Customize ChannelList
Let's look at how to make some customizations to ChannelList
.
Customizing Event Handlers
ChannelList
uses Event Listeners to dynamically update when changes occur.
If a new message is received, a user is added to a channel, or other events take place, the ChannelList
will update its UI accordingly.
It's important to note that filters
don't apply to updates to the list from events.
The event type the ChannelList
reacts to and its corresponding behavior can be overridden using the appropriate prop.
Event Type | Default Behavior | Prop to override |
---|---|---|
channel.deleted | Remove channel from the list | onChannelDeleted |
channel.hidden | Remove channel from the list | onChannelHidden |
channel.truncated | Updates the channel | onChannelTruncated |
channel.updated | Updates the channel | onChannelUpdated |
channel.visible | Adds the channel to the list | onChannelVisible |
message.new | Moves the channel to top of the list | lockChannelOrder |
notification.added_to_channel | Adds the new channel to the top of the list and starts watching it | onAddedToChannel |
notification.message_new | Adds the new channel to the top of the list and starts watching it | onMessageNew |
notification.removed_from_channel | Removes the channel from the list | onRemovedFromChannel |
Let's take an example of ChannelList component for frozen channels.
const filters = {
members: { $in: ['vishal'] },
frozen: true
}
<ChannelList filters={filters} />
The notification.message_new
event occurs when a message is received on a channel that is not loaded but the current user is a member of.
The default behavior when this event occurs is to query the channel the message is received on, then add the channel to the top of the list, irrespective of filters
.
Thus, if new message appears in some unfrozen channel which current user is member of, it will be added to the list.
This may not be a desired behavior since the list is only supposed to show frozen channels.
In this case you can replace the default functionality by providing a custom onMessageNew
function as prop to ChannelList
component.
onMessageNew
receives two parameters when called, setChannels
, a setter function for the internal channels
state, and event
, the Event
object received for the notification.message_new
event.
These parameters can be used to create a function that achieves the desired custom behavior.
const filters = {
members: { $in: ['vishal'] },
frozen: true,
};
const customOnMessageNew = async (setChannels, event) => {
const eventChannel = event.channel;
// If the channel is frozen, then don't add it to the list.
if (!eventChannel?.id || !eventChannel.frozen) return;
try {
const newChannel = client.channel(eventChannel.type, eventChannel.id);
await newChannel.watch();
setChannels(channels => [newChannel, ...channels]);
} catch (error) {
console.log(error);
}
};
<ChannelList filters={filters} onMessageNew={customOnMessageNew} />;
Similarly, events other than notification.message_new can be handled as per application requirement.
Replacing infinite scroll pagination with "Load More" button
ChannelList
component accepts the List
prop, which is a component to render the list of channels.
Default value for this prop is ChannelListMessenger
and it consumes ChannelsContext
, which provides all the necessary values to implement infinite scroll pagination.
This component internally uses FlatList from react-native. And loadNextPage
function
from ChannelsContext
is attached to onEndReached prop of underlying FlatList to allow infinite scroll pagination.
Its possible to override the props on underlying FlatList by providing additionalFlatListProps
prop to ChannelList
or ChannelListMessenger
.
Thus "Load More" button can be added as ListFooterComponent for underlying FlatList and infinite scroll pagination can be disabled by overriding
the onEndReached prop for FlatList.
"Load More" button should invoke loadNextPage
function, when pressed.
Additionally, you can use pagination related flags such as loadNextPage
, hasNextPage
, loadingChannels
to handle the visibility of this button.
import { Button } from 'react-native';
import { useChannelsContext } from 'stream-chat-react-native';
const FooterLoadMoreButton = () => {
const { loadingChannels, loadNextPage, hasNextPage } = useChannelsContext();
if (loadingChannels || !hasNextPage) return null;
return <Button title={'Load More'} onPress={loadNextPage} />;
};
<ChannelList
additionalFlatListProps={{
ListFooterComponent: FooterLoadMoreButton,
onEndReached: () => null,
}}
/>;