Grid navigation

Grid navigation (gridnav for short) is a feature that changes the currently focused child object as arrow keys are pressed.

If the children are arranged into a grid-like layout then the up, down, left and right arrows move focus to the nearest sibling in the respective direction.

It doesn't matter how the children are positioned, as only the current x and y coordinates are considered. This means that gridnav works with manually positioned children, as well as Flex and Grid layouts.

Gridnav also works if the children are arranged into a single row or column. That makes it useful, for example, to simplify navigation on a List widget.

Gridnav assumes that the object to which gridnav is added is part of a group. This way, if the object with gridnav is focused, the arrow key presses are automatically forwarded to the object so that gridnav can process the arrow keys.

To move the focus to the next widget of the group use LV_KEY_NEXT or LV_KEY_PREV. Optionally you can also use lv_group_focus_next() or lv_group_focus_prev() or the TAB key on keyboard as usual.

If the container is scrollable and the focused child is out of the view, gridnav will automatically scroll the child into view.

Usage

To add the gridnav feature to an object use lv_gridnav_add(cont, flags).

flags control the behavior of gridnav:

• LV_GRIDNAV_CTRL_NONE: Default settings

• LV_GRIDNAV_CTRL_ROLLOVER: If there is no next/previous object in a direction, the focus goes to the object in the next/previous row (on left/right keys) or first/last row (on up/down keys)

• LV_GRIDNAV_CTRL_SCROLL_FIRST: If an arrow is pressed and the focused object can be scrolled in that direction then it will be scrolled instead of going to the next/previous object. If there is no more room for scrolling the next/previous object will be focused normally

lv_gridnav_remove(cont) Removes gridnav from an object.

Focusable objects

An object needs to be clickable or click focusable (LV_OBJ_FLAG_CLICKABLE or LV_OBJ_FLAG_CLICK_FOCUSABLE) and not hidden (LV_OBJ_FLAG_HIDDEN) to be focusable by gridnav.

Example

Basic grid navigation

C code  

 View on GitHub

#include "../../lv_examples.h"
#if LV_USE_GRIDNAV && LV_USE_FLEX && LV_BUILD_EXAMPLES

/**
 * Demonstrate a a basic grid navigation
 */
void lv_example_gridnav_1(void)
{
    /*It's assumed that the default group is set and
     *there is a keyboard indev*/

    lv_obj_t * cont1 = lv_obj_create(lv_screen_active());
    lv_gridnav_add(cont1, LV_GRIDNAV_CTRL_NONE);

    /*Use flex here, but works with grid or manually placed objects as well*/
    lv_obj_set_flex_flow(cont1, LV_FLEX_FLOW_ROW_WRAP);
    lv_obj_set_style_bg_color(cont1, lv_palette_lighten(LV_PALETTE_BLUE, 5), LV_STATE_FOCUSED);
    lv_obj_set_size(cont1, lv_pct(50), lv_pct(100));

    /*Only the container needs to be in a group*/
    lv_group_add_obj(lv_group_get_default(), cont1);

    lv_obj_t * label = lv_label_create(cont1);
    lv_label_set_text_fmt(label, "No rollover");

    uint32_t i;
    for(i = 0; i < 10; i++) {
        lv_obj_t * obj = lv_button_create(cont1);
        lv_obj_set_size(obj, 70, LV_SIZE_CONTENT);
        lv_obj_add_flag(obj, LV_OBJ_FLAG_CHECKABLE);
        lv_group_remove_obj(obj);   /*Not needed, we use the gridnav instead*/

        label = lv_label_create(obj);
        lv_label_set_text_fmt(label, "%"LV_PRIu32"", i);
        lv_obj_center(label);
    }

    /* Create a second container with rollover grid nav mode.*/

    lv_obj_t * cont2 = lv_obj_create(lv_screen_active());
    lv_gridnav_add(cont2, LV_GRIDNAV_CTRL_ROLLOVER);
    lv_obj_set_style_bg_color(cont2, lv_palette_lighten(LV_PALETTE_BLUE, 5), LV_STATE_FOCUSED);
    lv_obj_set_size(cont2, lv_pct(50), lv_pct(100));
    lv_obj_align(cont2, LV_ALIGN_RIGHT_MID, 0, 0);

    label = lv_label_create(cont2);
    lv_obj_set_width(label, lv_pct(100));
    lv_label_set_text_fmt(label, "Rollover\nUse tab to focus the other container");

    /*Only the container needs to be in a group*/
    lv_group_add_obj(lv_group_get_default(), cont2);

    /*Add and place some children manually*/
    lv_obj_t * ta = lv_textarea_create(cont2);
    lv_obj_set_size(ta, lv_pct(100), 80);
    lv_obj_set_pos(ta, 0, 80);
    lv_group_remove_obj(ta);   /*Not needed, we use the gridnav instead*/

    lv_obj_t * cb = lv_checkbox_create(cont2);
    lv_obj_set_pos(cb, 0, 170);
    lv_group_remove_obj(cb);   /*Not needed, we use the gridnav instead*/

    lv_obj_t * sw1 = lv_switch_create(cont2);
    lv_obj_set_pos(sw1, 0, 200);
    lv_group_remove_obj(sw1);   /*Not needed, we use the gridnav instead*/

    lv_obj_t * sw2 = lv_switch_create(cont2);
    lv_obj_set_pos(sw2, lv_pct(50), 200);
    lv_group_remove_obj(sw2);   /*Not needed, we use the gridnav instead*/
}

#endif

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Grid navigation on a list

C code  

 View on GitHub

#include "../../lv_examples.h"
#if LV_USE_GRIDNAV && LV_USE_LIST && LV_BUILD_EXAMPLES

/**
 * Grid navigation on a list
 */
void lv_example_gridnav_2(void)
{
    /*It's assumed that the default group is set and
     *there is a keyboard indev*/

    lv_obj_t * list1 = lv_list_create(lv_screen_active());
    lv_gridnav_add(list1, LV_GRIDNAV_CTRL_NONE);
    lv_obj_set_size(list1, lv_pct(45), lv_pct(80));
    lv_obj_align(list1, LV_ALIGN_LEFT_MID, 5, 0);
    lv_obj_set_style_bg_color(list1, lv_palette_lighten(LV_PALETTE_BLUE, 5), LV_STATE_FOCUSED);
    lv_group_add_obj(lv_group_get_default(), list1);

    char buf[32];
    uint32_t i;
    for(i = 0; i < 15; i++) {
        lv_snprintf(buf, sizeof(buf), "File %d", i + 1);
        lv_obj_t * item = lv_list_add_button(list1, LV_SYMBOL_FILE, buf);
        lv_obj_set_style_bg_opa(item, 0, 0);
        lv_group_remove_obj(item);   /*Not needed, we use the gridnav instead*/
    }

    lv_obj_t * list2 = lv_list_create(lv_screen_active());
    lv_gridnav_add(list2, LV_GRIDNAV_CTRL_ROLLOVER);
    lv_obj_set_size(list2, lv_pct(45), lv_pct(80));
    lv_obj_align(list2, LV_ALIGN_RIGHT_MID, -5, 0);
    lv_obj_set_style_bg_color(list2, lv_palette_lighten(LV_PALETTE_BLUE, 5), LV_STATE_FOCUSED);
    lv_group_add_obj(lv_group_get_default(), list2);

    for(i = 0; i < 15; i++) {
        lv_snprintf(buf, sizeof(buf), "Folder %d", i + 1);
        lv_obj_t * item = lv_list_add_button(list2, LV_SYMBOL_DIRECTORY, buf);
        lv_obj_set_style_bg_opa(item, 0, 0);
        lv_group_remove_obj(item);
    }
}

#endif

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Nested grid navigations

C code  

 View on GitHub

#include "../../lv_examples.h"
#if LV_USE_GRIDNAV && LV_USE_FLEX && LV_BUILD_EXAMPLES

static void cont_sub_event_cb(lv_event_t * e)
{
    uint32_t k = lv_event_get_key(e);
    lv_obj_t * obj = lv_event_get_target(e);
    if(k == LV_KEY_ENTER) {
        lv_group_focus_obj(obj);
    }
    else if(k == LV_KEY_ESC) {
        lv_group_focus_next(lv_obj_get_group(obj));
    }

}

/**
 * Nested grid navigations
 */
void lv_example_gridnav_3(void)
{
    /*It's assumed that the default group is set and
     *there is a keyboard indev*/

    lv_obj_t * cont_main = lv_obj_create(lv_screen_active());
    lv_gridnav_add(cont_main, LV_GRIDNAV_CTRL_ROLLOVER | LV_GRIDNAV_CTRL_SCROLL_FIRST);

    /*Only the container needs to be in a group*/
    lv_group_add_obj(lv_group_get_default(), cont_main);

    /*Use flex here, but works with grid or manually placed objects as well*/
    lv_obj_set_flex_flow(cont_main, LV_FLEX_FLOW_ROW_WRAP);
    lv_obj_set_style_bg_color(cont_main, lv_palette_lighten(LV_PALETTE_BLUE, 5), LV_STATE_FOCUSED);
    lv_obj_set_size(cont_main, lv_pct(80), LV_SIZE_CONTENT);

    lv_obj_t * btn;
    lv_obj_t * label;

    btn = lv_button_create(cont_main);
    lv_group_remove_obj(btn);
    label = lv_label_create(btn);
    lv_label_set_text(label, "Button 1");

    btn = lv_button_create(cont_main);
    lv_group_remove_obj(btn);
    label = lv_label_create(btn);
    lv_label_set_text(label, "Button 2");

    /*Create an other container with long text to show how LV_GRIDNAV_CTRL_SCROLL_FIRST works*/
    lv_obj_t * cont_sub1 = lv_obj_create(cont_main);
    lv_obj_set_size(cont_sub1, lv_pct(100), 100);

    label = lv_label_create(cont_sub1);
    lv_obj_set_style_bg_color(cont_sub1, lv_palette_lighten(LV_PALETTE_RED, 5), LV_STATE_FOCUSED);
    lv_obj_set_width(label, lv_pct(100));
    lv_label_set_text(label,
                      "I'm a very long text which is makes my container scrollable. "
                      "As LV_GRIDNAV_FLAG_SCROLL_FIRST is enabled arrow will scroll me first "
                      "and a new objects will be focused only when an edge is reached with the scrolling.\n\n"
                      "This is only some placeholder text to be sure the parent will be scrollable. \n\n"
                      "Hello world!\n"
                      "Hello world!\n"
                      "Hello world!\n"
                      "Hello world!\n"
                      "Hello world!\n"
                      "Hello world!");

    /*Create a third container that can be focused with ENTER and contains an other grid nav*/
    lv_obj_t * cont_sub2 = lv_obj_create(cont_main);
    lv_gridnav_add(cont_sub2, LV_GRIDNAV_CTRL_ROLLOVER);
    /*Only the container needs to be in a group*/
    lv_group_add_obj(lv_group_get_default(), cont_sub2);

    lv_obj_add_event_cb(cont_sub2, cont_sub_event_cb, LV_EVENT_KEY, NULL);

    /*Use flex here, but works with grid or manually placed objects as well*/
    lv_obj_set_flex_flow(cont_sub2, LV_FLEX_FLOW_ROW_WRAP);
    lv_obj_set_style_bg_color(cont_sub2, lv_palette_lighten(LV_PALETTE_RED, 5), LV_STATE_FOCUSED);
    lv_obj_set_size(cont_sub2, lv_pct(100), LV_SIZE_CONTENT);

    label = lv_label_create(cont_sub2);
    lv_label_set_text(label, "Use ENTER/ESC to focus/defocus this container");
    lv_obj_set_width(label, lv_pct(100));

    btn = lv_button_create(cont_sub2);
    lv_group_remove_obj(btn);
    label = lv_label_create(btn);
    lv_label_set_text(label, "Button 3");

    btn = lv_button_create(cont_sub2);
    lv_group_remove_obj(btn);
    label = lv_label_create(btn);
    lv_label_set_text(label, "Button 4");

}

#endif

---

Simple navigation on a list widget

C code  

 View on GitHub

#include "../../lv_examples.h"
#if LV_USE_GRIDNAV && LV_USE_FLEX && LV_BUILD_EXAMPLES

static void event_handler(lv_event_t * e)
{
    lv_obj_t * obj = lv_event_get_target(e);
    lv_obj_t * list = lv_obj_get_parent(obj);
    LV_UNUSED(list); /*If logging is disabled*/
    LV_LOG_USER("Clicked: %s", lv_list_get_button_text(list, obj));
}

/**
 * Simple navigation on a list widget
 */
void lv_example_gridnav_4(void)
{
    /*It's assumed that the default group is set and
     *there is a keyboard indev*/

    lv_obj_t * list = lv_list_create(lv_screen_active());
    lv_gridnav_add(list, LV_GRIDNAV_CTRL_ROLLOVER);
    lv_obj_align(list, LV_ALIGN_LEFT_MID, 10, 0);
    lv_group_add_obj(lv_group_get_default(), list);

    uint32_t i;
    for(i = 0; i < 20; i++) {
        char buf[32];

        /*Add some separators too, they are not focusable by gridnav*/
        if((i % 5) == 0) {
            lv_snprintf(buf, sizeof(buf), "Section %d", i / 5 + 1);
            lv_list_add_text(list, buf);
        }

        lv_snprintf(buf, sizeof(buf), "File %d", i + 1);
        lv_obj_t * item = lv_list_add_button(list, LV_SYMBOL_FILE, buf);
        lv_obj_add_event_cb(item, event_handler, LV_EVENT_CLICKED, NULL);
        lv_group_remove_obj(item);  /*The default group adds it automatically*/
    }

    lv_obj_t * btn = lv_button_create(lv_screen_active());
    lv_obj_align(btn, LV_ALIGN_RIGHT_MID, -10, 0);
    lv_obj_t * label = lv_label_create(btn);
    lv_label_set_text(label, "Button");
}

#endif

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API