IOS Geofence Tracking Issue After Schedule End

Dec 5, 2025 by Alex Johnson 47 views

iOS Geofence-Only Tracking Continues After Schedule End Bug

Understanding the iOS Geofence Bug

Flutter Background Geolocation is a powerful tool for location tracking in mobile applications. However, a specific bug has been identified in the iOS implementation of the flutter_background_geolocation plugin, specifically concerning geofence-only tracking with scheduled periods. This issue causes geofence events to persist beyond the defined schedule, leading to unexpected behavior. Geofence technology allows applications to trigger actions based on a user's proximity to a defined geographic area. This is extremely useful for location-aware features, such as automatic check-ins, location-based notifications, and more. In this context, a user sets up a geofence and wants the application to behave in a certain way only when the user is within that geofence, or during a specific scheduled period. The core issue lies in how the plugin handles the end of a scheduled geofence-only tracking session on iOS compared to its Android counterpart. The expected behavior is that after the scheduled time expires, the geofence tracking should cease, and the application should no longer receive geofence events unless the user re-enters the geofence. However, on iOS, the geofence events continue to fire even after the schedule has ended, potentially for extended periods, and even the next day if the user returns to the geofence.

The Problem in Detail

The bug manifests when using geofence-only mode combined with a short schedule. The developer sets up a schedule (e.g., 2 minutes) for geofence tracking after an EXIT event. In Android, the tracking stops correctly after the 2-minute window. Returning to the geofence after this period does not trigger an ENTER event, as expected. But on iOS, ENTER events continue to be triggered well after the scheduled 2-minute window has passed. This can lead to significant issues. For example, in an application designed for time tracking, this bug can cause incorrect reporting of work hours or inaccurate location-based triggers. The logs confirm that the tracking was initiated with the proper schedule times, further indicating that the issue lies in the plugin's handling of the schedule termination on iOS, not in the initial setup. This discrepancy between iOS and Android is a critical concern, as it undermines the reliability of location-based services built using this plugin on iOS devices.

Reproducing the Bug

The steps to reproduce this bug are straightforward:

Initialize the Plugin: Set up the flutter_background_geolocation plugin and register a listener for onGeofence events.
Trigger on EXIT: When an EXIT event occurs (user leaves the geofence), start geofence-only tracking with a schedule that ends in a short time (e.g., 2 minutes).
Simulate Re-entry: Wait for longer than the specified 2 minutes and then re-enter the same geofence.
Observe the Difference: On iOS, an ENTER event will be fired again, even though the schedule should have ended. On Android, the ENTER event will not be triggered.

This reproducible scenario highlights the core issue and offers a clear path for developers to test and verify the presence of the bug in their applications. Understanding these steps is crucial for developers relying on the plugin, as it allows them to recognize the issue and implement workarounds if necessary. In essence, the bug affects the accuracy and reliability of location-based features within an application.

Code and Configuration Analysis

Plugin Initialization and Configuration

The provided code snippet details how the flutter_background_geolocation plugin is initialized and configured. It sets up an onGeofence listener, which is crucial for reacting to geofence events. This listener is the core of the location monitoring system. Inside the onGeofence event handler, a check is made to see if the user has left a geofence (event.action == GeofenceEventAction.exit.value). If so, a function _startCheckedOutTracking() is called to initiate the scheduled tracking.

The _getDefaultConfig() function sets various configuration options such as desired accuracy, distance filter, and notification settings. The geofenceModeHighAccuracy option suggests the plugin is configured to use the highest accuracy for geofence monitoring. The debug flag enables verbose logging for easier troubleshooting. The notification settings configure the appearance of location tracking notifications, which can be useful for informing the user that location services are active. This is an important consideration for respecting user privacy and ensuring transparency about data collection.

Scheduled Tracking Implementation

The _startCheckedOutTracking() function calls _trackForMinutes() to set up the scheduled tracking. This function calculates the end time for the tracking schedule and constructs a schedule string. It then uses bg.BackgroundGeolocation.stopSchedule() and bg.BackgroundGeolocation.setConfig() to update the plugin’s configuration with the new schedule, and calls bg.BackgroundGeolocation.startGeofences() and bg.BackgroundGeolocation.startSchedule() to activate the geofence tracking with the defined schedule. This approach aims to provide a short, time-limited tracking window. The core issue arises when this scheduled window is not respected on iOS. The scheduleStr variable is formatted to specify the start and end times for tracking. The code then uses this formatted string to configure the plugin's schedule. This schedule should ideally limit the tracking duration; however, on iOS, the schedule's end time seems to be ignored, resulting in the extended tracking behavior.

The use of startGeofences() and startSchedule() suggests that the plugin is correctly set up to monitor geofences and adhere to the specified schedules. This emphasizes that the bug is likely in the plugin's implementation of these functions on iOS.

Log Analysis and Expected Behavior

Examining the Logs

The provided logs offer crucial insights into the plugin's behavior. The logs show that at 22:32:48, the tracking was started inside the geofence using the schedule. At 22:35:04, the EXIT event occurred, triggering a new tracking schedule ending in 2 minutes (at 22:37). However, the logs show an ENTER geofence event occurring at 22:06, long after the tracking should have stopped. This clearly demonstrates the issue: the scheduled tracking, designed to last only a few minutes, is not terminating correctly on iOS.

The logs are detailed and provide timestamps that allow for precise analysis of the events. Analyzing the logs helps confirm the timing and the unexpected continued firing of events. The TSScheduler logs are particularly important, as they show the schedule being parsed and triggered. The logs indicate that the plugin correctly sets up the schedule. The TSGeofenceManager logs help trace the geofence events and verify the ENTER and EXIT events are correctly identified. These logs should show when the geofence events are fired, revealing the discrepancy between expected and actual behavior. The logs also reveal various plugin states, such as when the location services are enabled or disabled, helping pinpoint where the issue arises.

Expected vs. Actual Behavior

The expected behavior is that geofence events should cease to be triggered after the scheduled 2-minute window, and an ENTER event should not fire until the user re-enters the geofence after this period. The actual behavior, as demonstrated by the logs, shows that ENTER events continue to be fired even after the schedule expires. The expected behavior ensures that the application respects the scheduled tracking period. This is critical for managing battery life and user privacy. Unexpected behavior, on the other hand, means that the application might be tracking location data longer than intended, potentially draining battery and violating the user's expectations about when their location is being tracked.

Conclusion and Potential Solutions

Identifying the Root Cause

The core of the problem appears to be in the iOS-specific implementation of the flutter_background_geolocation plugin. While the configuration and setup seem to be correct, the plugin's ability to accurately manage the end of the scheduled geofence tracking is failing. This suggests that the issue might be in how the plugin interacts with the iOS location services or how it handles the schedule termination.

Potential Workarounds

1. Manual Geofence Management: Implement a custom timer or a more elaborate logic within the onGeofence listener. When an EXIT event occurs, start a timer that will stop the geofence tracking after the specified duration. This approach would bypass the plugin's scheduling mechanism. 2. Background Task Termination: If possible, attempt to manually stop the location updates or the background service after the schedule time. This could involve using the BackgroundGeolocation.stop() function after the schedule's end time. This strategy relies on direct control over the plugin's operation. 3. Conditional Event Handling: Add conditional checks within the onGeofence listener. Check the current time against the scheduled end time and ignore any ENTER events that occur outside the schedule. This approach could be used in conjunction with a timer to prevent any further processing of location events.

Long-Term Solutions

1. Plugin Update: The most effective long-term solution is to wait for a bug fix from the plugin developers. This would involve them identifying and resolving the issue within the plugin's iOS implementation. The developers need to address the scheduling logic for geofence tracking on iOS. 2. Community Collaboration: Engage with the flutter_background_geolocation plugin community by reporting the issue and providing detailed information about the bug, including the code, logs, and steps to reproduce. This could speed up the resolution of the bug. 3. Testing and Validation: Regularly test the application's location services on both iOS and Android to ensure that the bug is resolved in future plugin versions or to verify the efficacy of the applied workaround.

This analysis clarifies the bug's nature, its impact, and its relation to the application's functionality. By understanding this, developers can create more reliable location-based features, and the plugin developers will be able to resolve the issue more effectively.

For more information on geofencing, please visit Transistor Software's Documentation.