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.. _lv_roller:
==================
Roller (lv_roller)
==================
Overview
********
Roller allows you to simply select one option from a list by scrolling.
.. _lv_roller_parts_and_styles:
Parts and Styles
****************
- :cpp:enumerator:`LV_PART_MAIN` The background of the roller uses all the typical
background properties and text style properties.
``style_text_line_space`` adjusts the space between the options. When
the Roller is scrolled and doesn't stop exactly on an option it will
scroll to the nearest valid option automatically in ``anim_time``
milliseconds as specified in the style.
- :cpp:enumerator:`LV_PART_SELECTED` The selected option in the middle. Besides the
typical background properties it uses the text style properties to
change the appearance of the text in the selected area.
.. _lv_roller_usage:
Usage
*****
Set options
-----------
Options are passed to the Roller as a string with
:cpp:expr:`lv_roller_set_options(roller, options, LV_ROLLER_MODE_NORMAL)`.
The options should be separated by ``\n``. For example:
``"First\nSecond\nThird"``.
:cpp:enumerator:`LV_ROLLER_MODE_INFINITE` makes the roller circular.
You can select an option manually with
:cpp:expr:`lv_roller_set_selected(roller, id, LV_ANIM_ON)`,
where *id* is the index of an option.
Get selected option
-------------------
To get the *index* of the currently selected option use :cpp:expr:`lv_roller_get_selected(roller)`.
:cpp:expr:`lv_roller_get_selected_str(roller, buf, buf_size)` will copy the name of the selected option to ``buf``.
Visible rows
------------
The number of visible rows can be adjusted with :cpp:expr:`lv_roller_set_visible_row_count(roller, num)`.
This function calculates the height with the current style. If the font,
line space, border width, etc. of the roller changes this function needs
to be called again.
.. _lv_roller_events:
Events
******
- :cpp:enumerator:`LV_EVENT_VALUE_CHANGED` Sent when a new option is selected.
See the events of the :ref:`Base object <lv_obj>` too.
Learn more about :ref:`events`.
.. _lv_roller_keys:
Keys
****
- ``LV_KEY_RIGHT/DOWN`` Select the next option
- ``LV_KEY_LEFT/UP`` Select the previous option
- :cpp:enumerator:`LY_KEY_ENTER` Apply the selected option (Send :cpp:enumerator:`LV_EVENT_VALUE_CHANGED` event)
.. _lv_roller_example:
Example
*******
.. include:: ../examples/widgets/roller/index.rst
.. _lv_roller_api:
API
***
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