Only switch to main screen when the signed in account changes

use Multiplayer.EXTRA_INVITATION when retrieving an invitiation

Addresses both issues in #264

Change-Id: I8c3c9673bccad6d05e056b8583eb3d8cb89452c6

Author: mwgray

ButtonClicker/src/main/java/com/google/example/games/bc/MainActivity.java

@@ -639,6 +639,8 @@ public void onSuccess(Player player) {
             }
           }
       );
+
+      switchToMainScreen();
     }
 
     // register listener so we are notified if we receive an invitation to play
@@ -654,7 +656,7 @@ public void onSuccess(Player player) {
           public void onSuccess(Bundle hint) {
             if (hint != null) {
               Invitation invitation =
-                  hint.getParcelable(Multiplayer.EXTRA_TURN_BASED_MATCH);
+                  hint.getParcelable(Multiplayer.EXTRA_INVITATION);
 
               if (invitation != null && invitation.getInvitationId() != null) {
                 // retrieve and cache the invitation ID
@@ -665,8 +667,6 @@ public void onSuccess(Bundle hint) {
           }
         })
         .addOnFailureListener(createFailureListener("There was a problem getting the activation hint!"));
-
-    switchToMainScreen();
   }
 
   private OnFailureListener createFailureListener(final String string) {