Add support for Views which are not components

2 files changed, 22 insertions, 14 deletions

diff --git a/server/src/main/java/com/vaadin/navigator/Navigator.java b/server/src/main/java/com/vaadin/navigator/Navigator.java
index 567c271211..2341479832 100644
--- a/server/src/main/java/com/vaadin/navigator/Navigator.java
+++ b/server/src/main/java/com/vaadin/navigator/Navigator.java
@@ -170,13 +170,8 @@ public class Navigator implements Serializable {
 
         @Override
         public void showView(View view) {
-            if (view instanceof Component) {
-                container.removeAllComponents();
-                container.addComponent((Component) view);
-            } else {
-                throw new IllegalArgumentException(
-                        "View is not a component: " + view);
-            }
+            container.removeAllComponents();
+            container.addComponent(view.getViewComponent());
         }
     }
 
@@ -204,12 +199,7 @@ public class Navigator implements Serializable {
 
         @Override
         public void showView(View view) {
-            if (view instanceof Component) {
-                container.setContent((Component) view);
-            } else {
-                throw new IllegalArgumentException(
-                        "View is not a component: " + view);
-            }
+            container.setContent(view.getViewComponent());
         }
     }
 
diff --git a/server/src/main/java/com/vaadin/navigator/View.java b/server/src/main/java/com/vaadin/navigator/View.java
index 8e083c6833..72e60dfdc4 100644
--- a/server/src/main/java/com/vaadin/navigator/View.java
+++ b/server/src/main/java/com/vaadin/navigator/View.java
@@ -25,7 +25,8 @@ import com.vaadin.ui.Component;
  * Interface for all views controlled by the navigator.
  *
  * Each view added to the navigator must implement this interface. Typically, a
- * view is a {@link Component}.
+ * view is a {@link Component}, if it is not then you should override
+ * {@link #getViewComponent()} to define the component to show for the view.
  *
  * @author Vaadin Ltd
  * @since 7.0
@@ -46,4 +47,21 @@ public interface View extends Serializable {
      *
      */
     public void enter(ViewChangeEvent event);
+
+    /**
+     * Gets the component to show when navigating to the view.
+     *
+     * By default casts this View to a {@link Component} if possible, otherwise
+     * throws an IllegalStateException.
+     *
+     * @since
+     * @return the component to show, by default the view instance itself
+     */
+    public default Component getViewComponent() {
+        if (!(this instanceof Component)) {
+            throw new IllegalStateException(
+                    "View is not a Component. Override getViewComponent() to return the root view component");
+        }
+        return (Component) this;
+    }
 }