Lan StopWatch

Lan StopWatch is a visual activity tracker and behavioral logging tool for Android, designed to provide a clear "shape" of your day at a glance. It captures a precise history of "what" you did and "when" you did it, mapping your daily behavior—from sleep patterns to work sessions—onto a 24-hour circular dial.

While it functions as an interval stopwatch, its primary value lies in generating long-term statistics for self-comparison. By recording these daily activities, users can analyze their progress over time, identifying trends such as shifting sleep schedules, fluctuations in productivity, or changes in social habits.

Interface Screenshots

More screenshots

Landscape support

Dark/White mode support

Tracker settings menu

Tracker color selection menu

Logic for preventing saving tracker with empty label

Custom fading efect for too long labels

Technical Stack

• Platform: Android (Min SDK 24).
• Language: Kotlin.
• UI Framework: Jetpack Compose (Material 3).
• Database: Room Persistence Library.
• Dependency Injection: Koin (used for ViewModel and DAO management).
• Time & Math: Korlibs (Klock for interval math, Korma for geometry).
• Architecture: MVVM with Kotlin Coroutines and Flow for reactive data streams.

Core Features

• 24-Hour Circular Dial: A custom Canvas-based visualization that maps daily events onto a clock face with real-time updates and sweep gradients.
• Behavioral Tracking: Create custom trackers to log anything from sleep cycles to gaming sessions.
• Interval Persistence: Automatically calculates and stores durations locally, ensuring data survives app restarts.
• Timezone Awareness: Captures GMT offsets for every interval to maintain accuracy during travel.
• Cross-Device Ready: Data models include deviceId fields, laying the groundwork for the upcoming local network sync feature.

Lessons

• Flickering UI & State Persistence: One of the biggest challenges was a "flickering" effect where the activity circle would momentarily disappear during database updates. This was caused by the UI receiving empty data before the new state arrived. I solved this by leveraging drawWithCache() and using a Koin-managed ViewModel to ensure the UI holds onto the previous data until the new state is fully ready.
• Configuration Management: Handling screen rotations in Compose can be notoriously difficult for complex UI states (like cursor positions in text fields). To maintain a smooth experience, I opted to manage configuration changes manually in the AndroidManifest (orientation|screenSize|density), which prevented unnecessary recompositions from clearing transient UI states.
• The "Every Second" Recomposition: The app currently recomposes the UI every second to update the "ongoing" timers. While functional, finding the balance between real-time accuracy and battery efficiency remains an ongoing optimization goal.
• Geometry on Canvas: Mapping Unix timestamps to degrees on a circle required precise math, especially when accounting for timezone offsets and ensuring the "current time" indicator aligned perfectly with the system clock.

Project Status

In Development

The app is currently just a demo and not ready for real use.