Roller (lv_roller)

Overview

Roller allows you to simply select one option from more with scrolling.

Parts and Styles

The Roller's main part is called LV_ROLLER_PART_BG. It's a rectangle and uses all the typical background properties. The style of the Roller's label is inherited from the text style properties of the background. To adjust the space between the options use the text_line_space style property. The padding style properties set the space on the sides.

The selected option in the middle can be referenced with LV_ROLLER_PART_SELECTED virtual part. Besides the typical background properties it uses the text properties to change the appearance of the text in the selected area.

Usage

Set options

The options are passed to the Roller as a string with lv_roller_set_options(roller, options, LV_ROLLER_MODE_NORMAL/INFINITE). The options should be separated by \n. For example: "First\nSecond\nThird".

LV_ROLLER_MODE_INIFINITE make the roller circular.

You can select an option manually with lv_roller_set_selected(roller, id, LV_ANIM_ON/OFF), where id is the index of an option.

Get selected option

The get the currently selected option use lv_roller_get_selected(roller) it will return the index of the selected option.

lv_roller_get_selected_str(roller, buf, buf_size) copy the name of the selected option to buf.

Align the options

To align the label horizontally use lv_roller_set_align(roller, LV_LABEL_ALIGN_LEFT/CENTER/RIGHT).

Visible rows

The number of visible rows can be adjusted with lv_roller_set_visible_row_count(roller, num)

Animation time

When the Roller is scrolled and doesn't stop exactly on an option it will scroll to the nearest valid option automatically. The time of this scroll animation can be changed by lv_roller_set_anim_time(roller, anim_time). Zero animation time means no animation.

Events

Besides, the Generic events the following Special events are sent by the Drop down lists:

  • LV_EVENT_VALUE_CHANGED sent when a new option is selected

Learn more about Events.

Keys

The following Keys are processed by the Buttons:

  • LV_KEY_RIGHT/DOWN Select the next option

  • LV_KEY_LEFT/UP Select the previous option

  • LY_KEY_ENTER Apply the selected option (Send LV_EVENT_VALUE_CHANGED event)

Example

C

Simple Roller

code

#include "../../../lv_examples.h"
#include <stdio.h>
#if LV_USE_ROLLER

static void event_handler(lv_obj_t * obj, lv_event_t event)
{
    if(event == LV_EVENT_VALUE_CHANGED) {
        char buf[32];
        lv_roller_get_selected_str(obj, buf, sizeof(buf));
        printf("Selected month: %s\n", buf);
    }
}


void lv_ex_roller_1(void)
{
    lv_obj_t *roller1 = lv_roller_create(lv_scr_act(), NULL);
    lv_roller_set_options(roller1,
                        "January\n"
                        "February\n"
                        "March\n"
                        "April\n"
                        "May\n"
                        "June\n"
                        "July\n"
                        "August\n"
                        "September\n"
                        "October\n"
                        "November\n"
                        "December",
                        LV_ROLLER_MODE_INIFINITE);

    lv_roller_set_visible_row_count(roller1, 4);
    lv_obj_align(roller1, NULL, LV_ALIGN_CENTER, 0, 0);
    lv_obj_set_event_cb(roller1, event_handler);
}

#endif

MicroPython

No examples yet.

API

Typedefs

typedef uint8_t lv_roller_mode_t
typedef uint8_t lv_roller_part_t

Enums

enum [anonymous]

Roller mode.

Values:

enumerator LV_ROLLER_MODE_NORMAL

Normal mode (roller ends at the end of the options).

enumerator LV_ROLLER_MODE_INIFINITE

Infinite mode (roller can be scrolled forever).

enum [anonymous]

Values:

enumerator LV_ROLLER_PART_BG = LV_PAGE_PART_BG
enumerator LV_ROLLER_PART_SELECTED = _LV_PAGE_PART_VIRTUAL_LAST
enumerator _LV_ROLLER_PART_VIRTUAL_LAST

Functions

lv_obj_t *lv_roller_create(lv_obj_t *par, const lv_obj_t *copy)

Create a roller object

Return

pointer to the created roller

Parameters
  • par: pointer to an object, it will be the parent of the new roller

  • copy: pointer to a roller object, if not NULL then the new object will be copied from it

void lv_roller_set_options(lv_obj_t *roller, const char *options, lv_roller_mode_t mode)

Set the options on a roller

Parameters
  • roller: pointer to roller object

  • options: a string with '

    ' separated options. E.g. "One\nTwo\nThree"

  • mode: LV_ROLLER_MODE_NORMAL or LV_ROLLER_MODE_INFINITE

void lv_roller_set_align(lv_obj_t *roller, lv_label_align_t align)

Set the align of the roller's options (left, right or center[default])

Parameters
  • roller: - pointer to a roller object

  • align: - one of lv_label_align_t values (left, right, center)

void lv_roller_set_selected(lv_obj_t *roller, uint16_t sel_opt, lv_anim_enable_t anim)

Set the selected option

Parameters
  • roller: pointer to a roller object

  • sel_opt: id of the selected option (0 ... number of option - 1);

  • anim: LV_ANOM_ON: set with animation; LV_ANIM_OFF set immediately

void lv_roller_set_visible_row_count(lv_obj_t *roller, uint8_t row_cnt)

Set the height to show the given number of rows (options)

Parameters
  • roller: pointer to a roller object

  • row_cnt: number of desired visible rows

void lv_roller_set_auto_fit(lv_obj_t *roller, bool auto_fit)

Allow automatically setting the width of roller according to it's content.

Parameters
  • roller: pointer to a roller object

  • auto_fit: true: enable auto fit

void lv_roller_set_anim_time(lv_obj_t *roller, uint16_t anim_time)

Set the open/close animation time.

Parameters
  • roller: pointer to a roller object

  • anim_time: open/close animation time [ms]

uint16_t lv_roller_get_selected(const lv_obj_t *roller)

Get the id of the selected option

Return

id of the selected option (0 ... number of option - 1);

Parameters
  • roller: pointer to a roller object

uint16_t lv_roller_get_option_cnt(const lv_obj_t *roller)

Get the total number of options

Return

the total number of options in the list

Parameters
  • roller: pointer to a roller object

void lv_roller_get_selected_str(const lv_obj_t *roller, char *buf, uint32_t buf_size)

Get the current selected option as a string

Parameters
  • roller: pointer to roller object

  • buf: pointer to an array to store the string

  • buf_size: size of buf in bytes. 0: to ignore it.

lv_label_align_t lv_roller_get_align(const lv_obj_t *roller)

Get the align attribute. Default alignment after _create is LV_LABEL_ALIGN_CENTER

Return

LV_LABEL_ALIGN_LEFT, LV_LABEL_ALIGN_RIGHT or LV_LABEL_ALIGN_CENTER

Parameters
  • roller: pointer to a roller object

bool lv_roller_get_auto_fit(lv_obj_t *roller)

Get whether the auto fit option is enabled or not.

Return

true: auto fit is enabled

Parameters
  • roller: pointer to a roller object

const char *lv_roller_get_options(const lv_obj_t *roller)

Get the options of a roller

Return

the options separated by '

'-s (E.g. "Option1\nOption2\nOption3")

Parameters
  • roller: pointer to roller object

uint16_t lv_roller_get_anim_time(const lv_obj_t *roller)

Get the open/close animation time.

Return

open/close animation time [ms]

Parameters
  • roller: pointer to a roller

struct lv_roller_ext_t

Public Members

lv_page_ext_t page
lv_style_list_t style_sel
uint16_t option_cnt
uint16_t sel_opt_id
uint16_t sel_opt_id_ori
lv_roller_mode_t mode
uint8_t auto_fit