Checkbox (lv_checkbox)¶

Overview¶

The Checkbox object is created from a "tick box" and a label. When the Chackbox is clicked the tick box is toggled.

Parts and Styles¶

LV_PART_MAIN The is the background of the Checkbox and it uses the text and all the typical backround style properties. pad_column adjusts the spacing between the tickbox and the label
LV_PART_INDICATOR The "tick box" is a square that uses all the typical backround style properties. By default its size is equal to the height of the main part's font. Padding properties make the tick box larger in the respective directions.

The Checkbox is added to the default group (if it is set).

Usage¶

Text¶

The text can be modified with the lv_checkbox_set_text(cb, "New text") function and will be dynamically allocated.

To set a static text, use lv_checkbox_set_static_text(cb, txt). This way, only a pointer to txt will be stored. The text then shouldn't be deallocated while the checkbox exists.

Check, uncheck, disable¶

You can manually check, un-check, and disable the Checkbox by using the common state add/clear function:

lv_obj_add_state(cb, LV_STATE_CHECKED);   /*Make the chekbox checked*/
lv_obj_clear_state(cb, LV_STATE_CHECKED); /*MAke the checkbox unchecked*/
lv_obj_add_state(cb, LV_STATE_CHECKED | LV_STATE_DISABLED); /*Make the checkbox checked and disabled*/

Events¶

LV_EVENT_VALUE_CHANGED Sent when the checkbox is toggled.
LV_EVENT_DRAW_PART_BEGIN and LV_EVENT_DRAW_PART_END are sent for both main and indicator parts to allow hooking the drawing. For more detail on the main part see the Base object's documentation. For the indicator the following fields are used: clip_area, draw_area, rect_dsc, part.

Learn more about Events.

Keys¶

The following Keys are processed by the 'Buttons':

LV_KEY_RIGHT/UP Go to toggled state if toggling is enabled
LV_KEY_LEFT/DOWN Go to non-toggled state if toggling is enabled
LV_KEY_ENTER Clicks the checkbox and toggles it

Note that, as usual, the state of LV_KEY_ENTER is translated to LV_EVENT_PRESSED/PRESSING/RELEASED etc.

Learn more about Keys.

Example¶

C¶

Simple Checkboxes¶

#include "../../lv_examples.h"
#if LV_USE_CHECKBOX && LV_BUILD_EXAMPLES

static void event_handler(lv_event_t * e)
{
    lv_event_code_t code = lv_event_get_code(e);
    lv_obj_t * obj = lv_event_get_target(e);
    if(code == LV_EVENT_VALUE_CHANGED) {
        const char * txt = lv_checkbox_get_text(obj);
        const char * state = lv_obj_get_state(obj) & LV_STATE_CHECKED ? "Checked" : "Unchecked";
        LV_LOG_USER("%s: %s", txt, state);
    }
}

void lv_example_checkbox_1(void)
{
    lv_obj_set_flex_flow(lv_scr_act(), LV_FLEX_FLOW_COLUMN);
    lv_obj_set_flex_align(lv_scr_act(), LV_FLEX_ALIGN_CENTER, LV_FLEX_ALIGN_START, LV_FLEX_ALIGN_CENTER);

    lv_obj_t * cb;
    cb = lv_checkbox_create(lv_scr_act());
    lv_checkbox_set_text(cb, "Apple");
    lv_obj_add_event_cb(cb, event_handler, LV_EVENT_ALL, NULL);

    cb = lv_checkbox_create(lv_scr_act());
    lv_checkbox_set_text(cb, "Banana");
    lv_obj_add_state(cb, LV_STATE_CHECKED);
    lv_obj_add_event_cb(cb, event_handler, LV_EVENT_ALL, NULL);

    cb = lv_checkbox_create(lv_scr_act());
    lv_checkbox_set_text(cb, "Lemon");
    lv_obj_add_state(cb, LV_STATE_DISABLED);
    lv_obj_add_event_cb(cb, event_handler, LV_EVENT_ALL, NULL);

    cb = lv_checkbox_create(lv_scr_act());
    lv_obj_add_state(cb, LV_STATE_CHECKED | LV_STATE_DISABLED);
    lv_checkbox_set_text(cb, "Melon\nand a new line");
    lv_obj_add_event_cb(cb, event_handler, LV_EVENT_ALL, NULL);

    lv_obj_update_layout(cb);
}

#endif

MicroPython¶

No examples yet.

API¶

Functions

lv_obj_t *lv_checkbox_create(lv_obj_t *parent)¶

Create a check box object

Parameters: parent -- pointer to an object, it will be the parent of the new button
Returns: pointer to the created check box

void lv_checkbox_set_text(lv_obj_t *obj, const char *txt)¶

Set the text of a check box. txt will be copied and may be deallocated after this function returns.

Parameters

cb -- pointer to a check box
txt -- the text of the check box. NULL to refresh with the current text.

void lv_checkbox_set_text_static(lv_obj_t *obj, const char *txt)¶

Set the text of a check box. txt must not be deallocated during the life of this checkbox.

Parameters

cb -- pointer to a check box
txt -- the text of the check box. NULL to refresh with the current text.

const char *lv_checkbox_get_text(const lv_obj_t *obj)¶

Get the text of a check box

Parameters: cb -- pointer to check box object
Returns: pointer to the text of the check box

Variables

const lv_obj_class_t lv_checkbox_class¶

struct lv_checkbox_t¶

Public Members

lv_obj_t obj¶

char *txt¶

uint32_t static_txt¶