Keyboard (lv_kb)

Overview

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

Modes

The Keyboards have two modes:

  • LV_KB_MODE_TEXT - Display letters, number, and special characters.

  • LV_KB_MODE_NUM - Display numbers, +/- sign, and decimal dot.

To set the mode, use lv_kb_set_mode(kb, mode). The default is LV_KB_MODE_TEXT.

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_kb_set_ta(kb, ta).

The assigned text area’s cursor can be managed by the keyboard: when the keyboard is assigned, the previous text area’s cursor will be hidden and the new one will be shown. When the keyboard is closed by the Ok or Close buttons, the cursor also will be hidden. The cursor manager feature is enabled by lv_kb_set_cursor_manage(kb, true). The default is not managed.

New Keymap

You can specify a new map (layout) for the keyboard with lv_kb_set_map(kb, map) and lv_kb_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.

  • SYMBOL_CLOSE - Close.

  • LV_SYMBOL_LEFT - Move the cursor left.

  • LV_SYMBOL_RIGHT - Move the cursor right.

  • “ABC” - Load the uppercase map.

  • “abc” - Load the lower case map.

  • “Enter” - New line.

  • “Bkps” - Delete on the left.

Styles

The Keyboard work with 6 styles: a background and 5 button styles for each state. You can set the styles with lv_kb_set_style(btn, LV_KB_STYLE_..., &style). The background and the buttons use the style.body properties. The labels use the style.text properties of the buttons’ styles.

  • LV_KB_STYLE_BG - Background style. Uses all style.body properties including padding Default: lv_style_pretty.

  • LV_KB_STYLE_BTN_REL - Style of the released buttons. Default: lv_style_btn_rel.

  • LV_KB_STYLE_BTN_PR - Style of the pressed buttons. Default: lv_style_btn_pr.

  • LV_KB_STYLE_BTN_TGL_REL - Style of the toggled released buttons. Default: lv_style_btn_tgl_rel.

  • LV_KB_STYLE_BTN_TGL_PR - Style of the toggled pressed buttons. Default: lv_style_btn_tgl_pr.

  • LV_KB_STYLE_BTN_INA - Style of the inactive buttons. Default: lv_style_btn_ina.

Events

Besides the Generic events, the following Special events are sent by the keyboards:

  • 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_APPLY - The Ok button is clicked.

  • LV_EVENT_CANCEL - The Close button is clicked.

The keyboard has a default event handler callback called lv_kb_def_event_cb. It handles the button pressing, map changing, the assigned text area, etc. You can completely replace it with your custom event handler however, you can call lv_kb_def_event_cb at the beginning of your event handler to handle the same things as before.

Learn more about Events.

Keys

The following Keys are processed by the buttons:

  • 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

C

Keyboard with text area

Keyboard example in LittlevGL

code

#include "lvgl/lvgl.h"

void lv_ex_kb_1(void)
{
    /*Create styles for the keyboard*/
    static lv_style_t rel_style, pr_style;

    lv_style_copy(&rel_style, &lv_style_btn_rel);
    rel_style.body.radius = 0;
    rel_style.body.border.width = 1;

    lv_style_copy(&pr_style, &lv_style_btn_pr);
    pr_style.body.radius = 0;
    pr_style.body.border.width = 1;

    /*Create a keyboard and apply the styles*/
    lv_obj_t *kb = lv_kb_create(lv_scr_act(), NULL);
    lv_kb_set_cursor_manage(kb, true);
    lv_kb_set_style(kb, LV_KB_STYLE_BG, &lv_style_transp_tight);
    lv_kb_set_style(kb, LV_KB_STYLE_BTN_REL, &rel_style);
    lv_kb_set_style(kb, LV_KB_STYLE_BTN_PR, &pr_style);

    /*Create a text area. The keyboard will write here*/
    lv_obj_t *ta = lv_ta_create(lv_scr_act(), NULL);
    lv_obj_align(ta, NULL, LV_ALIGN_IN_TOP_MID, 0, 10);
    lv_ta_set_text(ta, "");

    /*Assign the text area to the keyboard*/
    lv_kb_set_ta(kb, ta);
}

MicroPython

Keyboard with text area

Keyboard example in LittlevGL with MicroPython

code

# Create styles for the keyboard
rel_style = lv.style_t()
pr_style  = lv.style_t()

lv.style_copy(rel_style, lv.style_btn_rel)
rel_style.body.radius = 0
rel_style.body.border.width = 1

lv.style_copy(pr_style, lv.style_btn_pr)
pr_style.body.radius = 0
pr_style.body.border.width = 1

# Create a keyboard and apply the styles
kb = lv.kb(lv.scr_act())
kb.set_cursor_manage(True)
kb.set_style(lv.kb.STYLE.BG, lv.style_transp_tight)
kb.set_style(lv.kb.STYLE.BTN_REL, rel_style)
kb.set_style(lv.kb.STYLE.BTN_PR, pr_style)

# Create a text area. The keyboard will write here
ta = lv.ta(lv.scr_act())
ta.align(None, lv.ALIGN.IN_TOP_MID, 0, 10)
ta.set_text("")

# Assign the text area to the keyboard
kb.set_ta(ta)

API

Typedefs

typedef uint8_t lv_kb_mode_t
typedef uint8_t lv_kb_style_t

Enums

enum [anonymous]

Current keyboard mode.

Values:

enumerator LV_KB_MODE_TEXT
enumerator LV_KB_MODE_NUM
enumerator LV_KB_MODE_TEXT_UPPER
enum [anonymous]

Values:

enumerator LV_KB_STYLE_BG
enumerator LV_KB_STYLE_BTN_REL
enumerator LV_KB_STYLE_BTN_PR
enumerator LV_KB_STYLE_BTN_TGL_REL
enumerator LV_KB_STYLE_BTN_TGL_PR
enumerator LV_KB_STYLE_BTN_INA

Functions

lv_obj_t *lv_kb_create(lv_obj_t *par, const lv_obj_t *copy)

Create a keyboard objects

Return

pointer to the created keyboard

Parameters

  • par: pointer to an object, it will be the parent of the new keyboard

  • copy: pointer to a keyboard object, if not NULL then the new object will be copied from it

void lv_kb_set_ta(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_kb_set_mode(lv_obj_t *kb, lv_kb_mode_t mode)

Set a new a mode (text or number map)

Parameters

  • kb: pointer to a Keyboard object

  • mode: the mode from ‘lv_kb_mode_t’

void lv_kb_set_cursor_manage(lv_obj_t *kb, bool en)

Automatically hide or show the cursor of the current Text Area

Parameters

  • kb: pointer to a Keyboard object

  • en: true: show cursor on the current text area, false: hide cursor

void lv_kb_set_map(lv_obj_t *kb, const char *map[])

Set a new map for the keyboard

Parameters

  • kb: pointer to a Keyboard object

  • map: pointer to a string array to describe the map. See ‘lv_btnm_set_map()’ for more info.

void lv_kb_set_ctrl_map(lv_obj_t *kb, const lv_btnm_ctrl_t ctrl_map[])

Set the button control map (hidden, disabled etc.) for the keyboard. The control map array will be copied and so may be deallocated after this function returns.

Parameters

  • kb: pointer to a keyboard object

  • ctrl_map: pointer to an array of lv_btn_ctrl_t control bytes. See: lv_btnm_set_ctrl_map for more details.

void lv_kb_set_style(lv_obj_t *kb, lv_kb_style_t type, const lv_style_t *style)

Set a style of a keyboard

Parameters

  • kb: pointer to a keyboard object

  • type: which style should be set

  • style: pointer to a style

lv_obj_t *lv_kb_get_ta(const lv_obj_t *kb)

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

Return

pointer to the assigned Text Area object

Parameters

  • kb: pointer to a Keyboard object

lv_kb_mode_t lv_kb_get_mode(const lv_obj_t *kb)

Set a new a mode (text or number map)

Return

the current mode from ‘lv_kb_mode_t’

Parameters

  • kb: pointer to a Keyboard object

bool lv_kb_get_cursor_manage(const lv_obj_t *kb)

Get the current cursor manage mode.

Return

true: show cursor on the current text area, false: hide cursor

Parameters

  • kb: pointer to a Keyboard object

const char **lv_kb_get_map_array(const lv_obj_t *kb)

Get the current map of a keyboard

Return

the current map

Parameters

  • kb: pointer to a keyboard object

const lv_style_t *lv_kb_get_style(const lv_obj_t *kb, lv_kb_style_t type)

Get a style of a keyboard

Return

style pointer to a style

Parameters

  • kb: pointer to a keyboard object

  • type: which style should be get

void lv_kb_def_event_cb(lv_obj_t *kb, lv_event_t event)

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 be called from it to handle the button clicks

Parameters

  • kb: pointer to a keyboard

  • event: the triggering event

struct lv_kb_ext_t

Public Members

lv_btnm_ext_t btnm
lv_obj_t *ta
lv_kb_mode_t mode
uint8_t cursor_mng