This is a demo of two-level expandable app bar. In the first level, it shows an image like the
regular usage of CollapsingToolbarLayout. When user tapping or scrolling down on the semi-expanded
toolbar, it will further expand the toolbar to show some detail information in a NestedScrollView.
When the toolbar is fully expanded, user may scroll to the bottom of the text or tap
the close button to collapse the toolbar.
I used CollapsingToolbarLayout from Android Design Support Library as the base and add different
listeners/detectors to detect scroll and tap events.
Watch the demo video for details.