LuatOS/module/Air8101/demo/lvgl/lvgl_demo_test/dropdown_demo.lua

local dropdown_demo = {}

--demo1
local function event_handler(obj, event)
    if(event == lvgl.EVENT_VALUE_CHANGED) then
        local buf = lvgl.dropdown_get_selected_str(obj, 20);
        print(string.format("Option: %s\n", buf))
    end
end

function dropdown_demo.demo1()
    --Create a normal drop down list
    local ddlist = lvgl.dropdown_create(lvgl.scr_act(), nil);
    lvgl.dropdown_set_options(ddlist, 
[[Apple
Banana
Orange
Melon
Grape
Raspberry]]);

    lvgl.obj_align(ddlist, nil, lvgl.ALIGN_IN_TOP_MID, 0, 20);
    lvgl.obj_set_event_cb(ddlist, event_handler);
end

--demo2
function dropdown_demo.demo2()
    --Create a normal drop down list
    local ddlist = lvgl.dropdown_create(lvgl.scr_act(), nil);
    lvgl.dropdown_set_options(ddlist, 
[[Apple
Banana
Orange
Melon
Grape
Raspberry]]);

    lvgl.dropdown_set_dir(ddlist, lvgl.DROPDOWN_DIR_LEFT);
    lvgl.dropdown_set_symbol(ddlist, nil);
    lvgl.dropdown_set_show_selected(ddlist, false);
    lvgl.dropdown_set_text(ddlist, "Fruits");

    --It will be called automatically when the size changes
    lvgl.obj_align(ddlist, nil, lvgl.ALIGN_IN_TOP_RIGHT, 0, 20);

    --Copy the drop LEFT list
    ddlist = lvgl.dropdown_create(lvgl.scr_act(), ddlist);
    lvgl.obj_align(ddlist, nil, lvgl.ALIGN_IN_TOP_RIGHT, 0, 100);
end

return dropdown_demo