Button Click Method not working Confusing

public class MainActivity extends Activity {

    protected TransitionManager mTransitionManager;
    protected Scene mScene1;
    protected Scene mScene2;
    protected Scene mCurrentScene;
    protected TransitionSet mForwardSet;
    protected TransitionSet mBackwardSet;

    // Some code omitted for brevity

    public void onButtonClicked(View view) {
        if (mCurrentScene == mScene1) {

            mCurrentScene = mScene2;
        }
        else {
            mCurrentScene = mScene1;

        }
        mTransitionManager.setTransition(mCurrentScene);


    }

    protected void setupTransitions() {
        // These methods are setting up scenes and transitions sets like in the video
        initScenes();
        initSets(); 

        // Start here!
      mTransitionManager = new TransitionManager();
      mTransitionManager.setTransition(mScene1,mScene2,mForwardSet);
      mTransitionManager.setTransition(mScene2,mScene1,mBackwardSet);
      mScene1.enter();

    }
}