1 #include "../../lv_examples.h"
2 #if LV_USE_MSG && LV_USE_SLIDER && LV_USE_LABEL && LV_BUILD_EXAMPLES
3
4 /*Define a message ID*/
5 #define MSG_NEW_TEMPERATURE 1
6
7 static void slider_event_cb(lv_event_t * e);
8 static void label_event_cb(lv_event_t * e);
9
10 /**
11 * A slider sends a message on value change and a label display's that value
12 */
lv_example_msg_1(void)13 void lv_example_msg_1(void)
14 {
15 /*Create a slider in the center of the display*/
16 lv_obj_t * slider = lv_slider_create(lv_scr_act());
17 lv_obj_center(slider);
18 lv_obj_add_event_cb(slider, slider_event_cb, LV_EVENT_VALUE_CHANGED, NULL);
19
20 /*Create a label below the slider*/
21 lv_obj_t * label = lv_label_create(lv_scr_act());
22 lv_obj_add_event_cb(label, label_event_cb, LV_EVENT_MSG_RECEIVED, NULL);
23 lv_label_set_text(label, "0%");
24 lv_obj_align(label, LV_ALIGN_CENTER, 0, 30);
25
26 /*Subscribe the label to a message. Also use the user_data to set a format string here.*/
27 lv_msg_subsribe_obj(MSG_NEW_TEMPERATURE, label, "%d °C");
28 }
29
slider_event_cb(lv_event_t * e)30 static void slider_event_cb(lv_event_t * e)
31 {
32 /*Notify all subscribers (only the label now) that the slider value has been changed*/
33 lv_obj_t * slider = lv_event_get_target(e);
34 int32_t v = lv_slider_get_value(slider);
35 lv_msg_send(MSG_NEW_TEMPERATURE, &v);
36 }
37
label_event_cb(lv_event_t * e)38 static void label_event_cb(lv_event_t * e)
39 {
40 lv_obj_t * label = lv_event_get_target(e);
41 lv_msg_t * m = lv_event_get_msg(e);
42
43 const char * fmt = lv_msg_get_user_data(m);
44 const int32_t * v = lv_msg_get_payload(m);
45
46 lv_label_set_text_fmt(label, fmt, *v);
47 }
48
49 #endif
50
