Drop down list - rockcastle/lvgl GitHub Wiki

Written for v5.1

Overview

Drop Down Lists allow you to simply select one option from more. The Drop Down List is closed by default an show the currently selected text. If you click on it the this list opens and all the options are shown.

The options are passed to the Drop Down List as a string with lv_ddlist_set_options(ddlist, options). The options should be separated by \n. For example: "First\nSecond\nThird".

You can select an option manually with lv_ddlist_set_selected(ddlist, id), where id is the index of an option.

A callback function can be specified with lv_ddlist_set_action(ddlist, my_action) to call when a new option is selected.

By default the list's height is adjusted automatically to show all options. The lv_ddlist_set_fix_height(ddlist, h) sets a fixed height for the opened list.

The width is also adjusted automatically. To prevent this apply lv_ddlist_set_hor_fit(ddlist, false) and set the width manually by lv_obj_set_width(ddlist, width).

Similarly to Page with fix height the Drop Down List supports various scrollbar display modes. It can be set by lv_ddlist_set_sb_mode(ddlist, LV_SB_MODE_...).

The Drop Down List open/close animation time is adjusted by lv_ddlist_set_anim_time(ddlist, anim_time). Zero animation time means no animation.

Style usage

The lv_ddlist_set_style(ddlist, LV_DDLIST_STYLE_..., &style) set the styles of a Drop Down List.

• LV_DDLIST_STYLE_BG Style of the background. All style.body properties are used. It is used for the label's style from style.text. Default: lv_style_pretty
• LV_DDLIST_STYLE_SEL Style of the selected option. The style.body properties are used. The selected option will be recolored with text.color. Default: lv_style_plain_color
• LV_DDLIST_STYLE_SB Style of the scrollbar. The style.body properties are used. Default: lv_style_plain_color

Example

static lv_res_t ddlist_action(lv_obj_t * ddlist)
{
    uint8_t id = lv_obj_get_free_num(ddlist);

    char sel_str[32];
    lv_ddlist_get_selected_str(ddlist, sel_str);
    printf("Ddlist %d new option: %s \n", id, sel_str);

    return LV_RES_OK; /*Return OK if the drop down list is not deleted*/
}


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/*Create a drop down list*/
lv_obj_t * ddl1 = lv_ddlist_create(lv_scr_act(), NULL);
lv_ddlist_set_options(ddl1, "Apple\n"
                            "Banana\n"
                            "Orange\n"
                            "Melon\n"
                            "Grape\n"
                            "Raspberry");
lv_obj_align(ddl1, NULL, LV_ALIGN_IN_TOP_LEFT, 30, 10);
lv_obj_set_free_num(ddl1, 1);               /*Set a unique ID*/
lv_ddlist_set_action(ddl1, ddlist_action);  /*Set a function to call when anew option is chosen*/

/*Create a style*/
static lv_style_t style_bg;
lv_style_copy(&style_bg, &lv_style_pretty);
style_bg.body.shadow.width = 4; /*Enable the shadow*/
style_bg.text.color = LV_COLOR_MAKE(0x10, 0x20, 0x50);

/*Copy the drop down list and set the new style_bg*/
lv_obj_t * ddl2 = lv_ddlist_create(lv_scr_act(), ddl1);
lv_obj_align(ddl2, NULL, LV_ALIGN_IN_TOP_RIGHT, -30, 10);
lv_obj_set_free_num(ddl2, 2);       /*Set a unique ID*/
lv_obj_set_style(ddl2, &style_bg);