DevNotepad is a modern, lightweight mobile text editor for developers with an incremental delta-based version control system. Built with Kotlin, Jetpack Compose, and Room.
- ** Smart Syntax Highlighting** — Dynamic, regex-based real-time syntax highlighting for Kotlin (
.kt,.kts) and Markdown (.md) files. - ** Markdown Preview** — Dedicated read-only preview screen that beautifully renders Markdown elements (headings, bold, lists, code blocks, etc.) into styled text.
- ** Incremental Version Control** — Saves storage space by storing only the differences (deltas) between file saves using
java-diff-utils, rather than duplicating entire files for every version. - ** Auto-Save & Crash Recovery** — Background coroutines automatically back up your unsaved changes to a temporary cache every 10 seconds. Never lose your progress!
- ** Diff View (Version Comparison)** — Visually compare any two versions of a file with line-by-line additions and deletions highlighted (green for additions, red for deletions).
- ** Rollback Mechanism** — Easily restore any document to a previous state, safely rewinding your document history.
- ** In-Memory Undo/Redo** — Fully functional Undo/Redo stack for active editing sessions.
- ** Find & Replace** — Integrated, blazing-fast search bar to find and replace text across large files.
DevNotepad is built with modern Android development practices and libraries:
| Layer | Technology |
|---|---|
| Language | Kotlin (JDK 17) |
| UI Toolkit | Jetpack Compose (Material 3 Design Guidelines) |
| Database | Room Persistence Library (SQLite) |
| Diff Engine | java-diff-utils |
| Concurrency | Kotlin Coroutines & Flows |
| Architecture | MVVM (Single-Activity Architecture) |
| Local Storage | DataStore Preferences (for UI toggles & settings) |
DevNotepad employs an efficient versioning system to track file history without bloating storage:
- Base Version: The very first save of a file is stored completely.
- Deltas (Patches): Subsequent saves only compute and store the Unified Diff (patch) against the previous version.
- Reconstruction: When previewing or restoring an older version, the app starts from the Base Version and applies patches sequentially up to the requested version in memory.
- Database: All metadata (timestamps, file paths, versions, relationships) is securely managed via Room.
A built-in 10-second interval worker checks the editor buffer for unsaved changes. If the app crashes or is aggressively killed by the Android OS to reclaim memory, a Recovery Dialog greets the user upon reopening, allowing them to restore their lost work instantly.
Built entirely in Jetpack Compose using VisualTransformation, the editor styles text on the fly without modifying the underlying text data. It uses a priority-based tokenizer to ensure elements like strings and comments are styled accurately without conflicting with language keywords.
- Android Studio (Giraffe or newer recommended)
- JDK 17
- An Android Emulator or physical device running Android 8.0 (API 26) or higher.
- Clone the repository to your local machine:
git clone https://github.com/harithainduwara05/DevNotepad_MiniProject.git
- Open the project folder in Android Studio.
- Allow Gradle to sync all dependencies automatically.
- Run the app on your connected device/emulator, or build the APK via the command line:
./gradlew assembleDebug
app/src/main/java/com/devnotepad/editor/
├── DevNotepadApp.kt # Application class (Main entry point)
├── data/ # Data layer
│ ├── local/ # Room Database, DAOs, Entities
│ ├── model/ # Data classes & Enums (SyntaxMode, etc.)
│ └── repository/ # File & Database Repositories
├── ui/ # Presentation layer (Jetpack Compose)
│ ├── MainActivity.kt # Single-Activity entry point
│ ├── components/ # Reusable Compose Widgets (Toolbar, TextField)
│ ├── navigation/ # NavRoutes for Compose Navigation
│ ├── screens/ # App Screens (Editor, DiffView, History, Preview)
│ ├── theme/ # Material 3 Theme, Typography, Syntax Colors
│ └── viewmodel/ # ViewModels (EditorViewModel, HistoryViewModel)
└── highlight/ # Syntax Highlighting & Tokenization Logic
| Editor | Version History | Diff View | Markdown Preview |
|---|---|---|---|
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