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Alejandro Guerrero 2026-09-27 17:21:39 +02:00
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49
libraries/lvgl/examples/others/msg/lv_example_msg_1.c Normal file
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#include "../../lv_examples.h"
#if LV_USE_MSG && LV_USE_SLIDER && LV_USE_LABEL && LV_BUILD_EXAMPLES
/*Define a message ID*/
#define MSG_NEW_TEMPERATURE 1
static void slider_event_cb(lv_event_t * e);
static void label_event_cb(lv_event_t * e);
/**
* A slider sends a message on value change and a label display's that value
*/
void lv_example_msg_1(void)
{
/*Create a slider in the center of the display*/
lv_obj_t * slider = lv_slider_create(lv_scr_act());
lv_obj_center(slider);
lv_obj_add_event_cb(slider, slider_event_cb, LV_EVENT_VALUE_CHANGED, NULL);
/*Create a label below the slider*/
lv_obj_t * label = lv_label_create(lv_scr_act());
lv_obj_add_event_cb(label, label_event_cb, LV_EVENT_MSG_RECEIVED, NULL);
lv_label_set_text(label, "0%");
lv_obj_align(label, LV_ALIGN_CENTER, 0, 30);
/*Subscribe the label to a message. Also use the user_data to set a format string here.*/
lv_msg_subsribe_obj(MSG_NEW_TEMPERATURE, label, "%d °C");
}
static void slider_event_cb(lv_event_t * e)
{
/*Notify all subscribers (only the label now) that the slider value has been changed*/
lv_obj_t * slider = lv_event_get_target(e);
int32_t v = lv_slider_get_value(slider);
lv_msg_send(MSG_NEW_TEMPERATURE, &v);
}
static void label_event_cb(lv_event_t * e)
{
lv_obj_t * label = lv_event_get_target(e);
lv_msg_t * m = lv_event_get_msg(e);
const char * fmt = lv_msg_get_user_data(m);
const int32_t * v = lv_msg_get_payload(m);
lv_label_set_text_fmt(label, fmt, *v);
}
#endif