I would like my activity's Toolbar to smoothly scroll out as a given scrollview grows, and then smoothly scroll back in if the user scrolls down. I.e. the basic scroll|enterAlways behaviour from e.g. this answer.
However, my layout has some layers between the CoordinatorLayout containing the Toolbar, and the ScrollView that should be driving everything. Unlike in this answer, I'd like to have the following layout:
CoordinatorLayout
AppBarLayout
Toolbar
LinearLayout [vertical]
LinearLayout [vertical]
ImageView
ScrollView
The seemingly redundant two LinearLayouts are for background color control; and the idea with the ImageView and the ScrollView is that my UI should look like this:
+------------+
|TOOLBAR =|
+------------+
| |
| IMAGE |
| |
|111111111111|
|222222222222|
|333333333333|
|444444444444|
+------------+
which should then scroll to
+TOOLBAR----=+
+------------+
| |
| IMAGE |
| |
|111111111111|
|222222222222|
|333333333333|
|444444444444|
|555555555555|
+------------+
and further to
+------------+
| |
| IMAGE |
| |
|111111111111|
|222222222222|
|333333333333|
|444444444444|
|555555555555|
|666666666666|
+------------+
and then to
+------------+
| |
| IMAGE |
| |
|222222222222|
|333333333333|
|444444444444|
|555555555555|
|666666666666|
|777777777777|
+------------+
(with the numbers representing the things in the ScrollView).
The above behaviour I was able to get just by setting
app:layout_scrollFlags="scroll|enterAlways" on the Toolbar as standard. However, if I then start dragging down on the ScrollView, the Toolbar doesn't come back. In fact, I haven't found any way to get the Toolbar back once it has scrolled out.