1# Drop-down list (lv_dropdown)
2
3
4## Overview
5
6The drop-down list allows the user to select one value from a list.
7
8The drop-down list is closed by default and displays a single value or a predefined text.
9When activated (by click on the drop-down list), a list is created from which the user may select one option.
10When the user selects a new value, the list is deleted again.
11
12The Drop-down list is added to the default group (if it is set). Besides the Drop-down list is an editable object to allow selecting an option with encoder navigation too.
13
14## Parts and Styles
15The Dropdown widget is built from the elements: "button" and "list" (both not related to the button and list widgets)
16
17### Button
18- `LV_PART_MAIN` The background of the button. Uses the typical background properties and text properties for the text on it.
19- `LV_PART_INDICATOR` Typically an arrow symbol that can be an image or a text (`LV_SYMBOL`).
20
21The button goes to `LV_STATE_CHECKED` when it's opened.
22
23### List
24- `LV_PART_MAIN` The list itself. Uses the typical background properties. `max_height` can be used to limit the height of the list.
25- `LV_PART_SCROLLBAR` The scrollbar background, border, shadow properties and width (for its own width) and right padding for the spacing on the right.
26- `LV_PART_SELECTED` Refers to the currently pressed, checked or pressed+checked option. Also uses the typical background properties.
27
28The list is hidden/shown on open/close. To add styles to it use `lv_dropdown_get_list(dropdown)`  to get the list object. For example:
29
30```c
31lv_obj_t * list = lv_dropdown_get_list(dropdown) /*Get the list*/
32lv_obj_add_style(list, &my_style, ...)           /*Add the styles to the list*/}`
33```
34
35Alternatively the theme can be extended with the new styles.
36
37## Usage
38
39## Overview
40
41### Set options
42Options are passed to the drop-down list as a string with `lv_dropdown_set_options(dropdown, options)`. Options should be separated by `\n`. For example: `"First\nSecond\nThird"`. This string will be saved in the drop-down list, so it can in a local variable.
43
44The `lv_dropdown_add_option(dropdown, "New option", pos)` function inserts a new option to `pos` index.
45
46To save memory the options can set from a static(constant) string too with `lv_dropdown_set_static_options(dropdown, options)`.
47In this case the options string should be alive while the drop-down list exists and `lv_dropdown_add_option` can't be used
48
49You can select an option manually with `lv_dropdown_set_selected(dropdown, id)`, where `id` is the index of an option.
50
51### Get selected option
52The get the *index* of the selected option, use `lv_dropdown_get_selected(dropdown)`.
53
54`lv_dropdown_get_selected_str(dropdown, buf, buf_size)` copies the *name* of the selected option to `buf`.
55
56### Direction
57The list can be created on any side. The default `LV_DIR_BOTTOM` can be modified by `lv_dropdown_set_dir(dropdown, LV_DIR_LEFT/RIGHT/UP/BOTTOM)` function.
58
59If the list would be vertically out of the screen, it will be aligned to the edge.
60
61### Symbol
62A symbol (typically an arrow) can be added to the dropdown list with `lv_dropdown_set_symbol(dropdown, LV_SYMBOL_...)`
63
64If the direction of the drop-down list is  `LV_DIR_LEFT` the symbol will be shown on the left, otherwise on the right.
65
66### Show selected
67The main part can either show the selected option or a static text. If a static is set with `lv_dropdown_set_text(dropdown, "Some text")` it will be shown regardless to th selected option.
68If the text is `NULL` the selected option is displayed on the button.
69
70### Manually open/close
71To manually open or close the drop-down list the `lv_dropdown_open/close(dropdown)` function can be used.
72
73## Events
74Apart from the [Generic events](../overview/event.html#generic-events), the following [Special events](../overview/event.html#special-events) are sent by the drop-down list:
75- `LV_EVENT_VALUE_CHANGED` Sent when the new option is selected or the list is opened/closed.
76- `LV_EVENT_CANCEL`  Sent when the list is closed
77- `LV_EVENT_READY` Sent when the list is opened
78
79See the events of the [Base object](/widgets/obj) too.
80
81Learn more about [Events](/overview/event).
82
83## Keys
84- `LV_KEY_RIGHT/DOWN` Select the next option.
85- `LV_KEY_LEFT/UP` Select the previous option.
86- `LY_KEY_ENTER` Apply the selected option (Sends `LV_EVENT_VALUE_CHANGED` event and closes the drop-down list).
87
88Learn more about [Keys](/overview/indev).
89
90## Example
91
92```eval_rst
93
94.. include:: ../../../examples/widgets/dropdown/index.rst
95
96```
97
98## API
99
100```eval_rst
101
102.. doxygenfile:: lv_dropdown.h
103  :project: lvgl
104
105```
106