fixed #1368: Implement EffectsAdvancedTest (Effect4). Added some comments.

tests/tests/EffectsAdvancedTest/EffectsAdvancedTest.cpp

@@ -140,6 +140,11 @@ public:
         return pRet;
     }
 private:
+
+    Lens3DTarget()
+        : m_pLens3D(NULL)
+    {}
+
     CCLens3D* m_pLens3D;
 };
 
@@ -152,10 +157,17 @@ void Effect4::onEnter()
     CCActionInterval* move_back = move->reverse();
     CCActionInterval* seq = (CCActionInterval *)(CCSequence::create( move, move_back, NULL));
 
+    /* In cocos2d-iphone, the type of action's target is 'id', so it supports using the instance of 'CCLens3D' as its target.
+        While in cocos2d-x, the target of action only supports CCNode or its subclass,
+        so we make an encapsulation for CCLens3D to achieve that.
+    */
+
     CCDirector* director = CCDirector::sharedDirector();
     CCNode* pTarget = Lens3DTarget::create(lens);
+    // Please make sure the target been added to its parent.
+    this->addChild(pTarget);
+
     director->getActionManager()->addAction(seq, pTarget, false);
-    addChild(pTarget);
     this->runAction( lens );
 }