Quickstart

Build a Flutter app that collects the call log, text messages and calendar events with hashed identifiers.

The finished app reads calls, text messages and calendar events on a schedule and prints them with phone numbers and texts hashed.

Prerequisites

The setup in Installation, including the CARP Mobile Sensing (CAMS) setup it builds on.
A physical phone with some calls, text messages and calendar events. On iOS, only the calendar is collected.

Complete example

Replace the contents of lib/main.dart with:

lib/main.dart

import 'dart:convert';

import 'package:flutter/material.dart';
import 'package:carp_core/carp_core.dart' hide Smartphone;
import 'package:carp_mobile_sensing/carp_mobile_sensing.dart';
import 'package:carp_communication_package/communication.dart';

void main() async {
  WidgetsFlutterBinding.ensureInitialized();
  CarpMobileSensing.ensureInitialized();

  // 1. Register the sampling package
  SamplingPackageRegistry().register(CommunicationSamplingPackage());

  // 2. Create a protocol that hashes numbers, names and texts
  final protocol = SmartphoneStudyProtocol(
    ownerId: 'owner@example.com',
    name: 'Calls, messages and calendar',
    dataEndPoint: SQLiteDataEndPoint(),
    privacySchemaName: PrivacySchema.DEFAULT,
  );
  final phone = Smartphone();
  protocol.addPrimaryDevice(phone);

  // 3. Collect the call log and the calendar every 3 hours
  protocol.addTaskControl(
    PeriodicTrigger(period: const Duration(hours: 3)),
    BackgroundTask(
      measures: [
        Measure(type: CommunicationSamplingPackage.PHONE_LOG),
        Measure(type: CommunicationSamplingPackage.CALENDAR),
      ],
    ),
    phone,
  );

  // 4. Collect the text message log once a day
  protocol.addTaskControl(
    PeriodicTrigger(period: const Duration(days: 1)),
    BackgroundTask(
      measures: [Measure(type: CommunicationSamplingPackage.TEXT_MESSAGE_LOG)],
    ),
    phone,
  );

  // 5. Deploy the protocol on the first run and start sampling
  final client = SmartPhoneClientManager();
  await client.configure();
  if (client.studies.isEmpty) {
    final study = await client.addStudyFromProtocol(protocol);
    await client.tryDeployment(study.studyDeploymentId, study.deviceRoleName);
  }
  client.resume();

  // 6. Print each measurement as JSON
  client.measurements.listen((measurement) => print(jsonEncode(measurement)));

  runApp(
    const MaterialApp(
      home: Scaffold(body: Center(child: Text('Collecting data'))),
    ),
  );
}

How it works

Stage	What it does
1. Register	Makes the four measure types, the JSON types of their data and their privacy transformers known to CAMS. `CarpMobileSensing.ensureInitialized()` runs first, because registering needs an initialized CAMS.
2. Protocol	`privacySchemaName: PrivacySchema.DEFAULT` turns on the privacy transformers, which hash phone numbers, contact names, message texts and event titles. Without it, CAMS stores them in clear text.
3. Calls and calendar	`PeriodicTrigger` fires when sampling starts and then every 3 hours. Each run collects from the end of the previous run, and the first run goes back 1 day.
4. Text messages	The text message log returns every message in the inbox and the sent folder on each run, so a daily trigger keeps the duplicates down.
5. Deploy	CAMS asks for the permissions of all measures and then starts the triggers. The app adds the study only on the first run: on later runs, `configure()` restores the saved study.
6. Print	`client.measurements` delivers each measurement after the privacy transformers have run.

The phone log and the calendar keep their last collection time in memory. After an app restart, their first run goes back 1 day again. To keep the time across restarts, see Calls and text messages.

Run the app

Connect the phone and run:

flutter run

On Android, CAMS asks for access to phone calls, call logs, the calendar and SMS; on iOS, it asks for calendar access only. Allow them.

The first run starts right away, and the console prints a measurement for each measure that runs on the phone. CAMS also adds a dk.cachet.carp.triggeredtask measurement each time a trigger fires.

A calendar measurement looks like this, with the event titles and descriptions hashed and the JSON formatted for readability:

{
  "sensorStartTime": 1793019600512345,
  "sensorEndTime": 1793106000512345,
  "data": {
    "__type": "dk.cachet.carp.calendar",
    "calendarEvents": [
      {
        "eventId": "1187",
        "calendarId": "5",
        "title": "8a1e29b3dd009e1104338701230be5d7a38b1fed",
        "start": "2026-10-25T23:00:00.000Z",
        "end": "2026-10-26T23:00:00.000Z",
        "allDay": true,
        "status": "confirmed",
        "isRecurring": false
      },
      {
        "eventId": "1042",
        "calendarId": "3",
        "title": "9de5cdd1cef9a6467ce3e02cc92e0daeb6096368",
        "description": "938980c5b8c9f71c1637aa265cc3191ed40d4314",
        "start": "2026-10-27T08:00:00.000Z",
        "end": "2026-10-27T09:00:00.000Z",
        "allDay": false,
        "location": "Room 101",
        "status": "confirmed",
        "timeZone": "Europe/Copenhagen",
        "isRecurring": true
      }
    ],
    "start": "2026-10-26T14:00:00.512345",
    "end": "2026-10-27T14:00:00.512345"
  }
}

For the fields of each measure, see Calls and text messages and Calendar.

Check that the participant allowed every dialog, and that the permissions are in the merged manifest. An app that removes the restricted permissions for Google Play collects the calendar only. See Installation for the entries each measure needs.

Only calendar data on iOS

Use an Android phone to collect calls and text messages: iOS gives apps no access to them, so CAMS skips those measures on iOS.

Next steps

Calls and text messages

What the call and message measures collect, and their data.

Calendar

Which events the calendar measure collects, and their fields.

Privacy

Hash phone numbers, message texts and event titles before storage.