lvgl/docs/widgets/btnmatrix.md

.. include:: /header.rst 
:github_url: |github_link_base|/widgets/btnmatrix.md

Button matrix (lv_btnmatrix)

Overview

The Button Matrix objects can display multiple buttons in rows and columns.

The main reasons for wanting to use a button matrix instead of a container and individual button objects are:

• The button matrix is simpler to use for grid-based button layouts.
• The button matrix consumes a lot less memory per button.

Parts and Styles

The Button matrix's main part is called LV_BTNMATRIX_PART_BG. It draws a background using the typical background style properties.

LV_BTNMATRIX_PART_BTN is virtual part and it refers to the buttons on the button matrix. It also uses all the typical background properties.

The top/bottom/left/right padding values from the background are used to keep some space on the sides. Inner padding is applied between the buttons.

Usage

Button's text

There is a text on each button. To specify them a descriptor string array, called map, needs to be used. The map can be set with lv_btnmatrix_set_map(btnm, my_map). The declaration of a map should look like const char * map[] = {"btn1", "btn2", "btn3", ""}. Note that the last element has to be an empty string!

Use "\n" in the map to make line break. E.g. {"btn1", "btn2", "\n", "btn3", ""}. Each line's buttons have their width calculated automatically.

Control buttons

The buttons width can be set relative to the other button in the same line with lv_btnmatrix_set_btn_width(btnm, btn_id, width) E.g. in a line with two buttons: btnA, width = 1 and btnB, width = 2, btnA will have 33 % width and btnB will have 66 % width. It's similar to how the flex-grow property works in CSS.

In addition to width, each button can be customized with the following parameters:

• LV_BTNMATRIX_CTRL_HIDDEN - make a button hidden (hidden buttons still take up space in the layout, they are just not visible or clickable)
• LV_BTNMATRIX_CTRL_NO_REPEAT - disable repeating when the button is long pressed
• LV_BTNMATRIX_CTRL_DISABLED - make a button disabled
• LV_BTNMATRIX_CTRL_CHECKABLE - enable toggling of a button
• LV_BTNMATRIX_CTRL_CHECK_STATE - set the toggle state
• LV_BTNMATRIX_CTRL_CLICK_TRIG - if 0, the button will react on press, if 1, will react on release

The set or clear a button's control attribute, use lv_btnmatrix_set_btn_ctrl(btnm, btn_id, LV_BTNM_CTRL_...) and lv_btnmatrix_clear_btn_ctrl(btnm, btn_id, LV_BTNM_CTRL_...) respectively. More LV_BTNM_CTRL_... values can be Ored

The set/clear the same control attribute for all buttons of a button matrix, use lv_btnmatrix_set_btn_ctrl_all(btnm, btn_id, LV_BTNM_CTRL_...) and lv_btnmatrix_clear_btn_ctrl_all(btnm, btn_id, LV_BTNM_CTRL_...).

The set a control map for a button matrix (similarly to the map for the text), use lv_btnmatrix_set_ctrl_map(btnm, ctrl_map). An element of ctrl_map should look like ctrl_map[0] = width | LV_BTNM_CTRL_NO_REPEAT | LV_BTNM_CTRL_TGL_ENABLE. The number of elements should be equal to the number of buttons (excluding newlines characters).

One check

The "One check" feature can be enabled with lv_btnmatrix_set_one_check(btnm, true) to allow only one button to be checked (toggled) at once.

Recolor

The texts on the button can be recolored similarly to the recolor feature for Label object. To enable it, use lv_btnmatrix_set_recolor(btnm, true). After that a button with #FF0000 Red# text will be red.

Aligning the button's text

To align the text on the buttons, use lv_btnmatrix_set_align(roller, LV_LABEL_ALIGN_LEFT/CENTER/RIGHT). All text items in the button matrix will conform to the alignment proprty as it is set.

Notes

The Button matrix object is very light weighted because the buttons are not created just virtually drawn on the fly. This way, 1 button use only 8 extra bytes instead of the ~100-150 byte size of a normal Button object (plus the size of its container and a label for each button).

The disadvantage of this setup is that the ability to style individual buttons to be different from others is limited (aside from the toggling feature). If you require that ability, using individual buttons is very likely to be a better approach.

Events

Besides the Generic events, the following Special events are sent by the button matrices:

• LV_EVENT_VALUE_CHANGED - sent when the button is pressed/released or repeated after long press. The event data is set to the ID of the pressed/released button.

Learn more about Events.

Keys

The following Keys are processed by the Buttons:

• LV_KEY_RIGHT/UP/LEFT/RIGHT - To navigate among the buttons to select one
• LV_KEY_ENTER - To press/release the selected button

Learn more about Keys.

Example

.. include:: /lv_examples/src/lv_ex_widgets/lv_ex_btnmatrix/index.rst

API

.. doxygenfile:: lv_btnmatrix.h
  :project: lvgl