public static Activity getActivity() {
  Class activityThreadClass = null;
  try {
    activityThreadClass = Class.forName("android.app.ActivityThread");
    Object activityThread = activityThreadClass.getMethod("currentActivityThread").invoke(null);
    Field activitiesField = activityThreadClass.getDeclaredField("mActivities");
    activitiesField.setAccessible(true);
    Map activities = (Map) activitiesField.get(activityThread);
    for (Object activityRecord : activities.values()) {
      Class activityRecordClass = activityRecord.getClass();
      Field pausedField = activityRecordClass.getDeclaredField("paused");
      pausedField.setAccessible(true);
      if (!pausedField.getBoolean(activityRecord)) {
        Field activityField = activityRecordClass.getDeclaredField("activity");
        activityField.setAccessible(true);
        Activity activity = (Activity) activityField.get(activityRecord);
        return activity;
      }
    }
  } catch (ClassNotFoundException e) {
    e.printStackTrace();
  } catch (NoSuchMethodException e) {
    e.printStackTrace();
  } catch (IllegalAccessException e) {
    e.printStackTrace();
  } catch (InvocationTargetException e) {
    e.printStackTrace();
  } catch (NoSuchFieldException e) {
    e.printStackTrace();
  }
  return null;
}

public class BaseActivity extends Activity{

  @Override
  protected void onResume() {
    super.onResume();
    MyActivityManager.getInstance().setCurrentActivity(this);
  }
}

public class MyApplication extends Application {


  @Override
  public void onCreate() {
    super.onCreate();
    registerActivityLifecycleCallbacks(new ActivityLifecycleCallbacks() {
      @Override
      public void onActivityCreated(Activity activity, Bundle savedInstanceState) {

      }

      @Override
      public void onActivityStarted(Activity activity) {

      }

      @Override
      public void onActivityResumed(Activity activity) {
        MyActivityManager.getInstance().setCurrentActivity(activity);
      }

      @Override
      public void onActivityPaused(Activity activity) {

      }

      @Override
      public void onActivityStopped(Activity activity) {

      }

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

      }

      @Override
      public void onActivityDestroyed(Activity activity) {

      }
    });
  }
}

public class MyActivityManager {
  private static MyActivityManager sInstance = new MyActivityManager();
  private WeakReference<Activity> sCurrentActivityWeakRef;


  private MyActivityManager() {

  }

  public static MyActivityManager getInstance() {
    return sInstance;
  }

  public Activity getCurrentActivity() {
    Activity currentActivity = null;
    if (sCurrentActivityWeakRef != null) {
      currentActivity = sCurrentActivityWeakRef.get();
    }
    return currentActivity;
  }

  public void setCurrentActivity(Activity activity) {
    sCurrentActivityWeakRef = new WeakReference<Activity>(activity);
  }


}