# Events (/examples/event)



Widgets emit events such as `LV_EVENT_CLICKED`, `LV_EVENT_VALUE_CHANGED`, `LV_EVENT_DRAW_MAIN`, and `LV_EVENT_KEY`. You register a callback with `lv_obj_add_event_cb()` and receive an `lv_event_t` pointer from which you read the code, target, and user data. The examples cover basic wiring, bubbling, custom event codes, and reading input device state inside a handler.

Event bubbling to a parent [#event-bubbling-to-a-parent]

<LvglExampleBrief>
  Handle clicks on child buttons from a single container callback.
</LvglExampleBrief>

A 290x200 container uses `LV_FLEX_FLOW_ROW_WRAP` and holds 30 small
buttons, each flagged with `LV_OBJ_FLAG_EVENT_BUBBLE`. One
`LV_EVENT_CLICKED` callback on the container reads
`lv_event_get_target_obj` to identify which button was clicked and paints
its background red; clicks on the container itself are ignored.

<LvglExample name="lv_example_event_bubble" path="event/lv_example_event_bubble" />

Handle multiple button events [#handle-multiple-button-events]

<LvglExampleBrief>
  Report the most recent button event on a second label.
</LvglExampleBrief>

A centered button with a `Click me!` label is paired with an info label
on the active screen. A single callback subscribed with `LV_EVENT_ALL`
switches on `lv_event_get_code` and writes the name of the latest event
(`LV_EVENT_PRESSED`, `LV_EVENT_CLICKED`, `LV_EVENT_LONG_PRESSED`,
`LV_EVENT_LONG_PRESSED_REPEAT`) into the info label.

<LvglExample name="lv_example_event_button" path="event/lv_example_event_button" />

Click event on a button [#click-event-on-a-button]

<LvglExampleBrief>
  Update a button's label with an incrementing counter on each click.
</LvglExampleBrief>

A button with a child label is placed on the active screen. An
`LV_EVENT_CLICKED` callback retrieves the button, updates its label with
a static incrementing counter, and logs `Clicked`.

<LvglExample name="lv_example_event_click" path="event/lv_example_event_click" />

Custom drawing on draw task events [#custom-drawing-on-draw-task-events]

<LvglExampleBrief>
  Draw a pulsing red circle on top of a container with a draw task callback.
</LvglExampleBrief>

A 200x200 container is centered and flagged with
`LV_OBJ_FLAG_SEND_DRAW_TASK_EVENTS`. An `LV_EVENT_DRAW_TASK_ADDED`
callback inspects the draw task and, when `base_dsc->part` is
`LV_PART_MAIN`, calls `lv_draw_rect` to paint a pink circle with a red
border and outline. A 30 ms `lv_timer_t` bounces a `size` counter between
0 and 50 and invalidates the container each tick to animate the circle.

<LvglExample name="lv_example_event_draw" path="event/lv_example_event_draw" />

Click streaks (single, double, triple) [#click-streaks-single-double-triple]

<LvglExampleBrief>
  React to single, double, and triple click events plus the short-click streak count.
</LvglExampleBrief>

A button is registered with four event callbacks: `LV_EVENT_SHORT_CLICKED`
reads `lv_indev_get_short_click_streak()` and writes the count to a
separate label; `LV_EVENT_SINGLE_CLICKED`, `LV_EVENT_DOUBLE_CLICKED`, and
`LV_EVENT_TRIPLE_CLICKED` each set the button's label to a matching string.

<LvglExample name="lv_example_event_streak" path="event/lv_example_event_streak" />

Event trickle to children [#event-trickle-to-children]

<LvglExampleBrief>
  Forward pressed state from a flex container down to its children.
</LvglExampleBrief>

A 290x200 container with `LV_FLEX_FLOW_ROW_WRAP` holds nine small
sub-containers, each with a numbered label. The container is flagged with
`LV_OBJ_FLAG_EVENT_TRICKLE` so its input events reach the children; a
single white-on-black style is added to the container for
`LV_STATE_PRESSED` and to each sub-container for `LV_STATE_FOCUSED`, so
pressing the container flips the whole group to the dark style.

<LvglExample name="lv_example_event_trickle" path="event/lv_example_event_trickle" />