Transit Departure Board

Project roadmap

1. 01

   Choose the data source

   ~1h

   Pick a transit API that works for your city (many publish free real-time data), or, to start simply, host a JSON file with stops and departures (for example as a GitHub Gist). Write README.md describing the requests (search stops and departures for a stop) and the JSON fields you use, and the screens (saved stops, search, and departures). Create a Compose project and add Room, kotlinx.serialization and an HTTP client (such as Ktor or Retrofit). Done when: README.md describes the data source and screens.

2. 02

   Model the data

   ~1.5h

   Write @Serializable data classes for stops and departures, and a repository with functions to search stops and load departures, turning network and parsing errors into a clear error type. Create a Room entity for saved stops (id, name and an optional nickname) and one for the last departures loaded per stop with the time they were fetched. Done when: a unit test parses a saved JSON response, and Room saves a stop.

3. 03

   Save favorite stops

   ~1.5h

   Build a search screen that finds stops by name and saves one to favorites, and a home screen listing saved stops from a Room Flow, with swipe to delete and an empty state. Done when: stops can be found, saved and removed, and saved stops remain after restarting.

4. 04

   Show departures

   ~1.5h

   Build a departures screen that loads a stop's departures through a ViewModel, showing a loading state, then each departure's line, destination and minutes until it leaves (Now for under a minute, and a delay in red when the data includes it). Add pull-to-refresh and update the minutes every 30 seconds while the screen is open. Done when: departures appear and refresh for a saved stop.

5. 05

   Handle errors and offline use

   ~1.5h

   When loading fails, show the last departures saved in Room with a banner such as Offline, updated 12 minutes ago, removing departures that have already left, and a Retry button. Show a clear message when there's no saved data. Done when: in airplane mode, the app shows the last known departures with the banner instead of an error screen.

6. 06

   Test it

   ~1.5h

   Write tests: JSON parsing (valid and missing fields), the minutes-until-departure calculation, the ViewModel with a fake repository (loading, success, error and offline fallback), and Room DAO tests. Done when: all tests pass.

Resources

• DocsJetpack Compose tutorial
• DocsRoom documentation
• DocsViewModel overview
• Docskotlinx.serialization guide
• DocsKtor client documentation