Welcome to the Treehouse Community

The Treehouse Community is a meeting place for developers, designers, and programmers of all backgrounds and skill levels to get support. Collaborate here on code errors or bugs that you need feedback on, or asking for an extra set of eyes on your latest project. Join thousands of Treehouse students and alumni in the community today. (Note: Only Treehouse students can comment or ask questions, but non-students are welcome to browse our conversations.)

Looking to learn something new?

Treehouse offers a seven day free trial for new students. Get access to thousands of hours of content and a supportive community. Start your free trial today.

Android Animations and Transitions The Transitions Framework Transitioning Back and Forth

michael lee
michael lee
5,179 Points

Make sure you include both the forward set and the backward set!

this is challenge 2 of 4 and I think I've included both sets? but this error message pops up

MainActivity.java
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 == mScene2) {
            mCurrentScene = mScene1;
        }
        else {
            mCurrentScene = mScene2;
        }
        mTransitionManager.transitionTo(mCurrentScene);
    }

    protected void setupTransitions() {
        // These methods are setting up scenes and transitions sets like in the video
        initScenes();
        initSets(); 
      mTransitionManager = new TransitionManager();
        // Start here!

        TransitionSet mForwardSet = new TransitionSet();
      TransitionSet mBackwardSet = new TransitionSet();
      //Expanded Scene

        mTransitionManager.setTransition(mScene1, mScene2, mBackwardSet);
        mTransitionManager.setTransition(mScene2, mScene1, mForwardSet);
        mScene2.enter();

    }
}