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Android Animations and Transitions The Transitions Framework Transitioning Back and Forth

Leonardo Fettucciari
Leonardo Fettucciari
633 Points

TransitionManager.setTransition(), why used twice here?

Hi, I don't understand why we added these two lines of code in this same place, wouldn't they override themselves?

What's really happening behind the scenes in this couple of lines?

private void setupTransitions() {
[...]
// Expanded scene
[...]
// Collapsed scene
[...]
        mTransitionManager.setTransition(mExpandedScene, mCollapsedScene, collapseTransitionSet);
        mTransitionManager.setTransition(mCollapsedScene, mExpandedScene, expandTransitionSet);
    }

1 Answer

I think of the transitionManager as a sort of librarian, just keeping track of the different "books". When you need a transition, you go to the librarian and ask for the one you need, and they give it to you. The transition actually happens in this code:

    @OnClick(R.id.track_panel)
    public void onTrackPanelClicked(View view) {
        if (mCurrentScene == mExpandedScene) {
            mCurrentScene = mCollapsedScene;
        } else {
            mCurrentScene = mExpandedScene;
        }
        mTransitionManager.transitionTo(mCurrentScene);
    }

You can see that this method first figures out "where you are" and then asks mTransitionManager to get us to "the other place".

[MOD: edited code block and marked thread resolved]