How to Create a Custom Plugin in Mobile SDKs

import androidx.annotation.NonNull;
import androidx.annotation.Nullable;

import com.rudderstack.sdk.kotlin.core.Analytics;
import com.rudderstack.sdk.kotlin.core.internals.logger.LoggerAnalytics;
import com.rudderstack.sdk.kotlin.core.internals.models.Event;
import com.rudderstack.sdk.kotlin.core.internals.models.TrackEvent;
import com.rudderstack.sdk.kotlin.core.internals.plugins.Plugin;

import java.util.List;

import kotlin.coroutines.Continuation;

/**
 * A custom Java Plugin demonstrating how to perform event filtering in Java.
 */
public class JavaEventFilteringPlugin implements Plugin {
    private Analytics analytics;
    private static final Plugin.PluginType pluginType = Plugin.PluginType.OnProcess;

    List<String> listOfEventsToBeFiltered;

    @Override
    public void setAnalytics(@NonNull Analytics analytics) {
        this.analytics = analytics;
    }

    @Override
    public void setup(@NonNull Analytics analytics) {
        this.analytics = analytics;
        listOfEventsToBeFiltered = List.of("Application Opened", "Application Backgrounded");
    }

    @Nullable
    @Override
    public Object intercept(@NonNull Event event, @NonNull Continuation<? super Event> $completion) {
        if (event instanceof TrackEvent && listOfEventsToBeFiltered.contains(((TrackEvent) event).getEvent())) {
            LoggerAnalytics.INSTANCE.verbose("EventFilteringPlugin: Event " + ((TrackEvent) event).getEvent() + " is filtered out");
            return null;
        }

        return event;
    }

    @NonNull
    @Override
    public Analytics getAnalytics() {
        return this.analytics;
    }

    @NonNull
    @Override
    public Plugin.PluginType getPluginType() {
        return pluginType;
    }

    @Override
    public void teardown() {
        listOfEventsToBeFiltered = null;
    }
}

JavaEventFilteringPlugin eventFilteringPlugin = new JavaEventFilteringPlugin();

analytics.add(eventFilteringPlugin);

analytics.remove(eventFilteringPlugin);

@interface EventFilteringPlugin()

@property(nonatomic, retain) RSSAnalytics *client;
@property(nonatomic, retain) NSMutableArray *eventsToFilter;

@end

@implementation EventFilteringPlugin
@synthesize pluginType;

- (instancetype)init {
    self = [super init];
    if (self) {
    }
    return self;
}

- (RSSPluginType)pluginType {
    return RSSPluginTypeOnProcess;
}

- (void)setup:(RSSAnalytics * _Nonnull)analytics {
    self.client = analytics;
    self.eventsToFilter = [NSMutableArray arrayWithArray: @[@"Application Opened", @"Application Backgrounded"]];
}

- (RSSEvent * _Nullable)intercept:(RSSEvent * _Nonnull)event {
    if ([event isKindOfClass:[RSSTrackEvent class]]) {
        RSSTrackEvent *trackEvent = (RSSTrackEvent *)event;
        if ([self shouldFilterEvent:trackEvent]) {
            [RSSLoggerAnalytics verbose:[NSString stringWithFormat:@"EventFilteringPlugin: Event \"%@\" is filtered out.", trackEvent.eventName]];
            return nil; // Filter out this event
        }
    }
    return event; // Allow event to pass through
}

- (BOOL)shouldFilterEvent:(RSSTrackEvent *)trackEvent {
    return [self.eventsToFilter containsObject:trackEvent.eventName];
}

- (void)teardown {
    [self.eventsToFilter removeAllObjects];
    self.eventsToFilter = nil;
    self.client = nil;
}

EventFilteringPlugin *eventFilteringPlugin = [[EventFilteringPlugin alloc] init];

[self.analytics addPlugin: eventFilteringPlugin];

[self.analytics removePlugin:eventFilteringPlugin];