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

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 file.*/
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.

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)
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 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_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

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)

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.