public class Helper {

        public static boolean isAppRunning(final Context context, final String packageName) {
            final ActivityManager activityManager = (ActivityManager) context.getSystemService(Context.ACTIVITY_SERVICE);
            final List<ActivityManager.RunningAppProcessInfo> procInfos = activityManager.getRunningAppProcesses();
            if (procInfos != null)
            {
                for (final ActivityManager.RunningAppProcessInfo processInfo : procInfos) {
                    if (processInfo.processName.equals(packageName)) {
                        return true;
                    }
                }
            }
            return false;
        }
    }

if (Helper.isAppRunning(YourActivity.this, "com.your.desired.app")) {
    // App is running
} else {
    // App is not running
}