Build a Pomodoro Focus Timer in Flutter

I constructed a Pomodoro Focus Timer in Flutter called ZenPeace. It offers customizable focus intervals, including the standard 25/5 presets, as well as options for work and break lengths. A daily task planner allows users to assign urgency levels and pomodoro intervals to tasks. The app provides deep-work analytics through charts and session history, features calming ambient sounds, and maintains a distraction-free design that functions completely offline.

However, building a reliable timer proved challenging. Initial versions faced issues such as countdown freezes when the screen turned off, drift over long sessions, and inaccurate analytics data due to a lack of proper persistence. The key to a stable pomodoro timer lies in respecting how mobile operating systems handle apps. Instead of relying on Timer.periodic, which drifts and can freeze when the app is backgrounded or throttled, counting elapsed time against a fixed end point is more reliable.

By setting the end time when the session begins and calculating remaining time on each frame, the timer accurately reflects the actual duration. Additionally, using a Ticker for foreground and mounted widgets ensures the countdown repaints correctly, while avoiding leaks when the user navigates away. Sessions are modeled as a state machine, transitioning through focus, short breaks, and long breaks with transitions testable and UI logic kept simple.

Customizable durations are stored locally and validated, preventing unrealistic settings like a zero-minute break. To survive app suspensions and kills, local notifications are used to alert users at session start, which are then cancelled or allowed to fire as necessary. With these strategies, ZenPeace delivers a robust, user-friendly Pomodoro timer that works seamlessly in real-world conditions.