Issue when a button in a row is checked

[tzan]

Important: unclear posts may not receive useful answers.

Before posting

• Get familiar with Markdown to format and structure your post
• Be sure to update lvgl from the latest version from the master branch.
• Be sure you have checked the FAQ and read the relevant part of the documentation.
• If applicable use the Simulator to eliminate hardware related issues.

Delete this section if you read and applied the mentioned points.

Description

Hi all, I would like to create a row of buttons where only one can be checked at the time. A multi-choice control. To do so, I started understanding how to create a row of buttons.

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

simulator

What LVGL version are you using?

8.3.2

What do you want to achieve?

Multi-selection widget where there are for instance 3 or 4 buttons, but only one can be checked.

What have you tried so far?

The example described here:
https://docs.lvgl.io/8.3/layouts/flex.html
“A simple row and a column layout with flexbox”

Code to reproduce

Starting from the example of a simple row with some buttons, I tried to set one of those checked but
once done, it disappeared.
lv_obj_t * cont_row = lv_obj_create(lv_scr_act());
lv_obj_set_size(cont_row, 300, 75);
lv_obj_align(cont_row, LV_ALIGN_TOP_MID, 0, 5);
lv_obj_set_flex_flow(cont_row, LV_FLEX_FLOW_ROW);

uint32_t i;
for(i = 0; i < 10; i++) {
    lv_obj_t * obj;
    lv_obj_t * label;

    /*Add items to the row*/
    obj = lv_btn_create(cont_row);
    lv_obj_set_size(obj, 100, LV_PCT(100));

    label = lv_label_create(obj);
    lv_label_set_text_fmt(label, "Item: %"LV_PRIu32, i);
    lv_obj_center(label);
    if (i == 2) {
        lv_obj_add_flag(obj, LV_STATE_CHECKED);
    }
}

Can you make me understanding why this happen please?

Screenshot and/or video

If possible, add screenshots and/or videos about the current state.