Flutter

This is an optional library you can install if you're working with Flutter. It uses an internal queue to make calls fast and non-blocking. It also batches requests and flushes asynchronously, making it perfect to use in any part of your mobile app.

PostHog supports the iOS, macOS, Android and Web platforms.

Installation

PostHog is available for install via Pub.

Configuration

Set your PostHog API key and change the automatic event tracking on if you wish the library to take care of it for you.

Remember that the application lifecycle events won't have any special context set for you by the time it is initialized. If you are using a self-hosted instance of PostHog you will need to have the public hostname or IP for your instance as well.

To start, add posthog_flutter to your pubspec.yaml:

pubspec.yaml

# rest of your code

dependencies:
  flutter:
    sdk: flutter
  posthog_flutter: ^4.0.1

# rest of your code

Then complete the set up for each platform:

Android setup

For Android, add your PostHog configuration to your AndroidManifest.xml file located in the android/app/src/main:

android/app/src/main/AndroidManifest.xml

<manifest xmlns:android="http://schemas.android.com/apk/res/android" package="your.package.name">
    <application>
        <!-- ... other configuration ... -->
        <meta-data android:name="com.posthog.posthog.API_KEY" android:value="<ph_project_api_key>" />
        <meta-data android:name="com.posthog.posthog.POSTHOG_HOST" android:value="<ph_instance_address>" />  <!-- usually 'https://app.posthog.com' or 'https://eu.posthog.com' -->
        <meta-data android:name="com.posthog.posthog.TRACK_APPLICATION_LIFECYCLE_EVENTS" android:value="true" />
        <meta-data android:name="com.posthog.posthog.DEBUG" android:value="true" />
    </application>
</manifest>

You'll also need to update the minimum Android SDK version to 21 in android/app/build.gradle:

android/app/build.gradle

// rest of your config

    defaultConfig {
      minSdkVersion 21
      // rest of your config
    }

// rest of your config

You may also need to ensure you're running on the latest Kotlin version. To do this, go to the Kotlin website to find the latest version number. Then set this version number in the build.gradle in the root of your android directory (and not the build.gradle located in android/app):

android/build.gradle

buildscript {
    ext.kotlin_version = '1.9.22' // use the latest Kotlin version number here
    // rest of config

iOS setup

For iOS, you'll need to have Cocoapods installed. Then add your PostHog configuration to the Info.plist file located in the ios/Runner directory:

XML

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
<!-- rest of your configuration -->
  <key>com.posthog.posthog.API_KEY</key>
  <string><ph_project_api_key></string>
  <key>com.posthog.posthog.POSTHOG_HOST</key>
  <string><ph_instance_address></string>
  <key>com.posthog.posthog.CAPTURE_APPLICATION_LIFECYCLE_EVENTS</key>
  <true/>
  <key>com.posthog.posthog.DEBUG</key>
  <true/>
</dict>
</plist>

Then you need to set the minimum platform version to iOS 13.0 in your Podfile:

YAML

platform :ios, '13.0'

# rest of your config

Web setup

For Web, add your Web snippet (which you can find in your project settings) in the <header> of your web/index.html file:

web/index.html

<!DOCTYPE html>
<html>

<head>
  <!-- ... other head elements ... -->

  <script async>
    !function(t,e){var o,n,p,r;e.__SV||(window.posthog=e,e._i=[],e.init=function(i,s,a){function g(t,e){var o=e.split(".");2==o.length&&(t=t[o[0]],e=o[1]),t[e]=function(){t.push([e].concat(Array.prototype.slice.call(arguments,0)))}}(p=t.createElement("script")).type="text/javascript",p.async=!0,p.src=s.api_host+"/static/array.js",(r=t.getElementsByTagName("script")[0]).parentNode.insertBefore(p,r);var u=e;for(void 0!==a?u=e[a]=[]:a="posthog",u.people=u.people||[],u.toString=function(t){var e="posthog";return"posthog"!==a&&(e+="."+a),t||(e+=" (stub)"),e},u.people.toString=function(){return u.toString(1)+".people (stub)"},o="capture identify alias people.set people.set_once set_config register register_once unregister opt_out_capturing has_opted_out_capturing opt_in_capturing reset isFeatureEnabled onFeatureFlags getFeatureFlag getFeatureFlagPayload reloadFeatureFlags group updateEarlyAccessFeatureEnrollment getEarlyAccessFeatures getActiveMatchingSurveys getSurveys onSessionId".split(" "),n=0;n<o.length;n++)g(u,o[n]);e._i.push([i,s,a])},e.__SV=1)}(document,window.posthog||[]);
    posthog.init(
      '<ph_project_api_key>',
      {
        api_host:'<ph_instance_address>', // 'https://app.posthog.com' or 'https://eu.posthog.com'
      }
    )
  </script>
</head>

<!-- other elements -->

</html>

For more information please check: https://posthog.com/docs/libraries/js

Usage

To use this, add posthog_flutter as a dependency in your pubspec.yaml file.

Example

Dart

import 'package:flutter/material.dart';
import 'package:posthog_flutter/posthog_flutter.dart';

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      navigatorObservers: [
        // The PosthogObserver records screen views automatically
        PosthogObserver(),
      ],
      home: Scaffold(
        appBar: AppBar(
          title: Text('PostHog example app'),
        ),
        body: Center(
          child: FlatButton(
            child: Text('TRACK ACTION WITH PostHog'),
            onPressed: () async {
              await Posthog().capture(
                eventName: 'ButtonClicked',
                properties: {
                  'foo': 'bar',
                  'number': 1337,
                  'clicked': true,
                },
              );
            },
          ),
        ),
      )
    );
  }
}

Capturing events

You can send custom events using capture:

Dart

await Posthog().capture(
  eventName: 'user_signed_up',
);

Tip: We recommend using a '[object][verb]' format for your event names, where '[object]' is the entity that the behavior relates to, and '[verb]' is the behavior itself. For example, project created, user signed up, or invite sent.

Setting event properties

Optionally, you can also include additional information in the event by setting the properties value:

Dart

await Posthog().capture(
  eventName: 'user_signed_up',
  properties: {
    'login_type': 'email',
    'is_free_trial': true
  }
);

Autocapture

PostHog autocapture automatically tracks the following events for you:

Application Opened - when the app is opened from a closed state or when the app comes to the foreground (e.g. from the app switcher)
Application Backgrounded - when the app is sent to the background by the user
Application Installed - when the app is installed.
Application Updated - when the app is updated.
$screen - when the user navigates (if using navigatorObservers or go_router)

Identify

We highly recommend reading our section on Identifying users to better understand how to correctly use this method.

Using identify, you can associate events with specific users. This enables you to gain full insights as to how they're using your product across different sessions, devices, and platforms.

An identify call has the following arguments:

userId: Required. A unique identifier for your user. Typically either their email or database ID.
userProperties: Optional. A dictionary with key:value pairs to set the user properties
userPropertiesSetOnce: Optional. Similar to userProperties. See the difference between userProperties and userPropertiesSetOnce

Dart

await Posthog().identify(
  userId: emailController.text, 
  userProperties: {"name": "Peter Griffin", "email": "peter@familyguy.com"},
  userPropertiesSetOnce: {"date_of_first_log_in": "2024-03-01"}
);

You should call identify as soon as you're able to. Typically, this is every time your app loads for the first time as well as directly after your user logs in. This ensures that events sent during your user's sessions are correctly associated with them.

When you call identify, all previously tracked anonymous events will be linked to the user.

Group analytics

Group analytics allows you to associate the events for that person's session with a group (e.g. teams, organizations, etc.). Read the Group Analytics guide for more information.

Note: This is a paid feature and is not available on the open-source or free cloud plan. Learn more here.

Associate the events for this session with a group

Dart

await Posthog().group(groupType: "company", groupKey: "company_id_in_your_db");

Associate the events for this session with a group AND update the properties of that group

Swift

await Posthog().group(
  groupType: "company", 
  groupKey: "company_id_in_your_db", 
  groupProperties: {
    "name": "ACME Corp"
});

The name is a special property which is used in the PostHog UI for the name of the Group. If you don't specify a name property, the group ID will be used instead.

Feature Flags

PostHog's feature flags enable you to safely deploy and roll back new features.

Boolean feature flags

Dart

if (await Posthog().isFeatureEnabled('flag-key')) {
    // Do something differently for this user

    // Optional: fetch the payload
    final matchedFlagPayload = await Posthog().getFeatureFlagPayload('flag-key');
}

Multivariate feature flags

Dart

if (await Posthog().getFeatureFlag('flag-key') == 'variant-key') { // replace 'variant-key' with the key of your variant
    // Do something differently for this user

    // Optional: fetch the payload
    final matchedFlagPayload = await Posthog().getFeatureFlagPayload('flag-key');
}

Ensuring flags are loaded before usage

Every time a user loads a screen, we send a request in the background to fetch the feature flags that apply to that user. We store those flags in the storage.

This means that for most screens, the feature flags are available immediately – except for the first time a user visits.

Reloading feature flags

Feature flag values are cached. If something has changed with your user and you'd like to refetch their flag values, call:

Dart

await Posthog().reloadFeatureFlags();

Issues

Please file any issues, bugs, or feature requests in our GitHub repository.

Contributing

If you wish to contribute a change to this repo, please send a Pull Request.

Which features are available in this library?

Installation

Configuration

Android setup

iOS setup

Web setup

Usage

Example

Capturing events

Setting event properties

Autocapture

Identify

Group analytics

Feature Flags

Boolean feature flags

Multivariate feature flags

Ensuring flags are loaded before usage

Reloading feature flags

Issues

Contributing

Questions?

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