Android Book Reader

A lightweight reader: bookshelf, TXT / EPUB / MOBI / PDF, system speech (TTS) and audio export, on-device OCR, Chinese/English UI. E-books share one reading screen; PDF has its own.

中文

Features

Area	Capabilities
Bookshelf	Import TXT/PDF/EPUB/MOBI (and AZW, etc.) or folders; one-level shelves; bind folders; multi-select; search; backup/restore; reading history; long-press clear local records
E-books	TXT / EPUB / MOBI: large books show the first screen quickly, then prefetch the rest in the background
MOBI	Text body; view modes: text / single image / continuous strip; image-only books auto-enter image mode; improved UTF-8 Chinese MOBI
PDF	Continuous/single page, zoom, per-file crop, fast scroll, TOC, in-book links, TTS, tall-page tiled OCR (partial pages re-scanned), page-range audio export
TTS / export	System speech, rate control (e.g. 1×), sentence highlight, lock-screen continue, media controls; export MP3 / M4A / WAV
OCR	Gallery or camera; on-device; scanned PDFs (long pages split into strips)
Other	UI color themes (16); portrait / landscape lock (menu can stay open); fullscreen; app language; keep screen on / idle screen-off; volume-key page turn

Bookshelf

• Import files or folders; bind a folder (browse only, no copy)
• List style: compact rows, multi-select checkbox on the right
• Multi-select: move / remove (does not delete source files)
• Reading history with correct format labels (TXT / PDF / EPUB / MOBI…)
• Progress and bookmarks are remembered
• Long-press → Details (name, path, format, size, progress, last read, …)
• Long-press → Clear records: progress, bookmarks, EPUB/MOBI caches, PDF crop/OCR, etc. (shelf entry and source file kept)
• Returning from the reader refreshes progress on the shelf
• Backup / import shelves and progress (local only)
• Settings → Check for updates (download install from the release page)
• Settings → Appearance → Color theme (16 skins for chrome UI; reading page colors stay separate)
• Overflow: text-to-speech, OCR

E-book reading (TXT / EPUB / MOBI)

• Open: large books paint the first screen first, then prefetch in the background (EPUB/MOBI); restore position without flashing page 1
• Progress: EPUB/MOBI show chapter n/m + within-chapter %; TXT shows percentage
• TOC: auto-detect chapter titles; if empty or wrong, Custom TOC scan with wildcards (*, ? one char, x, xxx, xxxx) — e.g. 第x章 *, 第?回 *, Chapter x; saved per book and reopened for edit
• Reading style: background textures / solid color / imported image (full screen, adjustable opacity, solid underlay color, stretch or fit-center scale); text color presets + custom HSV; size and spacing; install custom fonts (long-press to remove); system default font (no bundled commercial typeface)
• TXT: auto or manual encoding; simplified↔traditional Chinese
• EPUB / MOBI styling (common features): bold / italic / underline / colors; block and inline images; in-book and external links; long-press image → gallery
• MOBI view modes (Style → View mode): Text (normal reading); Single image (one picture at a time, pinch-zoom, side-tap / swipe); Continuous strip (vertical image stream). Image-only MOBI auto-enters image mode; progress image n / total in image modes. Portrait ↔ landscape keeps zoom and horizontal pan ratio in continuous strip
• Text selection: long-press to select; handles at both ends to adjust; drag a handle to the top/bottom edge to auto-scroll and extend; copy / read-from-here menu
• Highlights & notes (TXT / EPUB / MOBI): Highlight from the selection menu; background or underline; optional note; note bubbles on the right; tap highlight or bubble to view/edit; Notes tab in the TOC sheet
• TOC / bookmarks / jump; battery and clock in the status bar; TOC opens scrolled to the current chapter; vertical list scroll does not steal horizontal tab swipe
• In-book search: live results, tap to jump
• Gestures: side-tap page turn, scroll; volume keys page turn (default on); left/right screen edge (10px) adjusts font size in 0.5sp steps; back can stop TTS only
• TTS: rate on the control bar (e.g. 1×); sentence highlight; lock-screen / background continue (below); sleep timer; when the bar closes, body text under it redraws immediately
• Export speech: full book or line range; MP3 / M4A / WAV + bitrate

PDF reading

• Continuous or single page; pinch-zoom; crop margins per file
• Progress % = scroll position / total content height (updates while scrolling inside tall pages)
• Fast scroll: right-edge thumb in continuous mode (drag to jump; shows while scrolling, hides ~1s after stop)
• TOC prepared in the background after open
• Links: page jump; external links need confirm; back / forward
• Select text when available; handles to adjust the range; OCR scanned pages (tall pages tiled; partial results re-scanned in strips; page range, cancelable)
• TTS / export after text or OCR; sentence highlight follows scroll and stays above the TTS bar; export by page range
• Side-tap page turn; center-tap opens the menu; orientation change can keep the 2×4 menu open; continuous mode keeps zoom and horizontal pan ratio when rotating

TTS & export

Item	Detail
System TTS	Engine, language, voice, rate label (e.g. 1×), highlight, sleep timer
Continuity	Prepares the next sentences to reduce gaps
Lock-screen	See below
Export	Build audio in chunks, then merge; prefer MP3, else M4A / WAV; live progress dialog
Bitrate	32–192 kbps for MP3/M4A
Standalone	Shelf ⋮ → Text to speech

Listening after lock / background

Goal: keep reading aloud after lock or switching apps, with notification and lock-screen controls.

What the app does (short)

• Shows a notification while speaking and tries to keep playback alive
• Pause / resume / prev / next sentence from the notification or lock screen
• Tries to ignore false “pause” events when the screen is off
• Bridges sentences and retries if something stalls

Leaving the reading screen does not stop TTS; progress can still be saved.

If your phone still kills playback

1. Allow notifications the first time you start TTS
2. Settings → Apps → this app → battery unrestricted
3. Lock the app in recents
4. Install a system TTS engine and a Chinese voice pack

Quick test

1. Open a book → play → confirm a “Speaking” notification
2. Lock the screen and listen for 1+ minutes
3. Use notification / lock controls

OCR

• Shelf ⋮ → OCR
• Fully on-device (no upload)
• Drag to select a region; scroll the full text

Requirements (dev)

Item	Value
Language	Kotlin
min Android	7.0
target Android	14
Build	Gradle + Android Gradle Plugin
JDK	17

Local setup

1. local.properties with SDK path (gitignored)
2. JDK 17
3. adb on PATH
4. Signing: keystore.properties + keystore (see example; do not commit secrets)

Quick start

cd reader
.\gradlew.bat assembleDebug
node build.js run
node build.js devices
node build.js release
node build.js apk

app/build/outputs/apk/debug/app-debug.apk
app/build/outputs/apk/release/reader{version}.apk
release/reader{version}.apk

See CHANGELOG.md for history.

Project layout (short)

reader/
├── app/src/main/
│   ├── assets/ocr/     # OCR models
│   ├── java/…/         # shelf, reading, PDF, TTS, OCR, settings
│   └── res/
├── documents/
├── build.js
├── CHANGELOG.md
└── README…

• TXT / EPUB / MOBI → e-book reading screen
• PDF → PDF reading screen
• TTS → system speech + notification / lock-screen controls

APK size (approx.)

Mostly OCR models and libraries, then PDF support; the rest is UI and app code. A small extra for MP3 export on 64-bit phones.

FAQ

No TTS audio

Install a system TTS engine and a Chinese voice pack; check volume.

TTS stops soon after lock

See Listening after lock / background: notifications, unrestricted battery, lock in recents. Another app may also be taking audio focus.

Garbled TXT

Auto-detect common encodings, or set encoding in the reader.

EPUB / MOBI slow or incomplete styling

Large books show the first screen first, then prefetch in the background. Only common styling is supported; complex layouts/tables may not match the desktop reader. DRM books will not open.

MOBI garbled Chinese text

Recent builds fix UTF-8 Chinese MOBI (e.g. mislabeled encoding or damaged PalmDOC HTML). Reopen the book or clear local records if an old parse cache persists.

No chapter list / wrong chapters

Open TOC → Custom TOC scan, pick a preset or enter a wildcard pattern (第x章 *, 001. style xxx. *, etc.), tap Apply. Pattern is remembered for that book.

MOBI is only images / comic

Use Style → View mode → Single image or Continuous strip, or open an image-only MOBI (auto image mode). Progress is image n / total.

Scanned PDF has no text

Use OCR scanned PDF pages; tall pages are split into strips. If only the top was recognized before, OCR again with “skip done” — partial pages are re-scanned. TTS/export need recognized text.

Select and copy text

Long-press a word (English expands to the whole word). Drag to extend, or use the handles after release. Drag a handle to the screen edge to scroll and extend. PDF needs extractable or OCR text.

PDF blank or squashed pages

Use the latest build; continuous mode previews while scrolling, then sharpens when idle. Reopen the book if it persists.

MP3 unavailable

Some emulators or non-64-bit devices fall back to M4A.

Links do nothing

PDF needs real links; EPUB needs links in the book. Use the TOC panel for plain-text contents.

License

MIT License
Copyright (c) 2026 whj

Full text: LICENSE.

• Covered by MIT: this project’s original Kotlin/Java source, layouts, and docs by the copyright holder
• Not covered by MIT: AndroidX / Material, PdfBox-Android, TensorFlow Lite, LAME/TAndroidLame, OCR model weights, etc. — see the third-party notice at the end of LICENSE

Notes

Personal/learning prototype. TTS uses the system engine; OCR never uploads images.