I want to make a fetch request inside renderItem's componentDidMount method every time the list is refreshed, but the FlatList calls the lifecycle methods only once.
The list
<FlatList data={this.state.dataSource}
renderItem={({item}) => <ListItem imageHref={item.imageHref} />}
keyExtractor={(item, index) => index.toString()}
refreshing={this.state.refreshing}
onRefresh={/* Fetching data from JSON and updating dataSource[] */} />
Inside ListItem component:
render() {
return <Image source={this.state.imageSource} />
}
componentDidMount() {
fetch(this.props.imageHref)
.then(response => {
if(response.status !== 200)
this.setState({imageSource: require('../assets/default-image.png')
else
this.setState({imageSource: {uri: this.props.imageHref}});
}
});
}
I tried calling fetch inside render method but that didn't work either.
I basically want the imageSource to update every time the list is refreshed. Please help.
Because of that ListItem was not change. You have to fetch new icon in onRefresh and pass it into ListItem then all data will be changed when ListView will refresh... if you want to do it inside ListItem you need some interaction with that specific item, for example, some button and if user press it fetch and change icon
i didn't know when your list refreshed , but you can try this this.forceUpdate() you can learn more here force component to re render
Related
When I use onEndReached function in FlatList, it gets called automatically.
Below is the link of this issue.
Link
Is there a solution available for it or any alternative in iOS?
Edited:
Below is the code I tried but this doesn't seems to work.
constructor(props){
super(props);
this.state = {
flatListReady:false
}
}
loadMore(){
if(!this.state.flatListReady){
return null;
}
else{
alert("End Reached")
}
}
_scrolled(){
this.setState({flatListReady:true});
}
render() {
return (
<Layout style={{ flex: 1 }}>
<FlatList
data={listData}
renderItem={({item}) => this._renderItem(item)}
keyExtractor={(item, index) => item.key}
onEndReached={() => this.loadMore()}
onEndReachedThreshold={0.5}
onScroll={() => this._scrolled()}
/>
</Layout>
Try this,
onEndReachedThreshold={0.5}
onEndReached={({ distanceFromEnd }) => {
if(distanceFromEnd >= 0) {
//Call pagination function
}
}}
Sometimes things don't work like they are supposed to, at the end of the day it's not native code where, so may the order of your components or the fact that the Flatlist is encapsulated in a component that is not intended to be, or there is some property should be passed to the Flatlist component itself to activate the onEndReached callback properly.
I've faced this myself, and I didn't know what to do to make it work properly.
A beautiful workaround is derived from the fact the Flatlist inherits ScorllView properties. so you could use the onScroll property to detect if the end has reached or not.
<FlatList
data={this.props.dashboard.toPreviewComplaints}
onScroll={({nativeEvent})=>{
//console.log(nativeEvent);
if(!this.scrollToEndNotified && this.isCloseToBottom(nativeEvent)){
this.scrollToEndNotified = true;
this.loadMoreData();
}
}}
/>
this.scrollToEndNotified is used as a flag not to abuse the call to the loadMore endpoint
isCloseToBottom({layoutMeasurement, contentOffset, contentSize}){
return layoutMeasurement.height + contentOffset.y >= contentSize.height - 100;
}
So whenever it succeed in the isCloseToBottom call it means that you have reached the end of the list, so you can call the loadMoreData function
handle this function very carefully,
endReached=()=>{
//take care of ES6 Fat arrow function and trigger your conditions properly with current state and new state data or current state with new Props.
Based on those conditions only, you need to trigger the other API call
}
<FlatList data={this.state.data}
extraData={this.state.load}
renderItem={this.renderCard}
keyExtractor={item => item.fundRequestId}
onEndReached={this.endReached}
onEndReachedThreshold={.7}
ListFooterComponent={this.renderFooter}
/>
I am building a simple horizontal React Native FlatList with paging enabled:
<FlatList
horizontal={true}
pagingEnabled={true}
data={...some data...}
renderItem={({item}) => {...some rendering...}}
onViewableItemsChanged={(info) => {... handling ...}}
/>
I would like to get called back only after a new page in the list has been made visible. The behavior that I am seeking is that, as the user swipes the list left and right, the list will page through the items and I want the callback to fire once with the visible items.
The onViewableItemsChanged props is called on every change in visible items which is not what I am looking for, unless I keep track on which page the items belong to.
I am looking for a onViewablePageChanged type of callback.
Any ideas on how to achieve this?
The solution I used was to track the viewable items against the overall list of items to determine the "page" number of viewable items.
By using pagingEnabled, the list will only show pages.
However onViewableItemsChanged is called back on every changes to the viewable items. By comparing the viewable items againts the list of items, one can figure out on which "page" the FlatList is.
This requires that one knows how many items can be displayed in the view. Either calculated based on layout or set in the View and FlatList rendering.
Here's an example:
onViewableItemsChanged = ({viewableItems}) => {
// Get the first viewable item
const firstViewableItem = viewableItems[0].key;
// Get its index into the items
const index = this.state.items.findIndex(item => item.key === firstViewableItem);
// If the index is a multiple of the number of items displayable on the screen
// by checking for a reminder on the modulo operation
if ((index % NB_ITEMS_SCREEN) === 0) {
// get page
const currentPage = index / NB_ITEMS_SCREEN;
if (currentPage !== this.state.currentPage) {
// Do something and update currentPage in this.state
}
}
}
<FlatList
data={this.state.items}
horizontal={true}
pagingEnabled={true}
renderItem={({ item }) => <Text>{item.key}</Text>}
onViewableItemsChanged={this.onViewableItemsChanged}
/>
See this snack
https://snack.expo.io/#visto9259/flatlist-onviewableitemschanged-example
You can achieve visible items by using below code. Try this.
//Method to invoke when item change
onViewableItemsChanged = ({ viewableItems, changed }) => {
console.log("Visible items are", viewableItems);
console.log("Changed in this iteration", changed);
}
render () => {
return (
...
<FlatList
horizontal={true}
pagingEnabled={true}
data={...some data...}
renderItem={({item}) => {...some rendering...}}
onViewableItemsChanged={this.onViewableItemsChanged }
viewabilityConfig={{
itemVisiblePercentThreshold: 50
}}
/>
....
)}
I'm stuck for weeks on this problem that I can't solve. I have been through a lot of different solution and none of them is working..
Let-s say I have component A and component B
Component A : contains a flatlist, when click on one item leads me to component B.
Component B: contains details of component A items, when clicking on a button update data, data that component A is using in state current, which make the clicked items turn to orange. I would like when hitting back button to update those data in component A and actually have the clicked items in orange, right now nothing is happening..
Component A :
async interventionList(){
const planningList = await getInterventionList(this.state.userToken, '2019-02-27', '2019-02-27');
this.setState({list: planningList});
}
renderItem = ({ item }) => (
<View>
<TouchableHighlight onPress={
() => this.props.navigation.navigate('InterventionStart', { getIntervention: () => this.interventionsList() })}>
<View style={[styles.block, this.state.current !== null && this.state.current.remoteInterventionId === item.num ? styles.began : styles.notbegan]}>
<Text> {SomeData} <Text>
</View>
</View>
</TouchableHighlight>
</View>
)
Component B :
componentWillUnmount() {
this.props.navigation.state.params.getIntervention();
}
But nothing happens. I tried to console log, to see if those functions where called after clickin on back button and they are... So I don't understand what I am doing wrong or is it not the way to do this at all ?
You can use willFocus method of react-navigation
in your componentDidMount or in your constructor
this.willFocus = this.props.navigation.addListener('willFocus', () => {
this.interventionList();
});
It will call your interventionList method whenever your component is about to be focused. Make sure you remove the listener on your componentWillUnmount
this.willFocus.remove();
For reference
https://reactnavigation.org/docs/en/navigation-events.html
I am trying to toggle ios Switch in react native. But the switch comes back to initial position as soon as I change it.
What I have:
class ABC extends Component {
constructor(props) {
super(props)
this.state = {
obj: []
}
}
fetch(){
// fetch something from remote server, set it to state object array
}
setStatus(id, value){
var temp = [...this.state.obj]
temp.map((t) => {
if (t.id == id) {
t.flag = value
}
})
this.setState({ obj: temp })
}
render() {
return (
<View>
<FlatList
data={this.state.obj}
renderItem={({ item }) =>
<View>
<Text>{item.name}</Text>
<Switch
onValueChange={(val) => this.setStatus(item.id, val)}
value={item.flag}
/>
</View>
}
keyExtractor={({ id }, index) => id.toString()}
/>
</View>
);
}
}
I logged the before and after value of obj state and they seem to update. Should the FlatList be rendered again (like a web page refresh) ? Or is there something I am missing ? Searched SO for answers, couldn't find my mistake.
Flatlist has a prop called extraData.
This prop tells Flatlist whether to re-render or not.
If data in extraData changes then flatlist re-renders based on new data provided in data prop.
So whenever you need to re-render flatlist just change something in extraData.
Best way is to pass state toextraData which is passed to Data.
So, just pass extraData={this.state.obj}.
there also other way called forceUpdate.
you can call this.forceUpdate().
but this is not recommended because this will render not only flatlist but entire component in which you are calling this.
I created a custom List component from the react-native flatList component. Now I want to use the scrollToIndex method of the flatlist component using ref so that I can scroll to top of the list by pressing a custom button. But the scrollToIndex method seems to be not available when I create a custom component. How to make this work?
You can pass it down through props
Your custom component "list" file:
const List = (props) => {
return (
<Flatlist
ref={(ref) => { this.listRef = ref; }}
initialScrollIndex={this.props.initialScrollIndex}
/>
);
};
In use:
scrollToIndex = () => {
this.listRef.scrollToIndex({animated: true, index: whateverIndex});
}
<List
initialScrollIndex={whateverIndex}
/>