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, LV_KEYBOARD_MODE_..., kb_map, kb_ctrl);. See the Button matrix for more information about creating new maps a ctrls.

Keep in mind that using following keywords will have the same effect as with the original map:

  • LV_SYMBOL_OK Send LV_EVENT_RADY to the assigend Text area.

  • LV_SYMBOL_CLOSE or LV_SYMBOL_KEYBOARD Send LV_EVENT_CANCEL to the assigend Text area.

  • 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

API

Typedefs

typedef uint8_t lv_keyboard_mode_t

Enums

enum [anonymous]

Current keyboard mode.

Values:

enumerator LV_KEYBOARD_MODE_TEXT_LOWER
enumerator LV_KEYBOARD_MODE_TEXT_UPPER
enumerator LV_KEYBOARD_MODE_SPECIAL
enumerator LV_KEYBOARD_MODE_NUMBER
enumerator LV_KEYBOARD_MODE_USER_1
enumerator LV_KEYBOARD_MODE_USER_2
enumerator LV_KEYBOARD_MODE_USER_3
enumerator LV_KEYBOARD_MODE_USER_4

Functions

lv_obj_t *lv_keyboard_create(lv_obj_t *parent)

Create a Keyboard object

Parameters

parent -- pointer to an object, it will be the parent of the new keyboard

Returns

pointer to the created keyboard

void lv_keyboard_set_textarea(lv_obj_t *kb, lv_obj_t *ta)

Assign a Text Area to the Keyboard. The pressed characters will be put there.

Parameters
  • kb -- pointer to a Keyboard object

  • ta -- pointer to a Text Area object to write there

void lv_keyboard_set_mode(lv_obj_t *kb, lv_keyboard_mode_t mode)

Set a new a mode (text or number map)

Parameters
  • kb -- pointer to a Keyboard object

  • mode -- the mode from 'lv_keyboard_mode_t'

void lv_keyboard_set_popovers(lv_obj_t *kb, bool en)

Show the button title in a popover when pressed.

Parameters
  • kb -- pointer to a Keyboard object

  • en -- whether "popovers" mode is enabled

void lv_keyboard_set_map(lv_obj_t *kb, lv_keyboard_mode_t mode, const char *map[], const lv_btnmatrix_ctrl_t ctrl_map[])

Set a new map for the keyboard

Parameters
  • kb -- pointer to a Keyboard object

  • mode -- keyboard map to alter 'lv_keyboard_mode_t'

  • map -- pointer to a string array to describe the map. See 'lv_btnmatrix_set_map()' for more info.

lv_obj_t *lv_keyboard_get_textarea(const lv_obj_t *kb)

Assign a Text Area to the Keyboard. The pressed characters will be put there.

Parameters

kb -- pointer to a Keyboard object

Returns

pointer to the assigned Text Area object

lv_keyboard_mode_t lv_keyboard_get_mode(const lv_obj_t *kb)

Set a new a mode (text or number map)

Parameters

kb -- pointer to a Keyboard object

Returns

the current mode from 'lv_keyboard_mode_t'

bool lv_btnmatrix_get_popovers(const lv_obj_t *obj)

Tell whether "popovers" mode is enabled or not.

Parameters

kb -- pointer to a Keyboard object

Returns

true: "popovers" mode is enabled; false: disabled

static inline const char **lv_keyboard_get_map_array(const lv_obj_t *kb)

Get the current map of a keyboard

Parameters

kb -- pointer to a keyboard object

Returns

the current map

static inline uint16_t lv_keyboard_get_selected_btn(const lv_obj_t *obj)

Get the index of the lastly "activated" button by the user (pressed, released, focused etc) Useful in the event_cb to get the text of the button, check if hidden etc.

Parameters

obj -- pointer to button matrix object

Returns

index of the last released button (LV_BTNMATRIX_BTN_NONE: if unset)

static inline const char *lv_keyboard_get_btn_text(const lv_obj_t *obj, uint16_t btn_id)

Get the button's text

Parameters
  • obj -- pointer to button matrix object

  • btn_id -- the index a button not counting new line characters.

Returns

text of btn_index` button

void lv_keyboard_def_event_cb(lv_event_t *e)

Default keyboard event to add characters to the Text area and change the map. If a custom event_cb is added to the keyboard this function can be called from it to handle the button clicks

Parameters
  • kb -- pointer to a keyboard

  • event -- the triggering event

Variables

const lv_obj_class_t lv_keyboard_class
struct lv_keyboard_t

Public Members

lv_btnmatrix_t btnm
lv_obj_t *ta
lv_keyboard_mode_t mode
uint8_t popovers