roller.rst

Roller (lv_roller)

Overview

Roller allows you to simply select one option from a list by scrolling.

Parts and Styles

• :cppLV_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.
• :cppLV_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.

Usage

Set options

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

:cppLV_ROLLER_MODE_INFINITE makes the roller circular.

You can select an option manually with :cpplv_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 :cpplv_roller_get_selected(roller).

:cpplv_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 :cpplv_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.

Events

• :cppLV_EVENT_VALUE_CHANGED Sent when a new option is selected.

See the events of the Base object <lv_obj> too.

Learn more about events.

Keys

• LV_KEY_RIGHT/DOWN Select the next option
• LV_KEY_LEFT/UP Select the previous option
• :cppLY_KEY_ENTER Apply the selected option (Send :cppLV_EVENT_VALUE_CHANGED event)

Example

API