Android: How can I get the current foreground activity (from a service)?

Question

Is there a native android way to get a reference to the currently running Activity from a service?

I have a service running on the background, and I would like to up

Answer 1

I could not find a solution that our team would be happy with so we rolled our own. We use ActivityLifecycleCallbacks to keep track of current activity and then expose it through a service:

public interface ContextProvider {
    Context getActivityContext();
}

public class MyApplication extends Application implements ContextProvider {
    private Activity currentActivity;

    @Override
    public Context getActivityContext() {
         return currentActivity;
    }

    @Override
    public void onCreate() {
        super.onCreate();

        registerActivityLifecycleCallbacks(new ActivityLifecycleCallbacks() {
            @Override
            public void onActivityCreated(Activity activity, Bundle savedInstanceState) {
                MyApplication.this.currentActivity = activity;
            }

            @Override
            public void onActivityStarted(Activity activity) {
                MyApplication.this.currentActivity = activity;
            }

            @Override
            public void onActivityResumed(Activity activity) {
                MyApplication.this.currentActivity = activity;
            }

            @Override
            public void onActivityPaused(Activity activity) {
                MyApplication.this.currentActivity = null;
            }

            @Override
            public void onActivityStopped(Activity activity) {
                // don't clear current activity because activity may get stopped after
                // the new activity is resumed
            }

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

            }

            @Override
            public void onActivityDestroyed(Activity activity) {
                // don't clear current activity because activity may get destroyed after
                // the new activity is resumed
            }
        });
    }
}

Then configure your DI container to return instance of MyApplication for ContextProvider, e.g.

public class ApplicationModule extends AbstractModule {    
    @Provides
    ContextProvider provideMainActivity() {
        return MyApplication.getCurrent();
    }
}

(Note that implementation of getCurrent() is omitted from the code above. It's just a static variable that's set from the application constructor)