Yes, it is possible for an Android app to detect when Fennec (a Firefox-based browser for Android) starts playing media, but the approach depends on the type of detection you want to implement and the permissions available to your app. Here are the most common methods:

1. Accessibility Service

If your app has Accessibility Service permissions, it can monitor the device for media playback events, including those from Fennec.

How it works:

• The Accessibility Service can detect media session events (e.g., play, pause, stop) from apps like Fennec.
• You can listen for AccessibilityEvent.TYPE_WINDOW_STATE_CHANGED or AccessibilityEvent.TYPE_WINDOW_CONTENT_CHANGED and check if the active window belongs to Fennec.
• You can also use the MediaSessionManager API to detect active media sessions.

Limitations:

• Requires the user to explicitly enable the Accessibility Service for your app.
• May not work reliably for all media playback scenarios, especially if Fennec does not expose its media session publicly.

2. MediaSession API (Android 5.0+)

If Fennec exposes its media playback via the MediaSession API, your app can detect when media starts playing.

How it works:

• Use MediaSessionManager to get a list of active MediaController instances.
• Check if any of the active sessions belong to Fennec (e.g., by checking the package name or session ID).
• Listen for playback state changes (e.g., PlaybackState.STATE_PLAYING).

Example Code:

MediaSessionManager mediaSessionManager =
    (MediaSessionManager) getSystemService(Context.MEDIA_SESSION_SERVICE);
List<MediaController> controllers = mediaSessionManager.getActiveSessions(null);

for (MediaController controller : controllers) {
    if (controller.getPackageName().equals("org.mozilla.fenix")) {
        // Fennec is playing media
        PlaybackState state = controller.getPlaybackState();
        if (state != null && state.getState() == PlaybackState.STATE_PLAYING) {
            // Media is playing
        }
    }
}

Limitations:

• Requires Fennec to expose its media session publicly.
• May not work if Fennec does not use the MediaSession API.

3. Notification Listener Service

If Fennec displays a media notification (e.g., a notification with play/pause buttons), your app can use the Notification Listener Service to detect when such a notification appears.

How it works:

• Implement a NotificationListenerService to monitor notifications.
• Check for notifications posted by Fennec (package name: org.mozilla.fenix).
• Look for notifications with media controls (e.g., Notification.MediaStyle).

Limitations:

• Requires the user to grant notification access to your app.
• Only works if Fennec displays a notification for media playback.

4. Usage Stats API (Android 5.0+)

If your app has the android.permission.PACKAGE_USAGE_STATS permission, it can check when Fennec is in the foreground and infer media playback.

How it works:

• Use UsageStatsManager to query the usage stats of Fennec.
• Check if Fennec is in the foreground and if its usage time increases, which may indicate media playback.

Limitations:

• Requires the user to explicitly grant the PACKAGE_USAGE_STATS permission.
• Does not directly detect media playback; it only infers it based on app usage.

5. Audio Focus Detection

If your app is already playing audio, it can detect when another app (like Fennec) takes audio focus.

How it works:

• Implement an OnAudioFocusChangeListener to monitor audio focus changes.
• When Fennec starts playing media, it may request audio focus, triggering your listener.

Limitations:

• Only works if your app is already using audio focus.
• Does not directly detect Fennec; it only detects when audio focus is lost.

6. Custom Fennec Integration

If you have control over the Fennec app (e.g., it is a custom build), you could:

• Add a broadcast or content provider to notify your app when media starts playing.
• Use Inter-Process Communication (IPC) to communicate between Fennec and your app.

Limitations:

• Requires modifications to Fennec, which is not feasible for the standard version.

Which Method Should You Use?

Recommendation

• If you need reliable detection, use the Accessibility Service or Notification Listener Service.
• If you want a lightweight solution, try the MediaSession API (if Fennec supports it).
• If you only need inferences, use the Usage Stats API.

Would you like help implementing any of these methods in your app?