The EXTRA_ALLOW_MULTIPLE parameter is set in the intent using the Intent.putExtra () method to select multiple images
API 18
intent.putExtra(Intent.EXTRA_ALLOW_MULTIPLE, true);
:
Intent intent = new Intent(); intent.setType("image/*");
intent.putExtra(Intent.EXTRA_ALLOW_MULTIPLE, true);
intent.setAction(Intent.ACTION_GET_CONTENT);
startActivityForResult(Intent.createChooser(intent,"Select Picture"),1);