There are couple of approaches:
-
Make Collect the app users launch and launch your custom app from the form to retrieve values. See https://docs.opendatakit.org/launch-apps-from-collect/ and note that you can populate multiple fields at once.
-
Write an instance XML file directly to
/sdcard/odk/instances
. You can either launch the instance selection list screen which will show those new instances to the user or populate the database through theInstanceProvider
. You can read more at Adding Instance to database - #2 by Mitch_S.