ndg/lib/lvgl/docs/widgets/extra/keyboard.md

Keyboard (lv_keyboard)

Overview

The Keyboard object is a special Button matrix with predefined keymaps and other features to realize a virtual keyboard to write texts into a Text area.

Parts and Styles

Similarly to Button matrices Keyboards consist of 2 part:

• LV_PART_MAIN The main part. Uses all the typical background properties
• LV_PART_ITEMS The buttons. Also uses all typical background properties as well as the text properties.

Usage

Modes

The Keyboards have the following modes:

• LV_KEYBOARD_MODE_TEXT_LOWER Display lower case letters
• LV_KEYBOARD_MODE_TEXT_UPPER Display upper case letters
• LV_KEYBOARD_MODE_TEXT_SPECIAL Display special characters
• LV_KEYBOARD_MODE_NUMBER Display numbers, +/- sign, and decimal dot
• LV_KEYBOARD_MODE_USER_1 through LV_KEYBOARD_MODE_USER_4 User-defined modes.

The TEXT modes' layout contains buttons to change mode.

To set the mode manually, use lv_keyboard_set_mode(kb, mode). The default mode is LV_KEYBOARD_MODE_TEXT_UPPER.

Assign Text area

You can assign a Text area to the Keyboard to automatically put the clicked characters there. To assign the text area, use lv_keyboard_set_textarea(kb, ta).

Key Popovers

To enable key popovers on press, like on common Android and iOS keyboards, use lv_keyboard_set_popovers(kb, true). The default control maps are preconfigured to only show the popovers on keys that produce a symbol and not on e.g. space. If you use a custom keymap, set the LV_BTNMATRIX_CTRL_POPOVER flag for all keys that you want to show a popover.

Note that popovers for keys in the top row will draw outside the widget boundaries. To account for this, reserve extra free space on top of the keyboard or ensure that the keyboard is added after any widgets adjacent to its top boundary so that the popovers can draw over those.

The popovers currently are merely a visual effect and don't allow selecting additional characters such as accents yet.

New Keymap

You can specify a new map (layout) for the keyboard with lv_keyboard_set_map(kb, map) and lv_keyboard_set_ctrl_map(kb, ctrl_map). Learn more about the Button matrix object. Keep in mind that using following keywords will have the same effect as with the original map:

• LV_SYMBOL_OK Apply.
• LV_SYMBOL_CLOSE or LV_SYMBOL_KEYBOARD Close.
• LV_SYMBOL_BACKSPACE Delete on the left.
• LV_SYMBOL_LEFT Move the cursor left.
• LV_SYMBOL_RIGHT Move the cursor right.
• LV_SYMBOL_NEW_LINE New line.
• "ABC" Load the uppercase map.
• "abc" Load the lower case map.
• "1#" Load the lower case map.

Events

• LV_EVENT_VALUE_CHANGED Sent when the button is pressed/released or repeated after long press. The event data is set to the ID of the pressed/released button.
• LV_EVENT_READY - The Ok button is clicked.
• LV_EVENT_CANCEL - The Close button is clicked.

The keyboard has a default event handler callback called lv_keyboard_def_event_cb, which handles the button pressing, map changing, the assigned text area, etc. You can remove it and replace it with a custom event handler if you wish.

.. note::
   In 8.0 and newer, adding an event handler to the keyboard does not remove the default event handler.
   This behavior differs from v7, where adding an event handler would always replace the previous one.

Learn more about Events.

Keys

• LV_KEY_RIGHT/UP/LEFT/RIGHT To navigate among the buttons and select one.
• LV_KEY_ENTER To press/release the selected button.

Learn more about Keys.

Examples

.. include:: ../../../examples/widgets/keyboard/index.rst

API

.. doxygenfile:: lv_keyboard.h
  :project: lvgl