루팅 안해도 됩니다.
public String getCurrentInputMethodPackageName(Context context, ContentResolver resolver,
                                    InputMethodManager imm, List<InputMethodInfo> imis, PackageManager pm) {
   if (resolver == null || imis == null) return null;
   final String currentInputMethodId = Settings.Secure.getString(resolver,
         Settings.Secure.DEFAULT_INPUT_METHOD);
   if (TextUtils.isEmpty(currentInputMethodId)) return null;
   for (InputMethodInfo imi : imis) {
      if (currentInputMethodId.equals(imi.getId())) {
         return imi.getPackageName();
      }
   }
   return null;
}