I'm working on a React Native project and using the FlatList
component to render a list of items. Each item has an Updated
function that should update and display the elapsed time every 3 seconds.
React-Native
// Function to calculate and continuously update the elapsed time
const Updated = (item) => {
setInterval(() => {
// Extract the server timestamp from the item
const ServerStamp = item.time;
// Convert server timestamp to milliseconds
const serverTimeInMilliseconds = ServerStamp.seconds * 1000 + ServerStamp.nanoseconds / 1e6;
// Get the current time
const currentTime = new Date();
// Calculate the time passed since the server timestamp
const timePassedInMilliseconds = currentTime.getTime() - serverTimeInMilliseconds;
// Calculate hours
const hours = Math.floor(timePassedInMilliseconds / (60 * 60 * 1000));
// Calculate remaining milliseconds after hours
const remainingMilliseconds = timePassedInMilliseconds % (60 * 60 * 1000);
// Calculate minutes from remaining milliseconds
const minutes = Math.floor(remainingMilliseconds / (60 * 1000));
// Format the elapsed time as hours:minutes
const msgTime = hours + ':' + minutes;
// Log the formatted time to the console
console.log(msgTime);
// Return the formatted time (Note: this return statement is not used in your current code)
return msgTime;
}, 3000); // Update the elapsed time every 3 seconds
}
// renderItem method used in FlatList
const renderItem = ({ item }) => {
// Find the corresponding surname for the item
const surname = named.find((dataID) => dataID.id === item.id);
// Check if surname is found
if (surname) {
return (
<View style={{ padding: 16, borderBottomWidth: 1, borderBottomColor: '#ccc' }}>
{/* Display the name */}
<Text>Name: {surname.name}</Text>
{/* Call Updated function to display and continuously update the elapsed time */}
<Text>Minutes: {Updated(item)}</Text>
{/* Placeholder for Location */}
<Text>Location: ?</Text>
{/* Display the status */}
<Text>Status: {item.status}</Text>
{/* SelectList component for changing status */}
<SelectList
placeholderTextColor="#ccc"
search={true}
setSelected={(val) => handleStatusChange(val, item.id)}
data={statusOptions}
save="value"
color="white"
placeholder={item.status}
/>
</View>
);
}
};
// Main component JSX
return (
<View>
{/* FlatList component to render the list of items */}
<FlatList
data={person}
renderItem={renderItem}
keyExtractor={(item) => item.id}
/>
{/* Button for logging the timestamp of the first item in the console */}
<Button title='click' onPress={() => console.log(person[0].time)} />
</View>
);
`
i want to update the
<Text>Minutes: {Updated(item)}</Text> every 1min
You need to use React.useState in order to change React-Native props and values.
You can:
A- Have an ItemComponent outside main function with useState and useEffect. The Updated wont need setIntervals.
const Updated = () => {
// do something with time and return custom time
return Date.now();
};
const ItemComponent = ({ item }) => {
const [itemTime, setItemTime] = React.useState(() => Updated(item));
React.useEffect(() => {
const interval = setInterval(() => {
setItemTime(Updated(item));
}, 3000);
return () => clearInterval(interval);
}, []);
return (
<View>
<Text>{itemTime}</Text>
{/* otherComponents */}
</View>
);
};
function App() {
return (
<View>
<FlatList
data={person}
renderItem={({ item }) => <ItemComponent item={item} />}
keyExtractor={(item) => item.id}
/>
</View>
);
}
B- Convert update function into a hook
const useUpdateTime = (item) => {
const Updated = () => {
// do something with time and return custom time
return Date.now();
};
const [itemTime, setItemTime] = React.useState(() => Updated(item));
React.useEffect(() => {
const interval = setInterval(() => {
setItemTime(Updated(item));
}, 3000);
return () => clearInterval(interval);
}, []);
return itemTime;
};
const ItemComponent = ({ item }) => {
const itemTime = useUpdateTime(item);
return (
<View>
<Text>{itemTime}</Text>
{/* otherComponents */}
</View>
);
};
function App() {
return (
<View>
<FlatList
data={person}
renderItem={({ item }) => <ItemComponent item={item} />}
keyExtractor={(item) => item.id}
/>
</View>
);
}
There are other options like having useState and useEffect in main function and changing all items together.