Add an Helper in UIElement that converts lvgl object into UIElements or children via a static cast.

Make Tabview a friend of Base Page to allow it to notify pages that they are hidden or showing.

Implement the notification in Tabview to allow pages to know they are showing.

Platformio/OmoteUI/core/UIElement.hpp

@@ -26,6 +26,8 @@ public:
 
   ID GetID() { return mId; };
 
+  template <class UIElemTy> static UIElemTy GetElement(lv_obj_t *aLvglObject);
+
 protected:
   /// @brief get Lvgl object refernce to use in LVGL APIs
   /// @return lvgl object a
@@ -44,4 +46,26 @@ private:
   lv_obj_t *mLvglSelf;
   const ID mId;
 };
+
+/**
+ * @brief This helper allows conversion between anLvglObject and a
+ *        core element by using the user data that links the LVGL object
+ *        to its C++ counterpart. Do note that it is possible that this
+ *        user data is not always there if the Lvgl Object has not been wrapped
+ *        by UIElement
+ *
+ * @tparam UIElemTy - Type of element you want to cast to
+ * @param aLvglObject - object to extract User data from
+ * @return UIElemTy - object stored in user data (See constructor of
+ * UIElement)
+ */
+template <class UIElemTy>
+UIElemTy UIElement::GetElement(lv_obj_t *aLvglObject) {
+  auto UIElement = lv_obj_get_user_data(aLvglObject);
+  if (UIElement) {
+    return static_cast<UIElemTy>(UIElement);
+  }
+  return nullptr;
+}
+
 } // namespace UI

Platformio/OmoteUI/core/page/PageBase.hpp

@@ -3,9 +3,11 @@
 #include "WidgetBase.hpp"
 
 #include <vector>
-
 namespace UI::Page {
+class TabView;
 class Base : public UIElement {
+  friend TabView; // Allow Tab view to call OnShow and OnHide Since it can show
+                  // and Hide pages by swiping
 public:
   typedef std::unique_ptr<Base> Ptr;
 

Platformio/OmoteUI/core/page/TabView.cpp

@@ -7,7 +7,10 @@ using namespace UI::Page;
 TabView::TabView(ID aId)
     : Base(lv_tabview_create(Screen::BackgroundScreen::getLvInstance(),
                              LV_DIR_TOP, 0),
-           aId) {}
+           aId) {
+  lv_obj_add_event_cb(LvglSelf(), HandleTabChangeImpl, LV_EVENT_VALUE_CHANGED,
+                      nullptr);
+}
 
 void TabView::AddTab(Page::Base::Ptr aPage, std::string aTitle) {
   auto tab = std::make_unique<Base>(
@@ -16,4 +19,30 @@ void TabView::AddTab(Page::Base::Ptr aPage, std::string aTitle) {
   tab->AddElement(aPage.get());
 
   mTabs.push_back(std::move(tab));
+}
+
+uint16_t TabView::GetCurrentTabIdx() {
+  return lv_tabview_get_tab_act(LvglSelf());
+}
+
+void TabView::SetCurrentTabIdx(uint16_t aTabToSetActive,
+                               lv_anim_enable_t aIsDoAnimation) {
+  lv_tabview_set_act(LvglSelf(), aTabToSetActive, aIsDoAnimation);
+}
+
+void TabView::HandleTabChange() {
+  // Call OnShow() for the page we just swapped to in order to
+  // Notify the page that it is now showing and the other that the are now
+  // hidden
+  for (int i = 0; i < mTabs.size(); i++) {
+    GetCurrentTabIdx() == i ? mTabs[i]->OnShow() : mTabs[i]->OnHide();
+  }
+}
+
+void TabView::HandleTabChangeImpl(lv_event_t *aTabChangeEvent) {
+  auto self =
+      UIElement::GetElement<TabView *>(lv_event_get_target(aTabChangeEvent));
+  if (self) {
+    self->HandleTabChange();
+  }
 }

Platformio/OmoteUI/core/page/TabView.hpp

@@ -7,11 +7,18 @@ public:
   TabView(ID aId);
   void AddTab(Page::Base::Ptr aPage, std::string aTitle);
 
+  uint16_t GetCurrentTabIdx();
+  void SetCurrentTabIdx(uint16_t aTabToSetActive,
+                        lv_anim_enable_t aIsDoAnimation = LV_ANIM_ON);
+
 protected:
   void OnShow() {}
   void OnHide() {}
 
 private:
+  void HandleTabChange();
+  static void HandleTabChangeImpl(lv_event_t *aTabChangeEvent);
+
   std::vector<Page::Base::Ptr> mTabs;
 };