I want to build a free music player for Windows and Android that uses local audio files only. The music itself would already be synchronized between my PC and phone, so the app mainly needs to synchronize playlist data. For example, if I add a song to a playlist on my PC and the same file exists on my phone, that playlist should update automatically and the song should be playable without manually exporting or importing playlists.
I already know Java and basic Python. I have considered using M3U files, but automatic import and export has been unreliable in the players I have tried. What language and framework would be a sensible choice for this project?
5 Answers
You do not necessarily need to build file synchronization and audio playback from scratch. Existing tools can synchronize the music directories, while your application handles playlist records and asks the operating system or a playback library to play local files. For a prototype, a simple HTTP API or synchronized JSON file may be easier than starting with a complex peer-to-peer system.
The language is less important than the design. Keep the audio files separate from the playlist synchronization: the files remain on each device, while the sync service only needs to transfer small playlist records. You could store those records in a synced folder, cloud storage, or a simple server.
Since you already know Java, Kotlin is probably the most efficient next step. It works natively with Android and can interoperate with your existing Java. Kotlin Multiplatform or Compose Multiplatform could let you share much of the application logic and possibly the UI between Android and Windows. Flutter with Dart is another practical cross-platform option if you prefer a single framework and do not mind learning a new language.
The tricky part is identifying the same track on two different devices. File paths will usually differ, so use a stable identifier such as a generated file hash or carefully chosen metadata like artist, album, title, and duration. A small database or structured playlist file can map that identifier to each device's local path. Once matching is reliable, the synchronization itself is relatively straightforward.
Java is also a valid choice, especially for Android, but desktop support and shared UI may require more separate work. Flutter is a reasonable alternative for one codebase, while Kotlin is a smoother transition from your current experience. I would prototype playlist matching and synchronization before investing heavily in the player interface or codec support.
That is what I had in mind. The music files are already synchronized with their normal folder structure; I mainly need a reliable way to keep the playlist data updated.