]
export default function App() {
return (
<View style={{
flex: 1,
padding: 140,
}}>
<FlatList
data={store}
renderItem={({ item }) => ( <Item item={item}/> )}
/>
</View>
);
}
const Item = ({item})=> {
const[count, setCount] = useState(item.itemCount);
return (
<View>
<TouchableOpacity
style={{
backgroundColor: 'black',
padding: 10,
margin: 10
}}
onPress={() => setCount(count+1)}>
<Text style={{
color: 'white'
}}>{count}</Text>
</TouchableOpacity>
</View>
)
}
This will set the state for each item in the Flatlist.
I want to pass the item (asset) from a Flastlist and present in a child screen.
But when I press the item, the parameter is null. I have to go back and press it again for the parameter to be set. And if I press a different item, the old item still lingers until I press the new item a second time.
I don't know if useEffect is the best way to do it. I am just trying different approaches but have not had any luck with useEffect, useFocusEffect, or none.
Parent with the Flastlist
export default function SitesScreen(props) {
const [sites, setSites] = useState(["Power Plant", "Paper Mill", "Plastic Injection"])
const [selectedItem, setSelectedItem] = useState(null)
const Item = ({ item, onPress }) => (
<TouchableOpacity onPress={onPress} style={[styles.item]} >
<Text style={styles.text}>{item}</Text>
</TouchableOpacity>
)
const renderItem = ({ item }) => {
return (
<View style={styles.itemContainer} >
<Item
item={item}
onPress={() => onItemSelected(item)}
/>
</View >
)
}
const onItemSelected = (item) => {
setSelectedItem(item)
props.navigation.navigate("Asset", { asset: selectedItem })
}
return (
<View style={styles.container}>
<CustomHeader title="Sites" navigation={props.navigation} isHome={true} ></CustomHeader>
<View style={styles.contentContainer}>
<View style={{ width: '90%', height: '50%', alignItems: 'center', bottom: -150 }} >
<FlatList
data={sites}
renderItem={renderItem}
keyExtractor={(item) => JSON.stringify(item)}
/>
</View>
</View>
</View>
)}
Child screen to present item
export default function SitesScreen(props) {
const [asset, setAsset] = useState('')
useEffect(() => {
setAsset(props.route.params.asset)
console.log(asset)
}, [])
return (
<View style={styles.container}>
<CustomHeader title="Asset" navigation={props.navigation} isHome={false} ></CustomHeader>
<View style={styles.contentContainer}>
<Text style={styles.text} >{asset}</Text>
<View style={{ width: '90%', height: '50%', alignItems: 'center', bottom: -150 }} >
</View>
</View>
</View>
)}
When you pass the selectedItem value as a parameter to the next screen, the new state set from setSelectedItem has not been applied to the component yet. Because the new state hasn't been applied, you are still passing the initial null value that was set for selectedItem. This happens because state values are used by functions based on their current closures.
See this StackOverflow post for a more detailed explanation about this problem.
Problem solved.
The parent screen needs to have the navigate action in the useEffect hook, and not in the onItemSelected function. That way it waits until the state has been changed before it navigates.
useEffect(() => {
if (selectedItem) {
props.navigation.navigate("Asset", { asset: selectedItem })
}
}, [selectedItem])
After upgrading to react-native 0.61 i get a lot of warnings like that:
VirtualizedLists should never be nested inside plain ScrollViews with the same orientation - use another VirtualizedList-backed container instead.
What is the other VirtualizedList-backed container that i should use, and why is it now advised not to use like that?
If someone's still looking for a suggestion to the problem that #Ponleu and #David Schilling have described here (regarding content that goes above the FlatList), then this is the approach I took:
<SafeAreaView style={{flex: 1}}>
<FlatList
data={data}
ListHeaderComponent={ContentThatGoesAboveTheFlatList}
ListFooterComponent={ContentThatGoesBelowTheFlatList} />
</SafeAreaView>
You can read more about this here: https://facebook.github.io/react-native/docs/flatlist#listheadercomponent
Hopefully it helps someone. :)
Just in case this helps someone, this is how I fixed the error in my case.
I had a FlatList nested inside a ScrollView:
render() {
return (
<ScrollView>
<Text>{'My Title'}</Text>
<FlatList
data={this.state.myData}
renderItem={({ item }) => {
return <p>{item.name}</p>;
}}
/>
{this.state.loading && <Text>{'Loading...'}</Text>}
</ScrollView>
);
}
and I got rid of the ScrollView by using the FlatList to render everything I needed, which got rid of the warning:
render() {
const getHeader = () => {
return <Text>{'My Title'}</Text>;
};
const getFooter = () => {
if (this.state.loading) {
return null;
}
return <Text>{'Loading...'}</Text>;
};
return (
<FlatList
data={this.state.myData}
renderItem={({ item }) => {
return <p>{item.name}</p>;
}}
ListHeaderComponent={getHeader}
ListFooterComponent={getFooter}
/>
);
}
The best way is to disable that warning because sometimes Flatlist need to be in ScrollView.
UPDATE RN V0.63 ABOVE
YellowBox is now changed and replace with LogBox
FUNCTIONAL
import React, { useEffect } from 'react';
import { LogBox } from 'react-native';
useEffect(() => {
LogBox.ignoreLogs(['VirtualizedLists should never be nested']);
}, [])
CLASS BASED
import React from 'react';
import { LogBox } from 'react-native';
componentDidMount() {
LogBox.ignoreLogs(['VirtualizedLists should never be nested']);
}
UPDATE RN V0.63 BELOW
FUNCTIONAL
import React, { useEffect } from 'react';
import { YellowBox } from 'react-native';
useEffect(() => {
YellowBox.ignoreWarnings(['VirtualizedLists should never be nested']);
}, [])
CLASS BASED
import React from 'react';
import { YellowBox } from 'react-native';
componentDidMount() {
YellowBox.ignoreWarnings(['VirtualizedLists should never be nested']);
}
Data
// dummy data array
const data = [
{id: 1, name: 'Tom'},
{id: 2, name: 'Jerry'},
]
Solution #1
You can make a custom component for that like this
const VirtualizedList = ({children}) => {
return (
<FlatList
data={[]}
keyExtractor={() => "key"}
renderItem={null}
ListHeaderComponent={
<>{children}</>
}
/>
)
}
then use this VirtualizedList as parent component:
...
return (
<VirtualizedList>
<FlatList
data={data}
keyExtractor={(item, index) => item.id + index.toString()}
renderItem={_renderItem}
/>
<AnyComponent/>
</VirtualizedList>
)
Solution #2
If you use FlatList inside the ScrollView it gives warning which is annoying, so you can use array's map property, like this -
NOTE: It is not recommended way to show list. If you have small amount of that then you can use it that's totally fine, but if you want to show a list which get data from api and have lot's of data then you can go with other solutions. if you use map with large data then it affect your app performance
<ScrollView>
{data.map((item, index) => (
<View key={index}>
<Text>{item.name}</Text>
</View>
))}
</ScrollView>
Solution #3
if you make your FlatList horizontal (as per your need) then also warning will disappear
<ScrollView>
<FlatList
data={data}
keyExtractor={(item, index) => item.id + index.toString()}
horizontal={true}
/>
</ScrollView>
Solution #4
you can add header and footer component
In ListHeaderComponent and ListFooterComponent you can add any component so you don't need parent ScrollView
<FlatList
data={data}
keyExtractor={(item, index) => item.id + index.toString()}
ListHeaderComponent={headerComponent}
ListFooterComponent={footerComponent}
ListEmptyComponent={emptyComponent}
ItemSeparatorComponent={separator}
/>
// List components
const headerComponent = () => (
<View>
<Header/>
<Any/>
</View>
)
const footerComponent = () => (
<View>
<Footer/>
<Any/>
</View>
)
const emptyComponent = () => (
<View>
<EmptyView/>
<Any/>
</View>
)
const separator = () => (
<View style={{height: 0.8, width: '100%', backgroundColor: '#fff'}} />
)
The warning appears because ScrollView and FlatList share the same logic, if FlatList run inside ScrollView, it's duplicated
By the way SafeAreaView doesn't work for me, the only way to solve is
<ScrollView>
{data.map((item, index) => {
...your code
}}
</ScrollView>
The error disappears
Looking at the examples in docs I've changed container from:
<ScrollView>
<FlatList ... />
</ScrollView>
to:
<SafeAreaView style={{flex: 1}}>
<FlatList ... />
</SafeAreaView>
and all those warnings disappeared.
In my case, I needed to have FlatLists nested in a ScrollView because I am using react-native-draggable-flatlist to move ingredients and steps around in a recipe.
If we read the warning properly, it says that we should use another VirtualizedList-backed container to nest our child FlatList in. What I did is:
/* outside the component */
const emptyArry = []
/* render */
<FlatList
scrollEnabled={false}
horizontal
data={emptyArray}
ListEmptyComponent=(<DraggableList />)
/>
No more warning, and I think this is the pattern recommended by the warning.
<ScrollView horizontal={false} style={{width: '100%', height: '100%'}}>
<ScrollView horizontal={true} style={{width: '100%', height: '100%'}}>
<FlatList ... />
</ScrollView>
</ScrollView>
Below code works perfectly for me to disable annoying error:
VirtualizedLists should never be nested inside plain ScrollViews with the same orientation because it can break windowing and other functionality - use another VirtualizedList-backed container instead.
React Native 0.68.2
<ScrollView horizontal={false} style={{flex: 1}}>
<ScrollView
horizontal={true}
contentContainerStyle={{width: '100%', height: '100%'}}>
<FlatList ... />
</ScrollView>
</ScrollView>
I tried some ways to solve this, including ListHeaderComponent or ListFooterComponent, but it all didn't fit for me.
layout I wanted to achieve is like this, and I wanted to get scrolled in once.
<ScrollView>
<View>I'm the first view</View>
<View>I'm the second view</View>
<MyFlatList />
</ScrollView>
First I want to say thanks to this issue and comments, which gave me bunch of ideas.
I was thinking of ListHeaderComponent places above the Flatlist, but since my Flatlist's direction was column, the header I wanted to place went on the left of the Flatlist :(
Then I had to try on VirtualizedList-backed thing. I just tried to pack all components in VirtualizedList, where renderItems gives index and there I could pass components conditionally to renderItems.
I could have worked this with Flatlist, but I haven't tried yet.
Finally it looks like this.
<View>
<Virtualizedlist
data={[]}
initialNumToRender={1}
renderItem={(props)=>{
props.index===0 ? (1st view here) : props.index===1 ? (2nd view here) : (my flatlist)
}}
keyExtractor={item => item.key}
getItemCount={2}
getItem={ (data, index) => {
return {
id: Math.random().toString(12).substring(0),
}
}}
/>
</View>
(inside which lazyly renders↓)
<View>I'm the first view</View>
<View>I'm the second view</View>
<MyFlatList />
and of course able to scroll the whole screen.
As #Brahim stated above, setting the horizontal property to true seem to resolve the issues for a FlatList embedded in a ScrollView.
So I faced the same problem while using a picker-based component inside <ScrollView> and the one thing that helped me solve the problem was adding
keyboardShouldPersistTaps={true} inside the <ScrollView> as a prop.
This is my code snippet.
<ScrollView keyboardShouldPersistTaps={true}>
<SelectionDD studentstatus={studentStatus}/>
<SearchableDD collegeNames={collegeNames} placeholder='University'/>
</ScrollView>
I have two Flatlist; each of them has many Item also has a feature to collapse and expand.
Because of that, I can't use SafeAreaView.
I saw another solution and found a new way.
I define one Flatlist in the core component ( without Scrollview) and render each Flatlist with a map function inside ListHeaderComponent and ListFooterComponent.
<View style={{flex: 1}}>
<FlatList
style={{backgroundColor: 'white'}}
refreshing={loading}
onRefresh={() => sample()}
ListHeaderComponent = {
<View>
{collapse/expandComponent}
{this.state.sample1&& content1.map((item, index) => this.renderList1(item,index))}
</View>
}
ListFooterComponent = {
<View>
{collapse/expandComponent}
{this.state.sample2 && content2.map((item, index) => this.renderlist2(item,index))}
</View>
}
/>
</View>
In my opinion i can use map instead of FlatList. But in my case i wan't to show large list. Not using FlatList may cause performance issue. so i used this to suppress warning https://github.com/GeekyAnts/NativeBase/issues/2947#issuecomment-549210509
Without hiding YellowBox you still can implement scroollable view inside scrollable view. You can use this library. It replace the default Scrollview from React Native.
This may help someone down the line, be sure you to check how your components are nested. Removing the ScrollView from the top component fixed the issue.
I ran into this issue because I had two components nested like this essentially:
Component 1
<ScrollView>
<OtherStuff />
<ListComponent />
</ScrollView>
My second component 'ListComponent' had a FlatList already wrapped with SafeAreaView.
<SafeAreaView style={styles.container}>
<FlatList
data={todoData}
renderItem={renderItem}
ItemSeparatorComponent={() => <View style={styles.separator} />}
keyExtractor={item => item.id.toString()}
/>
</SafeAreaView>
In the end I replaced the ScrollView from the first component with a View instead.
Use flatList like this ListHeaderComponent and ListFooterComponent:
<FlatList ListHeaderComponent={
<ScrollView
style={styles.yourstyle}
showsVerticalScrollIndicator={false}
>
<View style={styles.yourstyle}>
</View>
</ScrollView>
}
data={this.state.images}
renderItem={({ item, index }) => {
return (
<View
style={styles.yourstyle}
>
<Image
source={{
uri: item,
}}
style={styles.yourstyle}
resizeMode={"contain"}
/>
<Text
numberOfLines={2}
ellipsizeMode="tail"
style={styles.yourstyle}
>
{item.name}
</Text>
</View>
);
}}
keyExtractor={({ name }, index) => index.toString()}
ListFooterComponent={
<View style={styles.yourstyle}></View>
}
/>
If you use ScrollView and FlatList together you'll get inconsistent scroll behaviour.
So just remove ScrollView and use FlatList in a View.
<View flex={1}>
<FlatList
data={list}
renderItem={({ item }) => this.renderItem(item) }
keyExtractor={item => item.id}
/>
</View>
import React from 'react';
import { FlatList, ScrollViewProps } from 'react-native';
export const ScrollView: React.FC<ScrollViewProps> = props => {
return (
<FlatList
{...props}
data={[]}
renderItem={() => null}
ListHeaderComponent={() => (
<React.Fragment>{props.children}</React.Fragment>
)}
ListEmptyComponent={null}
keyExtractor={() => 'blank'}
/>
);
};
This will essentially work exactly like a ScrollView except without this error.
I was having this issue using a scrollview as parent view, and nesting a SelectBox from react-native-multi-selectbox package. I was able to solve this by adding listOptionProps={{nestedScrollEnabled: true}} like this:
<ScrollView>
<SelectBox
label="Select single"
options={serverData}
listOptionProps={{nestedScrollEnabled: true}}
value={input.elementSelected}
onChange={event =>
inputHandlerLang('elementSelected', event, key)
}
hideInputFilter={false}
/>
</ScrollView>
the error still present but scrolling within SelectBox works as well as within the parent scrollview. I also do have to suppress the error with LogBox. I don't know if there are any drawbacks to this but I'll try to test this more.
Update 1: this used to work in v0.68.2, but since I updated to patch v0.68.5, the warning became an error.
You have to remove ScrollView and enable scroll from FlatList using the property scrollEnabled={true}, you can place the other views inside ListHeaderComponent and ListFooterComponent
<View flex={1}>
<FlatList
data={data}
scrollEnabled={true}
showsVerticalScrollIndicator={false}
renderItem={({ item }) => (
<Text>{item.label}</Text>
)}
keyExtractor={item => item.id}
ListHeaderComponent={() => (
<Text>Title</Text>
)}
ListFooterComponent={() => (
<Text>Footer</Text>
)}
/>
</View>
Actually as I know, using nested VirtualizedLists, caused always performance issues, just the warning to that issue is new. I tried everything I found on the internet, non of them helped. I use now ScrollView or when you just have a normall View with maxHeight then you will be able to scroll if the content-height is bigger then the maxHeight of you View.
So:
<ScrollView>
{items.map((item, index) =>
<YourComponent key={index} item={item} />
)}
</ScrollView>
Or just:
<View style={{maxHeight: MAX_HEIGHT}}>
{items.map((item, index) =>
<YourComponent key={index} item={item} />
)}
</View>
This error disappeared because of using FlatList inside ScrollView. You can write like the following code.
<SafeAreaView style={styles.container}>
<View style={styles.container}>
<View>
<Header />
</View>
{(list.length == 0) &&
<View style={{flex:1, margin: 15}}>
<Text style={{textAlign: 'center'}}>No peripherals</Text>
</View>
}
<FlatList
data={list}
renderItem={({ item }) => this.renderItem(item) }
keyExtractor={item => item.id}
/>
</View>
</SafeAreaView>
You can add horizontal=True and contentContainerStyle={{ width: '100%' }} to the ScrollView parent.
<ScrollView
style={styles.collaborators}
contentContainerStyle={{ width: '100%' }} <--
horizontal <--
>
<FlatList
data={list?.slice(0, 10) || []}
keyExtractor={item => item.cc}
ItemSeparatorComponent={Separator}
renderItem={({ item }) => (
<Collaborator name={item.name} cc={item.cc} />
)}
/>
</ScrollView>
This worked for me (as a bit of a hack). Use a FlatList with empty data and null renderItem props instead of using a ScrollView
const emptyData = [];
const renderNullItem = () => null;
const App = () => {
const ListFooterComponent = (
<FlatList ... />
);
return (
<SafeAreaView>
<FlatList
data={emptyData}
renderItem={renderNullItem}
ListFooterComponent={ListFooterComponent}
/>
</SafeAreaView>
);
};
I had the same issue, and just got rid of it by removing the ScrollView around the FlatList. Because by default FlatList provides Scroll Functionality based on the length of content that it renders. 😊
i'm new in react native and i need your help
i want to give border-bottom to pressed item of horizontal flatlist and border-bottom of Previous item disappear,
now i can give border to new pressed item but i cant remove previous item border
how can i achive this?
enter image description here
these are my Category_style code
state = {
isModalVisible: false,
Index : 0
}
_toggleModal = (index) => {
this.setState({isModalVisible: !this.state.isModalVisible});
this.setState({Index : index});
}
renderProduct(item) {
return <Sub_Categories_FlatList_style name={item.title} icon={item.icon}/>
}
renderSeparator = () => (
<View
style={{
backgroundColor: '#d2d2d2',
height: 0.5,
}}
/>
)
render() {
const {title, index} = this.props;
return (
<View style={pStyles.container}>
<TouchableHighlight onPress={() => this._toggleModal(index)}
style={(index === this.state.Index) ? pStyles.border_bottom : pStyles.no_border_bottom}>
<Text style={pStyles.title}>{title}</Text>
</TouchableHighlight>
<Modal isVisible={this.state.isModalVisible} animationType={'slide'}>
<TouchableOpacity onPress={() => this._toggleModal(index)} style={pStyles.T_opacity}
activeOpacity={.7}>
<Image source={require('./../pictures/x_icon.png')}
style={pStyles.close_image}/>
</TouchableOpacity>
<View style={pStyles.in_modal_view}>
<Text style={pStyles.modal_header_text}>{title}</Text>
<FlatList
data={this.props.subCategory}
renderItem={({item}) => this.renderProduct(item)}
ItemSeparatorComponent={this.renderSeparator}
keyExtractor={(item, index) => index}/>
</View>
</Modal>
</View>
and these are my Category code
static navigationOptions = {
headerStyle: {
backgroundColor: '#4caf50'
},
headerTitle: <Text style={Category_in_style.headerTitleStyle}>Category</Text>
}
renderCategory(item, index) {
return <Category_style title={item.title} index={index} subCategory={item.sub_category}/>
}
renderProduct(item) {
return <Product_style image={item.imageUrl} title={item.title} price={item.price}/>
}
render() {
return (
<View style={{backgroundColor: 'white'}}>
<FlatList style={styles.first_flat}
horizontal
data={this.state.main_categories}
renderItem={({item, index})=> this.renderCategory(item, index)}
keyExtractor={(item, index) => index}/>
<PTRView style={{backgroundColor: '#f1f1f1'}}>
<FlatList style={[{marginTop: 10}, {marginBottom: 50}]}
data={this.state.articles}
renderItem={({item}) => this.renderProduct(item)}
keyExtractor={(item, index) => index}
numColumns={2}/>
</PTRView>
</View>
There may be multiple ways of doing this but I prefer having the parent decide which component is clicked.
So what I suggest is in your renderProduct the item object also has an index which you can pass to your Sub_Categories_FlatList_style and also pass a function to it which basically updates a variable whenever the item is clicked.
Then when you render the list item simply check if it's index matches the currently selected index and then style it accordingly.
Sorry if this seems a bit vague but I'm eyeballing this since I'm at work but I'll be more than happy to answer any follow ups.