fix: fallback to legacy demo

Author: javier-godoy

src/main/java/com/flowingcode/vaadin/addons/demo/RouteTabs.java

@@ -36,8 +36,15 @@ public void add(RouterLink routerLink) {
 
   @Override
   public void beforeEnter(BeforeEnterEvent event) {
-    // In case no tabs will match
     setSelectedTab(null);
+    if (TabbedDemo.class.isAssignableFrom(event.getNavigationTarget())) {
+      RouterLink first = getFirstRoute();
+      if (first != null) {
+        event.forwardTo(first.getHref());
+      } else {
+        getChildren().findFirst().ifPresent(tab -> setSelectedTab((Tab) tab));
+      }
+    }
   }
 
   public Map<RouterLink, Tab> getRouterLinkTabMap() {

src/main/java/com/flowingcode/vaadin/addons/demo/TabbedDemo.java

@@ -29,16 +29,14 @@
 import com.vaadin.flow.component.orderedlayout.HorizontalLayout;
 import com.vaadin.flow.component.orderedlayout.VerticalLayout;
 import com.vaadin.flow.component.splitlayout.SplitLayout.Orientation;
-import com.vaadin.flow.router.BeforeEnterEvent;
-import com.vaadin.flow.router.BeforeEnterObserver;
 import com.vaadin.flow.router.PageTitle;
 import com.vaadin.flow.router.Route;
 import com.vaadin.flow.router.RouterLayout;
 import com.vaadin.flow.router.RouterLink;
 
 @StyleSheet("context://frontend/styles/commons-demo/shared-styles.css")
 @SuppressWarnings("serial")
-public class TabbedDemo extends VerticalLayout implements RouterLayout, BeforeEnterObserver {
+public class TabbedDemo extends VerticalLayout implements RouterLayout {
 
   private RouteTabs tabs;
   private HorizontalLayout footer;
@@ -192,14 +190,4 @@ private void updateSplitterOrientation() {
     }
   }
 
-  @Override
-  public void beforeEnter(BeforeEnterEvent event) {
-    if(TabbedDemo.class.isAssignableFrom(event.getNavigationTarget())) {
-      RouterLink first = tabs.getFirstRoute();
-      if(first != null) {
-        event.forwardTo(first.getHref()); 
-      }       
-    }
-  }
- 
 }