An Android reader app committed to improving reading experience.

PDF, EPUB, MOBI, CBZ, FB2, XPS, TXT, HTML, OFFICE(DOCX, XLSX, PPTX), and ZIP/GZIP package of previous documents are supported.

• Flip Vertical

  Flip Vertical and Flip Horizontal modes are both supported.

• RtL Text

  In top-to-bottom, right-to-left script (TB-RL or vertical), writing starts from the top of the page and continues to the bottom, proceeding from right to left for new lines, pages numbered from right to left (from Wikipedia). The RtL Text mode can be applied to books of East Asian languages, including classical Chinese, Japanese and Korean.

• Single Column

  Some PDF books were scanned in a way that left and right pages were put in one image, resulting in a so called dual-spread page. In the scenario, Single Column mode plays a role. It splits a dual-spread page into two pages.

  Single Column mode can also be a conveniency for magazines and scientific papers with two columns in a page.

  In Single Column mode, all pages except first and last page are splitted.

• Continuous scroll

  Continuous scroll has been perfectly implemented in all scenarios.

• Lock Stray

  When flinging or scrolling a zoomed page, it can hardly move in straight horizontal/vertical direction, and be annoying reading experience. Here the Lock Stray mode will make a help.

• Crop Margin

  Crop page margins to get more efficient reading space. All document types are supported.

• Focus

  Focus mode will keep page position across zoomed pages. On moving to a definite page, that is, tapping to next/prev page, choosing on Toc/bookmark table, navigating through links or text search, and skimming on page slider, it will present visible content area of new page in same position as the old one. Note that scroll/fling operation is an exception.

  On entering Focus mode, current page will zoom automatically to match screen in shorter dimension and center itself.

• Smart Focus

  With scanned PDF books, content area scarcely appear exactly centered in a page. More probable it inclines toward left or right side. Smart Focus deals with the scenario. By adjusting the position of even or odd pages accordingly, it makes Focus mode behave smartly.

  Smart Focus must work with Focus mode to make sense.

• Text Select

  Text Select toolbar is implemented, along with select point magnifier. Operations of copy, share, translate, and more are supported.

  During text selecting, page navigation operations still work as ever.

• Color Palette

  Color Palette are for maxmium legibility and are ideal for reducing eye strain conductive to focused reading.

• Font Size

  Font Size function works in flowable documents, like EPUBs.

• Options

  Document Options are applied to current document. Global Options are applied to all documents. Document Options priorizes over Global Options.

• Contents

  Contents menu includes following two functions:

• Table of Contents

  Table of Contents will show up if the document has one. It supports multi-level headings, heading collapsing and expanding. It always keep sync with current page.

• Bookmarks

  Bookmarks works across reading sessions. Double tap on a page to create a bookmark.

• Activate Links

  Activate Links and make them navigable.

• Search

  Full text Search and navigate through search results.

• Share Book

  Share current book to Contacts or other apps.

• Scrollable Toobar

  Scrollable Toolbar can accommodate more buttons for extended funtions. To avoid overlapped with status bar, the Toolbar can be moved to bottom.

• Pros and Cons

  In case of big books(thousands of pages), PDFs were opened very quick, and EPUBs badly slow.

• A function button will show up in Toolbar when the corresponding function is applicable, otherwise it will be hidden.
• Long press on a Toolbar button, to show function tooltip.
• Tap in left/top/right/bottom side, to move a page forward or backward.
• Tap in middle, to show/hide Toolbar and Page Indicator
• Press down and move, to scrol page view
• Press down two fingers and move one, to zoom in/out page view
• Fling horizontally/vertically, to Scroll Continuously
• Under the combination of Flip Horizontal and not Rtl Text mode, or of Flip Vertical and Rtl Text mode, and scroll to where between two pages, it will slide slowly into the near page. This behavior guarantees that any page contents will not be cut off.
• Under the combination of Flip Horizontal and Rtl Text mode, or of Flip Vertical and not Rtl Text mode, pages can stay at any position which will never cut off page contents. This behavior makes reading across two pages comfortably.
• Long press on text, to begin text select.
• Double tap to create a Bookmark on current page.
• In Contents window, swipe left/right to switch Contents view or close.
• In Help window, swipe right to close.
• All reading states as of page scale, position, last read page number, as well as all enable button states are remembered across reading sessions for per book.
• In general, to get the best reading experience mutiple function modes can be employed, adding appropriate screen orientation if needed.

• MuPDF Android Viewer and developers
• MarkedView for help document rendering

• GitHub repo: https://github.com/elementdavv/chaka
• Email: elementdavv@hotmail.com
• Telegram: @elementdavv
• X(Twitter): @elementdavv

If you enjoy Chaka, consider supporting or hiring the maintainer @elementdavv