Keypad and Keyboard¶

Overview¶

Full keyboards with all the letters or simple keypads with a few navigation buttons belong in the Keypad category.

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

Only widgets added to a group can be selected by a keyboard. Learn more at Groups.

Example¶

/*Create a group and add widgets to it so they can be selected by the keypad*/
lv_group_t * g = lv_group_create();

lv_indev_t * indev = lv_indev_create();
lv_indev_set_type(indev, LV_INDEV_TYPE_KEYPAD);
lv_indev_set_read_cb(indev, keyboard_read);
lv_indev_set_group(indev, g);

...

void keyboard_read(lv_indev_t * indev, lv_indev_data_t * data) {
  if(key_pressed()) {
     data->key = my_last_key();            /* Get the last pressed or released key */
     data->state = LV_INDEV_STATE_PRESSED;
  } else {
     data->state = LV_INDEV_STATE_RELEASED;
  }
}

Keys¶

There are some predefined keys which have special meaning:

LV_KEY_NEXT: Move focus to the next object
LV_KEY_PREV: Move focus to the previous object
LV_KEY_ENTER: Triggers LV_EVENT_PRESSED, LV_EVENT_CLICKED, or LV_EVENT_LONG_PRESSED events
LV_KEY_UP: Increase value or move up
LV_KEY_DOWN: Decrease value or move down
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 (e.g., a character on the left 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 in your read_cb() function are:

You should translate some of the read keys to these special keys to support navigation in a group and interact with selected widgets.