Allow to set the default focus in FocusArea dynamically

Fixes: 173464102
Test: manual
Change-Id: I79dce48f59c0f8af2e1d828674bd1431b1bb9365
diff --git a/car-ui-lib/car-ui-lib/src/main/java/com/android/car/ui/FocusArea.java b/car-ui-lib/car-ui-lib/src/main/java/com/android/car/ui/FocusArea.java
index b380e35..0488d28 100644
--- a/car-ui-lib/car-ui-lib/src/main/java/com/android/car/ui/FocusArea.java
+++ b/car-ui-lib/car-ui-lib/src/main/java/com/android/car/ui/FocusArea.java
@@ -720,6 +720,11 @@
         mBottomOffset = bottom;
     }
 
+    /** Sets the default focus view in this FocusArea. */
+    public void setDefaultFocus(@NonNull View defaultFocus) {
+        mDefaultFocusView = defaultFocus;
+    }
+
     @VisibleForTesting
     void enableForegroundHighlight() {
         mEnableForegroundHighlight = true;