ActivityPauseNotifier.java

package com.progscrape.ui;

import android.app.Activity;
import android.app.Application;
import android.os.Bundle;

import java.util.ArrayList;
import java.util.List;

import javax.inject.Inject;

public class ActivityPauseNotifier {
    private List<ActivityPauseNotification> listeners = new ArrayList<>();

    @Inject
    public ActivityPauseNotifier(final Application theApp, final Activity theActivity) {
        theApp.registerActivityLifecycleCallbacks(new Application.ActivityLifecycleCallbacks() {
            @Override
            public void onActivityCreated(Activity activity, Bundle savedInstanceState) {

            }

            @Override
            public void onActivityStarted(Activity activity) {

            }

            @Override
            public void onActivityResumed(Activity activity) {
                if (activity == theActivity) {
                    List<ActivityPauseNotification> clone = new ArrayList<>(listeners);
                    for (ActivityPauseNotification notification : clone)
                        notification.onResume();
                }
            }

            @Override
            public void onActivityPaused(Activity activity) {
                if (activity == theActivity) {
                    List<ActivityPauseNotification> clone = new ArrayList<>(listeners);
                    for (ActivityPauseNotification notification : clone)
                        notification.onPause();
                }
            }

            @Override
            public void onActivityStopped(Activity activity) {

            }

            @Override
            public void onActivitySaveInstanceState(Activity activity, Bundle outState) {

            }

            @Override
            public void onActivityDestroyed(Activity activity) {

            }
        });
    }

    public void register(ActivityPauseNotification notifier) {
        listeners.add(notifier);
    }

    public void unregister(ActivityPauseNotification notifier) {
        listeners.remove(notifier);
    }

    public interface ActivityPauseNotification {
        void onPause();

        void onResume();
    }
}