Input devices¶

An input device usually means:

Pointer-like input device like touchpad or mouse
Keypads like a normal keyboard or simple numeric keypad
Encoders with left/right turn and push options
External hardware buttons which are assigned to specific points on the screen

Important

Before reading further, please read the [Porting](/porting/indev) section of Input devices

Pointers¶

Cursor¶

Pointer input devices (like a mouse) can have a cursor.

...
lv_indev_t * mouse_indev = lv_indev_drv_register(&indev_drv);

LV_IMG_DECLARE(mouse_cursor_icon);                          /*Declare the image source.*/
lv_obj_t * cursor_obj = lv_img_create(lv_scr_act());       /*Create an image object for the cursor */
lv_img_set_src(cursor_obj, &mouse_cursor_icon);             /*Set the image source*/
lv_indev_set_cursor(mouse_indev, cursor_obj);               /*Connect the image  object to the driver*/

Note that the cursor object should have lv_obj_clear_flag(cursor_obj, LV_OBJ_FLAG_CLICKABLE). For images, clicking is disabled by default.

Gestures¶

Pointer input devices can detect basic gestures. By default, most of the widgets send the gestures to its parent, so finally the gestures can be detected on the screen object in a form of an LV_EVENT_GESTURE event. For example:

void my_event(lv_event_t * e)
{
  lv_obj_t * screen = lv_event_get_current_target(e);
  lv_dir_t dir = lv_indev_get_gesture_dir(lv_indev_act());
  switch(dir) {
    case LV_DIR_LEFT:
      ...
      break;
    case LV_DIR_RIGHT:
      ...
      break;
    case LV_DIR_TOP:
      ...
      break;
    case LV_DIR_BOTTOM:
      ...
      break;
  }
}

...

lv_obj_add_event_cb(screen1, my_event, LV_EVENT_GESTURE, NULL);

To prevent passing the gesture event to the parent from an object use lv_obj_clear_flag(obj, LV_OBJ_FLAG_GESTURE_BUBBLE).

Note that, gestures are not triggered if an object is being scrolled.

If you did some action on a gesture you can call lv_indev_wait_release(lv_indev_get_act()) in the event handler to prevent LVGL sending further input device related events.

Keypad and encoder¶

You can fully control the user interface without a touchpad or mouse by using a keypad or encoder(s). It works similar to the TAB key on the PC to select an element in an application or a web page.

Groups¶

Objects you want to control with a keypad or encoder need to be added to a Group. In every group there is exactly one focused object which receives the pressed keys or the encoder actions. For example, if a Text area is focused and you press some letter on a keyboard, the keys will be sent and inserted into the text area. Similarly, if a Slider is focused and you press the left or right arrows, the slider's value will be changed.

You need to associate an input device with a group. An input device can send key events to only one group but a group can receive data from more than one input device.

To create a group use lv_group_t * g = lv_group_create() and to add an object to the group use lv_group_add_obj(g, obj).

To associate a group with an input device use lv_indev_set_group(indev, g), where indev is the return value of lv_indev_drv_register()

Keys¶

There are some predefined keys which have special meaning:

LV_KEY_NEXT Focus on the next object
LV_KEY_PREV Focus on the previous object
LV_KEY_ENTER Triggers LV_EVENT_PRESSED/CLICKED/LONG_PRESSED etc. events
LV_KEY_UP Increase value or move upwards
LV_KEY_DOWN Decrease value or move downwards
LV_KEY_RIGHT Increase value or move to the right
LV_KEY_LEFT Decrease value or move to the left
LV_KEY_ESC Close or exit (E.g. close a Drop down list)
LV_KEY_DEL Delete (E.g. a character on the right in a Text area)
LV_KEY_BACKSPACE Delete a character on the left (E.g. in a Text area)
LV_KEY_HOME Go to the beginning/top (E.g. in a Text area)
LV_KEY_END Go to the end (E.g. in a Text area)

The most important special keys are LV_KEY_NEXT/PREV, LV_KEY_ENTER and LV_KEY_UP/DOWN/LEFT/RIGHT. In your read_cb function, you should translate some of your keys to these special keys to support navigation in a group and interact with selected objects.

Usually, it's enough to use only LV_KEY_LEFT/RIGHT because most objects can be fully controlled with them.

With an encoder you should use only LV_KEY_LEFT, LV_KEY_RIGHT, and LV_KEY_ENTER.

Edit and navigate mode¶

Since a keypad has plenty of keys, it's easy to navigate between objects and edit them using the keypad. But encoders have a limited number of "keys" and hence it is difficult to navigate using the default options. Navigate and Edit modes are used to avoid this problem with encoders.

In Navigate mode, an encoder's LV_KEY_LEFT/RIGHT is translated to LV_KEY_NEXT/PREV. Therefore, the next or previous object will be selected by turning the encoder. Pressing LV_KEY_ENTER will change to Edit mode.

In Edit mode, LV_KEY_NEXT/PREV is usually used to modify an object. Depending on the object's type, a short or long press of LV_KEY_ENTER changes back to Navigate mode. Usually, an object which cannot be pressed (like a Slider) leaves Edit mode upon a short click. But with objects where a short click has meaning (e.g. Button), a long press is required.

Default group¶

Interactive widgets - such as buttons, checkboxes, sliders, etc. - can be automatically added to a default group. Just create a group with lv_group_t * g = lv_group_create(); and set the default group with lv_group_set_default(g);

Don't forget to assign one or more input devices to the default group with lv_indev_set_group(my_indev, g);.

Styling¶

If an object is focused either by clicking it via touchpad or focused via an encoder or keypad it goes to the LV_STATE_FOCUSED state. Hence, focused styles will be applied to it.

If an object switches to edit mode it enters the LV_STATE_FOCUSED | LV_STATE_EDITED states so these style properties will be shown.

For a more detailed description read the Style section.

API¶

Input device¶

Functions

void lv_indev_read_timer_cb(lv_timer_t *timer)¶

Called periodically to read the input devices

Parameters: timer -- pointer to a timer to read

void lv_indev_enable(lv_indev_t *indev, bool en)¶

Enable or disable one or all input devices (default enabled)

Parameters

indev -- pointer to an input device or NULL to enable/disable all of them
en -- true to enable, false to disable

lv_indev_t *lv_indev_get_act(void)¶

Get the currently processed input device. Can be used in action functions too.

Returns: pointer to the currently processed input device or NULL if no input device processing right now

lv_indev_type_t lv_indev_get_type(const lv_indev_t *indev)¶

Get the type of an input device

Parameters: indev -- pointer to an input device
Returns: the type of the input device from lv_hal_indev_type_t (LV_INDEV_TYPE_...)

void lv_indev_reset(lv_indev_t *indev, lv_obj_t *obj)¶

Reset one or all input devices

Parameters

indev -- pointer to an input device to reset or NULL to reset all of them
obj -- pointer to an object which triggers the reset.

void lv_indev_reset_long_press(lv_indev_t *indev)¶

Reset the long press state of an input device

Parameters: indev -- pointer to an input device

void lv_indev_set_cursor(lv_indev_t *indev, lv_obj_t *cur_obj)¶

Set a cursor for a pointer input device (for LV_INPUT_TYPE_POINTER and LV_INPUT_TYPE_BUTTON)

Parameters

indev -- pointer to an input device
cur_obj -- pointer to an object to be used as cursor

void lv_indev_set_group(lv_indev_t *indev, lv_group_t *group)¶

Set a destination group for a keypad input device (for LV_INDEV_TYPE_KEYPAD)

Parameters

indev -- pointer to an input device
group -- point to a group

void lv_indev_set_button_points(lv_indev_t *indev, const lv_point_t points[])¶

Set the an array of points for LV_INDEV_TYPE_BUTTON. These points will be assigned to the buttons to press a specific point on the screen

Parameters

indev -- pointer to an input device
group -- point to a group

void lv_indev_get_point(const lv_indev_t *indev, lv_point_t *point)¶

Get the last point of an input device (for LV_INDEV_TYPE_POINTER and LV_INDEV_TYPE_BUTTON)

Parameters

indev -- pointer to an input device
point -- pointer to a point to store the result

lv_dir_t lv_indev_get_gesture_dir(const lv_indev_t *indev)¶

Get the current gesture direct

Parameters: indev -- pointer to an input device
Returns: current gesture direct

uint32_t lv_indev_get_key(const lv_indev_t *indev)¶

Get the last pressed key of an input device (for LV_INDEV_TYPE_KEYPAD)

Parameters: indev -- pointer to an input device
Returns: the last pressed key (0 on error)

lv_dir_t lv_indev_get_scroll_dir(const lv_indev_t *indev)¶

Check the current scroll direction of an input device (for LV_INDEV_TYPE_POINTER and LV_INDEV_TYPE_BUTTON)

Parameters: indev -- pointer to an input device
Returns: LV_DIR_NONE: no scrolling now LV_DIR_HOR/VER

lv_obj_t *lv_indev_get_scroll_obj(const lv_indev_t *indev)¶

Get the currently scrolled object (for LV_INDEV_TYPE_POINTER and LV_INDEV_TYPE_BUTTON)

Parameters: indev -- pointer to an input device
Returns: pointer to the currently scrolled object or NULL if no scrolling by this indev

void lv_indev_get_vect(const lv_indev_t *indev, lv_point_t *point)¶

Get the movement vector of an input device (for LV_INDEV_TYPE_POINTER and LV_INDEV_TYPE_BUTTON)

Parameters

indev -- pointer to an input device
point -- pointer to a point to store the types.pointer.vector

void lv_indev_wait_release(lv_indev_t *indev)¶

Do nothing until the next release

Parameters: indev -- pointer to an input device

lv_obj_t *lv_indev_get_obj_act(void)¶

Gets a pointer to the currently active object in the currently processed input device.

Returns: pointer to currently active object or NULL if no active object

lv_timer_t *lv_indev_get_read_timer(lv_disp_t *indev)¶

Get a pointer to the indev read timer to modify its parameters with lv_timer_... functions.

Parameters: indev -- pointer to an input device
Returns: pointer to the indev read refresher timer. (NULL on error)

lv_obj_t *lv_indev_search_obj(lv_obj_t *obj, lv_point_t *point)¶

Search the most top, clickable object by a point

Parameters

obj -- pointer to a start object, typically the screen
point -- pointer to a point for searching the most top child

Returns

pointer to the found object or NULL if there was no suitable object

Groups¶

Typedefs

typedef uint8_t lv_key_t¶

typedef void (*lv_group_focus_cb_t)(struct _lv_group_t*)¶

typedef void (*lv_group_edge_cb_t)(struct _lv_group_t*, bool)¶

typedef struct _lv_group_t lv_group_t¶: Groups can be used to logically hold objects so that they can be individually focused. They are NOT for laying out objects on a screen (try layouts for that).

Enums

enum [anonymous]¶

Values:

enumerator LV_KEY_UP¶

enumerator LV_KEY_DOWN¶

enumerator LV_KEY_RIGHT¶

enumerator LV_KEY_LEFT¶

enumerator LV_KEY_ESC¶

enumerator LV_KEY_DEL¶

enumerator LV_KEY_BACKSPACE¶

enumerator LV_KEY_ENTER¶

enumerator LV_KEY_NEXT¶

enumerator LV_KEY_PREV¶

enumerator LV_KEY_HOME¶

enumerator LV_KEY_END¶

enum lv_group_refocus_policy_t¶

Values:

enumerator LV_GROUP_REFOCUS_POLICY_NEXT¶

enumerator LV_GROUP_REFOCUS_POLICY_PREV¶

Functions

void _lv_group_init(void)¶

Init. the group module

Remark: Internal function, do not call directly.

lv_group_t *lv_group_create(void)¶

Create a new object group

Returns: pointer to the new object group

void lv_group_del(lv_group_t *group)¶

Delete a group object

Parameters: group -- pointer to a group

void lv_group_set_default(lv_group_t *group)¶

Set a default group. New object are added to this group if it's enabled in their class with add_to_def_group = true

Parameters: group -- pointer to a group (can be NULL)

lv_group_t *lv_group_get_default(void)¶

Get the default group

Returns: pointer to the default group

void lv_group_add_obj(lv_group_t *group, struct _lv_obj_t *obj)¶

Add an object to a group

Parameters

group -- pointer to a group
obj -- pointer to an object to add

void lv_group_swap_obj(struct _lv_obj_t *obj1, struct _lv_obj_t *obj2)¶

Swap 2 object in a group. The object must be in the same group

Parameters

obj1 -- pointer to an object
obj2 -- pointer to an other object

void lv_group_remove_obj(struct _lv_obj_t *obj)¶

Remove an object from its group

Parameters: obj -- pointer to an object to remove

void lv_group_remove_all_objs(lv_group_t *group)¶

Remove all objects from a group

Parameters: group -- pointer to a group

void lv_group_focus_obj(struct _lv_obj_t *obj)¶

Focus on an object (defocus the current)

Parameters: obj -- pointer to an object to focus on

void lv_group_focus_next(lv_group_t *group)¶

Focus the next object in a group (defocus the current)

Parameters: group -- pointer to a group

void lv_group_focus_prev(lv_group_t *group)¶

Focus the previous object in a group (defocus the current)

Parameters: group -- pointer to a group

void lv_group_focus_freeze(lv_group_t *group, bool en)¶

Do not let to change the focus from the current object

Parameters

group -- pointer to a group
en -- true: freeze, false: release freezing (normal mode)

lv_res_t lv_group_send_data(lv_group_t *group, uint32_t c)¶

Send a control character to the focuses object of a group

Parameters

group -- pointer to a group
c -- a character (use LV_KEY_.. to navigate)

Returns

result of focused object in group.

void lv_group_set_focus_cb(lv_group_t *group, lv_group_focus_cb_t focus_cb)¶

Set a function for a group which will be called when a new object is focused

Parameters

group -- pointer to a group
focus_cb -- the call back function or NULL if unused

void lv_group_set_edge_cb(lv_group_t *group, lv_group_edge_cb_t edge_cb)¶

Set a function for a group which will be called when a focus edge is reached

Parameters

group -- pointer to a group
edge_cb -- the call back function or NULL if unused

void lv_group_set_refocus_policy(lv_group_t *group, lv_group_refocus_policy_t policy)¶

Set whether the next or previous item in a group is focused if the currently focused obj is deleted.

Parameters

group -- pointer to a group
policy -- new refocus policy enum

void lv_group_set_editing(lv_group_t *group, bool edit)¶

Manually set the current mode (edit or navigate).

Parameters

group -- pointer to group
edit -- true: edit mode; false: navigate mode

void lv_group_set_wrap(lv_group_t *group, bool en)¶

Set whether focus next/prev will allow wrapping from first->last or last->first object.

Parameters

group -- pointer to group
en -- true: wrapping enabled; false: wrapping disabled

struct _lv_obj_t *lv_group_get_focused(const lv_group_t *group)¶

Get the focused object or NULL if there isn't one

Parameters: group -- pointer to a group
Returns: pointer to the focused object

lv_group_focus_cb_t lv_group_get_focus_cb(const lv_group_t *group)¶

Get the focus callback function of a group

Parameters: group -- pointer to a group
Returns: the call back function or NULL if not set

lv_group_edge_cb_t lv_group_get_edge_cb(const lv_group_t *group)¶

Get the edge callback function of a group

Parameters: group -- pointer to a group
Returns: the call back function or NULL if not set

bool lv_group_get_editing(const lv_group_t *group)¶

Get the current mode (edit or navigate).

Parameters: group -- pointer to group
Returns: true: edit mode; false: navigate mode

bool lv_group_get_wrap(lv_group_t *group)¶

Get whether focus next/prev will allow wrapping from first->last or last->first object.

Parameters

group -- pointer to group
en -- true: wrapping enabled; false: wrapping disabled

uint32_t lv_group_get_obj_count(lv_group_t *group)¶

Get the number of object in the group

Parameters: group -- pointer to a group
Returns: number of objects in the group

struct _lv_group_t¶

#include <lv_group.h>

Groups can be used to logically hold objects so that they can be individually focused. They are NOT for laying out objects on a screen (try layouts for that).

Public Members

lv_ll_t obj_ll¶: Linked list to store the objects in the group

struct _lv_obj_t **obj_focus¶: The object in focus

lv_group_focus_cb_t focus_cb¶: A function to call when a new object is focused (optional)

lv_group_edge_cb_t edge_cb¶: A function to call when an edge is reached, no more focus targets are available in this direction (to allow edge feedback like a sound or a scroll bounce)

void *user_data¶

uint8_t frozen¶: 1: can't focus to new object

uint8_t editing¶: 1: Edit mode, 0: Navigate mode

uint8_t refocus_policy¶: 1: Focus prev if focused on deletion. 0: Focus next if focused on deletion.

uint8_t wrap¶: 1: Focus next/prev can wrap at end of list. 0: Focus next/prev stops at end of list.