Managing Menu and Back Key Events

The menu and back functions are common UX behaviors in applications. Generally, the user taps the Back hardware key to return to the previous screen. The applications also provide option menus to manipulate their functions through the Menu hardware key.

This feature is supported in mobile applications only.

Normally, the key events are only delivered to the object in focus. However, with the EFL Extension functions, you can let visible objects without focus get events from the Menu and Back keys.

Figure: Menu and Back keys

Menu and Back keys

The EFL Extension library maintains its own object stack to determine which object receives the event. Only visible objects are added to the stack.

The stack is based on Evas layers, which means that if 2 objects are registered for the same EFL Extension event, the object on the higher Evas layer gets the event. The following figure shows an example of objects on different layers. Objects 1, 2, and 3 are registered with EFL Extension callbacks for the same event, such as a Back key event. When the event occurs, object 3, which is on the highest layer (layer 3), gets the event callback.

Figure: Objects on different layers

Objects on different layers

If the objects with callbacks for the same event are on the same layer, the object which is registered the callback first gets the event.

To register a callback for the Menu or Back key, use the eext_object_event_callback_add() function with the application callback type:

  • EEXT_CALLBACK_BACK: Hardware Back key event
  • EEXT_CALLBACK_MORE: Hardware Menu key event

To delete a registered event in the EFL Extension, use the eext_object_event_callback_del() function.

The EFL Extension also provides other convenient functions to work with the Menu and Back keys for popup, ctxpopup, naviframe, and entry components.

Managing Hardware Key Events

The following example application has a window with a naviframe, and registers the EFL Extension Menu and Back key events for the naviframe. When the Menu key is pressed, the _create_popup() callback creates a popup and registers an EFL Extension Back key event for the popup. When the Back key is pressed:

  • If the popup is shown, the eext_popup_back_cb() callback registered for the popup is triggered, because the popup is located on a higher level than the naviframe. The callback removes the popup.
  • If the popup is not shown, the _nf_back_cb() callback registered for the naviframe is triggered. The callback hides the application.

To manage hardware key events:

  1. To use the functions and data types of the Efl Extension API, include the <efl_extension.h> header file in your application:

    #include <efl_extension.h>

  2. Create a window, naviframe, and label, and show the window:

    static void
create_base_gui(appdata_s *ad)
{
    Evas_Object *win = NULL;

    /* Create the window */
    win = elm_win_util_standard_add(NULL, "extension sample");
    evas_object_smart_callback_add(win, "delete,request", _win_del, NULL);

    /* Create the naviframe */
    Evas_Object *nf = NULL;
    nf = elm_naviframe_add(win);
    evas_object_size_hint_weight_set(win, EVAS_HINT_EXPAND, EVAS_HINT_EXPAND);
    elm_win_resize_object_add(win, nf);
    evas_object_show(nf);

    /* Create a label */
    Evas_Object *label = NULL;
    label = elm_label_add(nf);
    elm_object_text_set(label, "Press menu key to show popup,<br/>back key to exit.");
    elm_naviframe_item_push(nf, "Efl Extension usage", NULL, NULL, label, NULL);

    /* Show the window */
    evas_object_show(win);

  3. Register EFL Extension callbacks for the naviframe:

        /* Register the Menu key event callback */
    eext_object_event_callback_add(nf, EEXT_CALLBACK_MORE, _create_popup, NULL);
    /* Register the Back key event callback */
    eext_object_event_callback_add(nf, EEXT_CALLBACK_BACK, _nf_back_cb, win);
}

  4. In the Menu key callback, create a popup and register an EFL Extension Back key event callback for it:

    static void
_create_popup(void *data, Evas_Object *obj, void *event_info)
{
    Evas_Object *parent = obj;

    /* Create the popup */
    Evas_Object *popup = NULL, *content = NULL;
    popup = elm_popup_add(parent);
    elm_object_part_text_set(popup, "title,text", "Title");
    elm_popup_orient_set(popup, ELM_POPUP_ORIENT_CENTER);

    /* Add a label to the popup */
    content = elm_label_add(parent);
    elm_object_text_set(content, "Press back key to remove popup.");
    elm_object_content_set(popup, content);

    /* Register the Back key event callback */
    eext_object_event_callback_add(popup, EEXT_CALLBACK_BACK, eext_popup_back_cb, NULL);
    /* Show the popup */
    evas_object_show(popup);
}

  5. In the Back key callbacks:

    • The eext_popup_back_cb() callback is a macro function that removes the popup.

      To use a hide effect in dismissing the popup, use the elm_popup_dismiss() function in the callback:

      static void
eext_ctxpopup_back_cb(void *data EINA_UNUSED, Evas_Object *obj, void *event_info EINA_UNUSED)
{
    elm_ctxpopup_dismiss(obj);
}

    • To hide the application window, use the elm_win_lower() function in the _nf_back_cb() callback:

      static void
_nf_back_cb(void *data, Evas_Object *obj, void *event_info)
{
    Evas_Object *win = data;

    /* Hide the window */
    elm_win_lower(win);
}
  • Dependencies
    • Tizen 2.4 and Higher for Mobile
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