lv_example_slider_3.c

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

static void slider_event_cb(lv_event_t * e);

/**
 * Show the current value when the slider is pressed by extending the drawer
 *
 */
void lv_example_slider_3(void)
{
    /*Create a slider in the center of the display*/
    lv_obj_t * slider;
    slider = lv_slider_create(lv_screen_active());
    lv_obj_center(slider);

    lv_slider_set_mode(slider, LV_SLIDER_MODE_RANGE);
    lv_slider_set_value(slider, 70, LV_ANIM_OFF);
    lv_slider_set_left_value(slider, 20, LV_ANIM_OFF);

    lv_obj_add_event_cb(slider, slider_event_cb, LV_EVENT_ALL, NULL);
    lv_obj_refresh_ext_draw_size(slider);
}

static void slider_event_cb(lv_event_t * e)
{
    lv_event_code_t code = lv_event_get_code(e);
    lv_obj_t * obj = lv_event_get_target(e);

    /*Provide some extra space for the value*/
    if(code == LV_EVENT_REFR_EXT_DRAW_SIZE) {
        lv_event_set_ext_draw_size(e, 50);
    }
    else if(code == LV_EVENT_DRAW_MAIN_END) {
        if(!lv_obj_has_state(obj, LV_STATE_PRESSED)) return;

        lv_slider_t * slider = (lv_slider_t *) obj;
        const lv_area_t * indic_area = &slider->bar.indic_area;
        char buf[16];
        lv_snprintf(buf, sizeof(buf), "%d - %d", (int)lv_slider_get_left_value(obj), (int)lv_slider_get_value(obj));

        lv_point_t label_size;
        lv_text_get_size(&label_size, buf, LV_FONT_DEFAULT, 0, 0, LV_COORD_MAX, 0);
        lv_area_t label_area;
        label_area.x1 = 0;
        label_area.x2 = label_size.x - 1;
        label_area.y1 = 0;
        label_area.y2 = label_size.y - 1;

        lv_area_align(indic_area, &label_area, LV_ALIGN_OUT_TOP_MID, 0, -10);

        lv_draw_label_dsc_t label_draw_dsc;
        lv_draw_label_dsc_init(&label_draw_dsc);
        label_draw_dsc.color = lv_color_hex3(0x888);
        label_draw_dsc.text = buf;
        label_draw_dsc.text_local = true;
        lv_layer_t * layer = lv_event_get_layer(e);
        lv_draw_label(layer, &label_draw_dsc, &label_area);
    }
}

#endif