IsAndroidAppForeground.java

 static boolean isApplicationForeground(Context context) {
    KeyguardManager keyguardManager =
        (KeyguardManager) context.getSystemService(Context.KEYGUARD_SERVICE);

    if (keyguardManager != null && keyguardManager.isKeyguardLocked()) {
      return false;
    }

    ActivityManager activityManager =
        (ActivityManager) context.getSystemService(Context.ACTIVITY_SERVICE);
    if (activityManager == null) return false;

    List<ActivityManager.RunningAppProcessInfo> appProcesses =
        activityManager.getRunningAppProcesses();
    if (appProcesses == null) return false;

    final String packageName = context.getPackageName();
    for (ActivityManager.RunningAppProcessInfo appProcess : appProcesses) {
      if (appProcess.importance == ActivityManager.RunningAppProcessInfo.IMPORTANCE_FOREGROUND
          && appProcess.processName.equals(packageName)) {
        return true;
      }
    }

    return false;
  }