Grid navigation
Grid navigation (gridnav for short) is a feature that moves focus among a set of child Widgets via arrow-key presses.
If the child Widgets 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. This is useful, for example, to simplify navigation among items in a List Widget.
Gridnav assumes that the Widget to which gridnav is added is part of a group. This way, if the Widget with gridnav has focus, the arrow key presses are automatically forwarded to the Widget 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 gridnav behavior to any Widget (e.g. one serving as a container for child Widgets that the end user will navigate among using arrow keys) use lv_gridnav_add(container, flags).
The flags argument controls the navigation behavior:
LV_GRIDNAV_CTRL_NONE: Default settingsLV_GRIDNAV_CTRL_ROLLOVER: If there is no next/previous Widget in a direction, the focus goes to the Widget 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 Widget can be scrolled in that direction then it will be scrolled instead of going to the next/previous Widget. If there is no more room for scrolling the next/previous Widget will receive focus normally.LV_GRIDNAV_CTRL_HORIZONTAL_MOVE_ONLY: Only use the left/right keys for grid navigation. Up/down key events will be sent to the Widget that has focus.LV_GRIDNAV_CTRL_VERTICAL_MOVE_ONLY: Only use the up/down keys for grid navigation. Left/right key events will be sent to the Widget that has focus.
While the above behaviors can be combined by bit-wise OR-ing the above values together,
LV_GRIDNAV_CTRL_HORIZONTAL_MOVE_ONLY and LV_GRIDNAV_CTRL_VERTICAL_MOVE_ONLY
should not be used together.
lv_gridnav_remove(container) Removes gridnav behavior from a Widget.
Focusable Widgets
A Widget 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 receive focus via gridnav.
Examples
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
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
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 another 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 another 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
Grid navigation for only one axis
C code
View on GitHub#include "../../lv_examples.h"
#if LV_USE_GRIDNAV && LV_USE_FLEX && LV_BUILD_EXAMPLES
static const char * opts[] = {"0\n1\n2\n3\n4\n5", "0\n1\n2\n3\n4\n5\n6\n7\n8\n9", "s\nm\nh"};
static const int32_t opts_counts[] = {6, 10, 3};
static lv_obj_t * sliders[3];
static lv_obj_t * rollers[3];
static void slider_key_cb(lv_event_t * e)
{
uint8_t i = (uint32_t)(uintptr_t)lv_event_get_user_data(e);
lv_roller_set_selected(rollers[i], lv_slider_get_value(sliders[i]), LV_ANIM_ON);
}
static void roller_key_cb(lv_event_t * e)
{
uint8_t i = (uint32_t)(uintptr_t)lv_event_get_user_data(e);
lv_slider_set_value(sliders[i], lv_roller_get_selected(rollers[i]), LV_ANIM_ON);
}
/**
* Grid navigation for only one axis
*/
void lv_example_gridnav_5(void)
{
/*It's assumed that the default group is set and
*there is a keyboard indev*/
lv_group_t * group = lv_group_get_default();
lv_obj_t * cont;
cont = lv_obj_create(lv_screen_active());
lv_obj_set_flex_flow(cont, LV_FLEX_FLOW_COLUMN);
lv_obj_set_flex_align(cont, LV_FLEX_ALIGN_CENTER, LV_FLEX_ALIGN_CENTER, LV_FLEX_ALIGN_CENTER);
lv_obj_set_size(cont, lv_pct(100), lv_pct(50));
lv_obj_align(cont, LV_ALIGN_TOP_MID, 0, 0);
/* only up/down keys will be used for grid navigation in this container. */
/* left/right will be sent to the sliders */
lv_gridnav_add(cont, LV_GRIDNAV_CTRL_VERTICAL_MOVE_ONLY);
lv_group_add_obj(group, cont);
for(uint32_t i = 0; i < 3; i++) {
lv_obj_t * slider = lv_slider_create(cont);
lv_slider_set_range(slider, 0, opts_counts[i] - 1);
lv_group_remove_obj(slider);
lv_obj_set_width(slider, lv_pct(85));
sliders[i] = slider;
lv_obj_add_event_cb(slider, slider_key_cb, LV_EVENT_KEY, (void *)(uintptr_t)i);
}
cont = lv_obj_create(lv_screen_active());
lv_obj_set_flex_flow(cont, LV_FLEX_FLOW_ROW);
lv_obj_set_flex_align(cont, LV_FLEX_ALIGN_CENTER, LV_FLEX_ALIGN_CENTER, LV_FLEX_ALIGN_CENTER);
lv_obj_set_size(cont, lv_pct(100), lv_pct(50));
lv_obj_align(cont, LV_ALIGN_BOTTOM_MID, 0, 0);
/* only left/right keys will be used for grid navigation in this container. */
/* up/down will be sent to the rollers */
lv_gridnav_add(cont, LV_GRIDNAV_CTRL_HORIZONTAL_MOVE_ONLY);
lv_group_add_obj(group, cont);
for(uint32_t i = 0; i < 3; i++) {
lv_obj_t * roller = lv_roller_create(cont);
lv_roller_set_options(roller, opts[i], LV_ROLLER_MODE_INFINITE);
lv_obj_set_size(roller, lv_pct(30), lv_pct(100));
lv_group_remove_obj(roller);
rollers[i] = roller;
lv_obj_add_event_cb(roller, roller_key_cb, LV_EVENT_KEY, (void *)(uintptr_t)i);
}
}
#endif