On-device storage

On-device storage saves measurements in the app's private storage on the phone. It needs no server, no accounts and no network connection.

Data endpoint

Where data goes is set by a single setting in the study protocol, the data endpoint. On-device storage, CAWS and your own server differ only in this setting; the rest of the protocol (what to collect, and when) stays the same.

For on-device storage, use one of two endpoints:

Configure the protocol

Start from the quickstart app and change the imports at the top of lib/main.dart to:

import 'package:carp_core/carp_core.dart' hide Smartphone;
import 'package:carp_mobile_sensing/carp_mobile_sensing.dart';

Smartphone exists in both packages; hide makes Dart use the one from carp_mobile_sensing.

Then, in _startSensing(), replace the protocol with the following steps.

1. Create the protocol and choose the endpoint

   The dataEndPoint is the one setting that decides where data goes:

   DatabaseFiles

   final protocol = SmartphoneStudyProtocol(
     name: 'My first study',
     dataEndPoint: SQLiteDataEndPoint(),
   );

   final protocol = SmartphoneStudyProtocol(
     name: 'My first study',
     dataEndPoint: FileDataEndPoint(),
   );

2. Add the phone and the participant

   The phone is the primary device that collects the data. The participant role represents the person using it.

   final phone = Smartphone();
   protocol.addPrimaryDevice(phone);
   protocol.addParticipantRole(ParticipantRole('Participant'));

3. Define what to collect, and when

   ImmediateTrigger starts collecting right away. BackgroundTask keeps collecting in the background.

   protocol.addTaskControl(
     ImmediateTrigger(),
     BackgroundTask(measures: [
       Measure(type: SensorSamplingPackage.STEP_EVENT),
       Measure(type: DeviceSamplingPackage.BATTERY_STATE),
       Measure(type: DeviceSamplingPackage.APP_LIFECYCLE_EVENT),
     ]),
     phone,
   );

4. Start the client

   This part is unchanged from the quickstart:

   final client = SmartPhoneClientManager();
   await client.configure();
   
   final study = await client.addStudyFromProtocol(protocol);
   await client.tryDeployment(study.studyDeploymentId, study.deviceRoleName);
   client.resume();

Retrieve the data

The data is stored in the app's private folder:

To copy the data to your computer:

Moving to a server

On-device storage suits trying things out. For a study, you usually want data to arrive centrally without accessing each phone. For that, use CARP Web Services or your own server.

For more detail, see Data managers.