Button matrix (lv_buttonmatrix)

Overview

The Button Matrix object is a lightweight way to display multiple buttons in rows and columns. Lightweight because the buttons are not actually created but just virtually drawn on the fly. This way, one button use only eight extra bytes of memory instead of the ~100-150 bytes a normal Button object plus the 100 or so bytes for the Label object.

The Button matrix is added to the default group (if one is set). Besides the Button matrix is an editable object to allow selecting and clicking the buttons with encoder navigation too.

Parts and Styles

  • LV_PART_MAIN The background of the button matrix, uses the typical background style properties. pad_row and pad_column sets the space between the buttons.

  • LV_PART_ITEMS The buttons all use the text and typical background style properties except translations and transformations.

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_buttonmatrix_set_map(buttonm, my_map). The declaration of a map should look like const char * map[] = {"button1", "button2", "button3", NULL}. Note that the last element has to be either NULL or an empty string ("")!

Use "\n" in the map to insert a line break. E.g. {"button1", "button2", "\n", "button3", ""}. Each line's buttons have their width calculated automatically. So in the example the first row will have 2 buttons each with 50% width and a second row with 1 button having 100% width.

Control buttons

The buttons' width can be set relative to the other button in the same row with lv_buttonmatrix_set_button_width(buttonm, button_id, width) E.g. in a line with two buttons: buttonA, width = 1 and buttonB, width = 2, buttonA will have 33 % width and buttonB will have 66 % width. It's similar to how the "flex-grow" property works in CSS. The width must be in the [1..15] range and the default width is 1.

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

By default, all flags are disabled.

To set or clear a button's control attribute, use lv_buttonmatrix_set_button_ctrl(buttonm, button_id, LV_BUTTONMATRIX_CTRL_...) and lv_buttonmatrix_clear_button_ctrl(buttonm, button_id, LV_BUTTONMATRIX_CTRL_...) respectively. More LV_BUTTONMATRIX_CTRL_... values can be OR-ed

To set/clear the same control attribute for all buttons of a button matrix, use lv_buttonmatrix_set_button_ctrl_all(buttonm, LV_BUTTONMATRIX_CTRL_...) and lv_buttonmatrix_clear_button_ctrl_all(buttonm, LV_BUTTONMATRIX_CTRL_...).

The set a control map for a button matrix (similarly to the map for the text), use lv_buttonmatrix_set_ctrl_map(buttonm, ctrl_map). An element of ctrl_map should look like ctrl_map[0] = width | LV_BUTTONMATRIX_CTRL_NO_REPEAT | LV_BUTTONMATRIX_CTRL_CHECHKABLE. 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_buttonmatrix_set_one_checked(buttonm, true) to allow only one button to be checked at a time.

Events

  • LV_EVENT_VALUE_CHANGED: Sent when a button is pressed/released or repeated after long press. The event parameter is set to the ID of the pressed/released button.

See the events of the Base object too.

lv_buttonmatrix_get_selected_button(buttonm) returns the index of the most recently released or focused button or LV_BUTTONMATRIX_BUTTON_NONE if no such button.

lv_buttonmatrix_get_button_text(buttonm, button_id) returns a pointer to the text of button_idth button.

Learn more about Events.

Keys

  • LV_KEY_RIGHT/UP/LEFT/RIGHT To navigate among the buttons to select one

  • LV_KEY_ENTER To press/release the selected button

Note that long pressing the button matrix with an encoder can mean to enter/leave edit mode and simply long pressing a button to make it repeat as well. To avoid this contradiction it's suggested to add lv_buttonmatrix_set_button_ctrl_all(buttonm, LV_BUTTONMATRIX_CTRL_CLICK_TRIG | LV_BUTTONMATRIX_CTRL_NO_REPEAT) to the button matrix if used with encoder. This way, the pressed button repeat feature is disabled and on leaving edit mode the selected button won't be activated.

Learn more about Keys.

Example

Simple Button matrix

#include "../../lv_examples.h"
#if LV_USE_BUTTONMATRIX && LV_BUILD_EXAMPLES

static void event_handler(lv_event_t * e)
{
    lv_event_code_t code = lv_event_get_code(e);
    lv_obj_t * obj = lv_event_get_target(e);
    if(code == LV_EVENT_VALUE_CHANGED) {
        uint32_t id = lv_buttonmatrix_get_selected_button(obj);
        const char * txt = lv_buttonmatrix_get_button_text(obj, id);
        LV_UNUSED(txt);
        LV_LOG_USER("%s was pressed\n", txt);
    }
}

static const char * btnm_map[] = {"1", "2", "3", "4", "5", "\n",
                                  "6", "7", "8", "9", "0", "\n",
                                  "Action1", "Action2", ""
                                 };

void lv_example_buttonmatrix_1(void)
{
    lv_obj_t * btnm1 = lv_buttonmatrix_create(lv_screen_active());
    lv_buttonmatrix_set_map(btnm1, btnm_map);
    lv_buttonmatrix_set_button_width(btnm1, 10, 2);        /*Make "Action1" twice as wide as "Action2"*/
    lv_buttonmatrix_set_button_ctrl(btnm1, 10, LV_BUTTONMATRIX_CTRL_CHECKABLE);
    lv_buttonmatrix_set_button_ctrl(btnm1, 11, LV_BUTTONMATRIX_CTRL_CHECKED);
    lv_obj_align(btnm1, LV_ALIGN_CENTER, 0, 0);
    lv_obj_add_event_cb(btnm1, event_handler, LV_EVENT_ALL, NULL);
}

#endif

Custom buttons

#include "../../lv_examples.h"
#if LV_USE_BUTTONMATRIX && LV_BUILD_EXAMPLES

static void event_cb(lv_event_t * e)
{
    lv_obj_t * obj = lv_event_get_target(e);
    lv_draw_task_t * draw_task = lv_event_get_draw_task(e);
    lv_draw_dsc_base_t * base_dsc = draw_task->draw_dsc;
    /*When the button matrix draws the buttons...*/
    if(base_dsc->part == LV_PART_ITEMS) {
        bool pressed = false;
        if(lv_buttonmatrix_get_selected_button(obj) == base_dsc->id1 && lv_obj_has_state(obj, LV_STATE_PRESSED)) {
            pressed = true;
        }

        /*Change the draw descriptor of the 2nd button*/
        if(base_dsc->id1 == 1) {
            lv_draw_fill_dsc_t * fill_draw_dsc = lv_draw_task_get_fill_dsc(draw_task);
            if(fill_draw_dsc) {
                fill_draw_dsc->radius = 0;
                if(pressed) fill_draw_dsc->color = lv_palette_darken(LV_PALETTE_BLUE, 3);
                else fill_draw_dsc->color = lv_palette_main(LV_PALETTE_BLUE);
            }
            lv_draw_box_shadow_dsc_t * box_shadow_draw_dsc = lv_draw_task_get_box_shadow_dsc(draw_task);
            if(box_shadow_draw_dsc) {
                box_shadow_draw_dsc->width = 6;
                box_shadow_draw_dsc->ofs_x = 3;
                box_shadow_draw_dsc->ofs_y = 3;
            }
            lv_draw_label_dsc_t * label_draw_dsc = lv_draw_task_get_label_dsc(draw_task);
            if(label_draw_dsc) {
                label_draw_dsc->color = lv_color_white();
            }

        }
        /*Change the draw descriptor of the 3rd button*/
        else if(base_dsc->id1 == 2) {
            lv_draw_fill_dsc_t * fill_draw_dsc = lv_draw_task_get_fill_dsc(draw_task);
            if(fill_draw_dsc) {
                fill_draw_dsc->radius = LV_RADIUS_CIRCLE;
                if(pressed) fill_draw_dsc->color = lv_palette_darken(LV_PALETTE_RED, 3);
                else fill_draw_dsc->color = lv_palette_main(LV_PALETTE_RED);
            }
        }
        else if(base_dsc->id1 == 3) {
            lv_draw_label_dsc_t * label_draw_dsc = lv_draw_task_get_label_dsc(draw_task);
            if(label_draw_dsc) {
                label_draw_dsc->opa = 0;
            }
            if(draw_task->type == LV_DRAW_TASK_TYPE_FILL) {
                LV_IMAGE_DECLARE(img_star);
                lv_image_header_t header;
                lv_result_t res = lv_image_decoder_get_info(&img_star, &header);
                if(res != LV_RESULT_OK) return;

                lv_area_t a;
                a.x1 = 0;
                a.x2 = header.w - 1;
                a.y1 = 0;
                a.y2 = header.h - 1;
                lv_area_align(&draw_task->area, &a, LV_ALIGN_CENTER, 0, 0);

                lv_draw_image_dsc_t img_draw_dsc;
                lv_draw_image_dsc_init(&img_draw_dsc);
                img_draw_dsc.src = &img_star;
                img_draw_dsc.recolor = lv_color_black();
                if(pressed) img_draw_dsc.recolor_opa = LV_OPA_30;

                lv_draw_image(base_dsc->layer, &img_draw_dsc, &a);

            }
        }
    }
}

/**
 * Add custom drawer to the button matrix to customize buttons one by one
 */
void lv_example_buttonmatrix_2(void)
{
    lv_obj_t * btnm = lv_buttonmatrix_create(lv_screen_active());
    lv_obj_add_event_cb(btnm, event_cb, LV_EVENT_DRAW_TASK_ADDED, NULL);
    lv_obj_add_flag(btnm, LV_OBJ_FLAG_SEND_DRAW_TASK_EVENTS);
    lv_obj_center(btnm);
}

#endif

Pagination

#include "../../lv_examples.h"
#if LV_USE_BUTTONMATRIX  && LV_BUILD_EXAMPLES

static void event_cb(lv_event_t * e)
{
    lv_obj_t * obj = lv_event_get_target(e);
    uint32_t id = lv_buttonmatrix_get_selected_button(obj);
    bool prev = id == 0;
    bool next = id == 6;
    if(prev || next) {
        /*Find the checked button*/
        uint32_t i;
        for(i = 1; i < 7; i++) {
            if(lv_buttonmatrix_has_button_ctrl(obj, i, LV_BUTTONMATRIX_CTRL_CHECKED)) break;
        }

        if(prev && i > 1) i--;
        else if(next && i < 5) i++;

        lv_buttonmatrix_set_button_ctrl(obj, i, LV_BUTTONMATRIX_CTRL_CHECKED);
    }
}

/**
 * Make a button group (pagination)
 */
void lv_example_buttonmatrix_3(void)
{
    static lv_style_t style_bg;
    lv_style_init(&style_bg);
    lv_style_set_pad_all(&style_bg, 0);
    lv_style_set_pad_gap(&style_bg, 0);
    lv_style_set_clip_corner(&style_bg, true);
    lv_style_set_radius(&style_bg, LV_RADIUS_CIRCLE);
    lv_style_set_border_width(&style_bg, 0);

    static lv_style_t style_btn;
    lv_style_init(&style_btn);
    lv_style_set_radius(&style_btn, 0);
    lv_style_set_border_width(&style_btn, 1);
    lv_style_set_border_opa(&style_btn, LV_OPA_50);
    lv_style_set_border_color(&style_btn, lv_palette_main(LV_PALETTE_GREY));
    lv_style_set_border_side(&style_btn, LV_BORDER_SIDE_INTERNAL);
    lv_style_set_radius(&style_btn, 0);

    static const char * map[] = {LV_SYMBOL_LEFT, "1", "2", "3", "4", "5", LV_SYMBOL_RIGHT, ""};

    lv_obj_t * btnm = lv_buttonmatrix_create(lv_screen_active());
    lv_buttonmatrix_set_map(btnm, map);
    lv_obj_add_style(btnm, &style_bg, 0);
    lv_obj_add_style(btnm, &style_btn, LV_PART_ITEMS);
    lv_obj_add_event_cb(btnm, event_cb, LV_EVENT_VALUE_CHANGED, NULL);
    lv_obj_set_size(btnm, 225, 35);

    /*Allow selecting on one number at time*/
    lv_buttonmatrix_set_button_ctrl_all(btnm, LV_BUTTONMATRIX_CTRL_CHECKABLE);
    lv_buttonmatrix_clear_button_ctrl(btnm, 0, LV_BUTTONMATRIX_CTRL_CHECKABLE);
    lv_buttonmatrix_clear_button_ctrl(btnm, 6, LV_BUTTONMATRIX_CTRL_CHECKABLE);

    lv_buttonmatrix_set_one_checked(btnm, true);
    lv_buttonmatrix_set_button_ctrl(btnm, 1, LV_BUTTONMATRIX_CTRL_CHECKED);

    lv_obj_center(btnm);

}

#endif

API

lv_buttonmatrix.h

lv_keyboard.h