Only show options menu of the active item in a ViewPager (#335)

conductor-modules/support/src/main/java/com/bluelinelabs/conductor/support/RouterPagerAdapter.java

@@ -30,6 +30,7 @@ public abstract class RouterPagerAdapter extends PagerAdapter {
     private SparseArray<Bundle> savedPages = new SparseArray<>();
     private SparseArray<Router> visibleRouters = new SparseArray<>();
     private ArrayList<Integer> savedPageHistory = new ArrayList<>();
+    private Router currentPrimaryRouter;
 
     /**
      * Creates a new RouterPagerAdapter using the passed host.
@@ -77,6 +78,12 @@ public abstract class RouterPagerAdapter extends PagerAdapter {
         router.rebindIfNeeded();
         configureRouter(router, position);
 
+        if (router != currentPrimaryRouter) {
+            for (RouterTransaction transaction : router.getBackstack()) {
+                transaction.controller().setOptionsMenuHidden(true);
+            }
+        }
+
         visibleRouters.put(position, router);
         return router;
     }
@@ -99,6 +106,24 @@ public abstract class RouterPagerAdapter extends PagerAdapter {
         visibleRouters.remove(position);
     }
 
+    @Override
+    public void setPrimaryItem(ViewGroup container, int position, Object object) {
+        Router router = (Router)object;
+        if (router != currentPrimaryRouter) {
+            if (currentPrimaryRouter != null) {
+                for (RouterTransaction transaction : currentPrimaryRouter.getBackstack()) {
+                    transaction.controller().setOptionsMenuHidden(true);
+                }
+            }
+            if (router != null) {
+                for (RouterTransaction transaction : router.getBackstack()) {
+                    transaction.controller().setOptionsMenuHidden(false);
+                }
+            }
+            currentPrimaryRouter = router;
+        }
+    }
+
     @Override
     public boolean isViewFromObject(View view, Object object) {
         Router router = (Router)object;