lvgl/examples/get_started/lv_example_get_started_3.c

#include "../../lvgl.h"
#if LV_BUILD_EXAMPLES && LV_USE_SLIDER

static lv_obj_t * label;

static void slider_event_cb(lv_obj_t * slider, lv_event_t event)
{
    if(event == LV_EVENT_VALUE_CHANGED) {
        /*Refresh the text*/
        lv_label_set_text_fmt(label, "%d", lv_slider_get_value(slider));
        lv_obj_align(label, slider, LV_ALIGN_OUT_TOP_MID, 0, -15);    /*Align below the slider*/
    }
}

/**
 * Create a slider and write its value on a label.
 */
void lv_example_get_started_3(void)
{
    /*Create a slider in the center of the display*/
    lv_obj_t * slider = lv_slider_create(lv_scr_act(), NULL);
    lv_obj_set_width(slider, 200);                        /*Set the width*/
    lv_obj_align(slider, NULL, LV_ALIGN_CENTER, 0, 0);    /*Align to the center of the parent (screen)*/
    lv_obj_add_event_cb(slider, slider_event_cb, NULL);         /*Assign an event function*/

    /*Create a label below the slider*/
    label = lv_label_create(lv_scr_act(), NULL);
    lv_label_set_text(label, "0");
    lv_obj_align(label, slider, LV_ALIGN_OUT_TOP_MID, 0, -15);    /*Align below the slider*/
}

#endif