Help in getting a button click to increment a roller

How-to
1

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Description

Need help with Button click to increment Roller

What MCU/Processor/Board and compiler are you using?

Win32 Simulator

What do you want to achieve?

I want to be able to click on a button which then increments a roller widget.

What have you tried so far?

Code to reproduce

Add the relevant code snippets here.

The code block(s) should be between ```c and ``` tags:

static void event_handlerHour(lv_event_t* e2)
{
    lv_event_code_t code = lv_event_get_code(e2);
    lv_obj_t* obj2 = (lv_obj_t*)lv_event_get_target(e2);
    if (code == LV_EVENT_VALUE_CHANGED) {
        char buf[32];
        lv_roller_get_selected_str(obj2, buf, sizeof(buf));
        LV_LOG_USER("Selected hour: %s\n", buf);
    }
}

/**
 * An infinite roller with the name of the months
 */
void lv_hour_roller(void)
{
    lv_obj_t* roller1 = lv_roller_create(lv_scr_act());
    lv_roller_set_options(roller1,
        "01\n""02\n""03\n""04\n""05\n""06\n""07\n""08\n""09\n""10\n""11\n""12",
        LV_ROLLER_MODE_INFINITE);

    lv_roller_set_visible_row_count(roller1, 5);
    lv_obj_align(roller1, LV_ALIGN_CENTER, 0, 0);
    lv_obj_add_event(roller1, event_handlerHour, LV_EVENT_KEY, NULL);
}

static void event_handler(lv_event_t* e)
{
    lv_event_code_t code = lv_event_get_code(e);

    if (code == LV_EVENT_CLICKED) {
        LV_LOG_USER("Clicked");
        lv_obj_send_event(obj2, LV_EVENT_CLICKED, NULL); // ERROR HERE, OBJ2 not defined
    }
    else if (code == LV_EVENT_VALUE_CHANGED) {
        LV_LOG_USER("Toggled");
    }
}

void lv_button(void)
{
    lv_obj_t* label;
   
    lv_obj_t* btn1 = lv_btn_create(lv_scr_act());
    lv_obj_align(btn1, LV_ALIGN_BOTTOM_MID, 0, -25);
    lv_obj_add_event(btn1, event_handler, LV_EVENT_CLICKED, NULL);    
    label = lv_label_create(btn1);
    lv_label_set_text(label, "Up");
    lv_obj_center(label);
}

There error is in the event_handler(). OBJ2 is not defined. What is supposed to go here?
I guess I don’t understand how the “lv_obj_send_event()” function is supposed to work. Is there another way to send a button click to the roller? If there is, can some kind soul point me to the part in the docs that explains it? Or maybe an example?

Thanks,
Richard.

2

You can do this in the button’s click event:

lv_roller_set_selected(roller, lv_roller_get_selected(roller) + 1, LV_ANIM_ON);
3

Thank you so much for pointing me in the proper direction.

I do have one issue. I am getting an error when I use your suggested line of code " ```
lv_roller_set_selected(roller, lv_roller_get_selected(roller) + 1, LV_ANIM_ON);

The error message says:
lv_roller_get_selected: Asserted at expression: obj != NULL (The object is NULL)

When I try "uint16_t current_hour = lv_roller_get_selected(roller1);" I get the same error.

I don't know if this makes a difference or not but I'm using the Win32 simulator.
Any ideas what is wrong?  Thanks again,

Richard
4

This works for me in lvgl v9

lv_obj_t* roller;

static void event_handlerHour(lv_event_t* e2)
{
    lv_event_code_t code = lv_event_get_code(e2);
    lv_obj_t* obj2 = (lv_obj_t*)lv_event_get_target(e2);
    if (code == LV_EVENT_VALUE_CHANGED) {
        char buf[32];
        lv_roller_get_selected_str(obj2, buf, sizeof(buf));
        LV_LOG_USER("Selected hour: %s\n", buf);
    }
}

static void button_event_handler(lv_event_t* e)
{
    lv_event_code_t code = lv_event_get_code(e);

    if (code == LV_EVENT_CLICKED) {
        LV_LOG_USER("Clicked");
        lv_roller_set_selected(roller, lv_roller_get_selected(roller) + 1, LV_ANIM_ON);
    }
    else if (code == LV_EVENT_VALUE_CHANGED) {
        LV_LOG_USER("Toggled");
    }
}

int main () {

   /* Setup */

  roller = lv_roller_create(lv_scr_act());
  lv_roller_set_options(roller,
      "01\n""02\n""03\n""04\n""05\n""06\n""07\n""08\n""09\n""10\n""11\n""12",
      LV_ROLLER_MODE_INFINITE);

  lv_roller_set_visible_row_count(roller, 5);
  lv_obj_align(roller, LV_ALIGN_CENTER, 0, 0);
  lv_obj_add_event(roller, event_handlerHour, LV_EVENT_KEY, NULL);

  lv_obj_t* label;

  lv_obj_t* btn1 = lv_btn_create(lv_scr_act());
  lv_obj_align(btn1, LV_ALIGN_BOTTOM_MID, 0, -25);
  lv_obj_add_event(btn1, button_event_handler, LV_EVENT_CLICKED, NULL);
  label = lv_label_create(btn1);
  lv_label_set_text(label, "Up");
  lv_obj_center(label);

  /* Infinite loop */



}
1 Like
5

Thanks Carlos. You saved me a ton frustration.