code: public static void startGalleryApp(@NonNull final Activity activity, final int requestCode) {
          Condition.INSTANCE.ensureNotNull(activity, "The activity may not be null");
          Intent intent =
                  new Intent(Intent.ACTION_PICK, MediaStore.Images.Media.EXTERNAL_CONTENT_URI);
  
          if (intent.resolveActivity(activity.getPackageManager()) == null) {
              throw new ActivityNotFoundException("Gallery app not available");
          }
  
          activity.startActivityForResult(intent, requestCode);
      }
docs: Starts the gallery app in order to choose a picture. In an error occurs while starting the
  gallery app, an {@link ActivityNotFoundException} will be thrown.
  
  @param activity
  The activity, the chosen image should be passed to by calling its
  <code>onActivityResult</code> method, as an instance of the class {@link Activity}.
  The activity may not be null
  @param requestCode
  The request code, which should be used to pass the captured picture to the given
  activity, as an {@link Integer} value