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Hibi 「日々」

An app for Android designed to aid your Japanese learning through keeping a journal.


  • Add entries at any date and time
  • Search for words through right from the editing screen without having to switch app
  • Save new words used in an entry
  • Tag entries (e.g. Holiday, Day Out, Birthday)
  • Add entries to books (e.g. Trip to Tokyo 2018, Trip to Shirakawa-go 2019)
  • Add locations to entries
  • Add images to entries
  • Search your entries based on date, content, location, tags or books
  • Daily reminder to add an entry
  • Ability to backup and restore your data
  • Dark theme and Light theme
  • Easily see entries made on this day last month, and in previous years, using the Throwback feature

Tech and Architecture

Architecture Diagram

Hibi is written entirely in Kotlin and employs a single activity MVVM architecture pattern using AndroidX View Model components. The activity contains a single NavHostFragment, part of the AndroidX Navigation Components, which hosts all other fragments such as the MainScreenFragment. Each fragment observes data in a View Model which may retrieve data from various repositories and API services and properly format it for display. All business logic is handled in the View Models and fragments are kept as minimal as possible (only having code for setting up Observers, click listeners, etc...). Data is stored using a Room database and queries are provided in a DAO in the form of functions. Data is then retrieved asynchronously within repositories using Kotlin coroutines and LiveData. Kodein is used for dependency injection due to it's native support for Kotlin and it's ease of writing. API calls are made using Retrofit and then converted into Kotlin objects using Moshi. Design inspired by Material Design and implemented using Material Components for Android.


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